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Tuning in the slide with opera wheel tuning system, beautiful yellow brass with flat wrap F attachment. Such inventions often threaten to upend the very foundations of scientific disciplines, which is primarily why they have been ignored as they have, if they are not actively suppressed. How general is this? Oxygenic photosynthesis first appears. Of the tree species modeled in DISTRIB, 70 were of interest to the Chicago Wilderness region because they are currently present or expected to gain suitable habitat in the area. A pneumatically driven locking piston ensures that the connection is secure and provides pneumatic and electric pass-through to supply controls to the robot tool.

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Yamaha YBL Xeno, inline rotary valve bass trombone. A well established workhorse of professional level bass trombones. The valve register is even and open, sound quality is focused and projecting. A very easy to use instrument that rewards you. This one is in used condition but has been well maintained. Some normal wear and tear cosmetically.

Includes the original case. Here's a custom made Bach 50 with Rath inline Hagmann valves. This horn was custom put together to be a lightly braced orchestral bass trombone. The valves are made by Rath, have squared off crooks and threaded valve caps. The bell and slide are from a Bach It has been used professionally in a major US symphony orchestra. There are some cosmetic scratches in the bell from some dents that have been removed.

The finish is not perfect. This is one of the most in demand tubas in the world at the moment. Players are snatching these up because they work fantastically well, both for auditions and at work in the orchestra.

It makes a great big sound but retains the clear and clean character that really helps set players enhance their performance. This instrument is brand new and a "Demo" model from a trade show. It is in like new condition and includes a very nice quality gig bag. US shipping is available via Greyhound. The Yamaha v was one of the most popular "Geyer" style french horns made.

It has since been replaced by the newer YFR model but most players still seek out the model v, as they general consensus is that it is a better instrument. They "Geyer" sound, an inline valve block coupled with a medium throat yellow brass horn and open wrap has become the industry standard for French Horns.

It is in very excellent used condition, raw brass, no dents or major cosmetic blems. Ready to play out of the box. Classic Bach 42 with gold brass bell from the s. Plays really great, powerful dense sound and good slotting. Super solid and in great shape. Beautiful and rare Conn 70H bass trombone from the s, with optional E rotary switch valve. This isn't a "Fuchs" Model but the standard smaller throated 70H. It is in great condition, stunning actually.

Tuning in the slide with opera wheel tuning system, beautiful yellow brass with flat wrap F attachment. Its spent most of its life here in Los Angeles and has many years of use left. A unique opportunity to own one of the early custom made instruments by Marc L'Anglier. This one was made in the early s for John Englekes of the San Francisco Symphony and further modified by the next owner who has had it since then.

We believe that there were six L'Anglier bass trombones built, this one being 5 of 6. The bell is from a Corporation 50BGL The slide is an 81xxx serial number, it has had a recent addition of a nickel silver crook. Leadpipe is a Brassark MV50 copper seamed press fit. Most interestingly, this trombone is currently set up with a "Haynor" valve system.

If you look at the photos, you can see how it functions. The concept being that the weight of the instrument is cradled in the palm of your left hand while you pull the levers of the valves towards you. Works well for players that have shoulder trouble or otherwise have issues holding up a bass trombone. This trombone is being sold as is with this Haynor system installed which is very well done btw but we can convert to normal split trigger configuration for a small additional fee if you want it set up normally.

Every once in a while I get something really special and unusual. Here's an early s King 2B Silversonic with all the bells and whistles, the deluxe gold inlay finish. You'd be hard pressed to find a more beautiful trombone than this one. Its in fantastic condition. Sterling silver bell, great slide and original case with documents. Previously owned by Alex Iles. This horn has been well used and shows it. Has some dents, scratches and worn lacquer.

Regardless of this, its quite a good playing trombone and would be great for a player looking for a top tier professional trombone at a bargain price. An underrated pro level trombone, the Benge F is a large bore. It isn't the most fancy or glorious but it does play well and is a very nice instrument for a student or young professional looking for a quality horn that won't break the bank. This one is in very nice shape and silver-plated.

Long the industry standard for the west coast and many professional orchestras around the world. This is a newer Eastlake Conn 8D, good lightly used condition with some minor cosmetic blems and normal wear from use.

A good playing instrument that will serve as a workhorse for many years to come. The 8D was based on the famous Kruspe Horner model. It is a large bore french horn with a large bell flare. Extremely rare German romantic trombone made in the late s by one of the most famous and influential makers of trombones, J.

Penzel was the apprentice of Sattler, who is credited with creating the large bore trombone, and this instrument is made in the same style as those original models. It is gold brass, extremely thin material, with a wide nickel garland that is engraved and decorated with the traditional shell stamps. Interestingly, this particular trombone has a tuning slide incorporated in the slide. I showed it to Robb Stewart who repaired a small crack in one of the slide legs and he and I both believe this is an original feature on this instrument, making it particularly unusual and special.

It's a big bore and takes a mouthpiece somewhere between a "euro" shank and a modern large shank. Slide works well for raw inners which are both original and being as old as it is. A piece of history to use in period work or just to own an important instrument in the evolution of the trombone. This is a terrific playing Bach 42 and has the coveted "Stainless Steel" casing from O.

Thayer that was very popular in the s. Recently restored here at our shop, it has been gently relacquered and some worn parts replaced and repaired. Comes with a press fit Brasslab leadpipe. Honestly, if I didn't have so many trombones, I'd keep this one. I love the sound of it, orchestral but clear and brilliant.

Not going to last long. Own a legend, this is one of Dick Nash's Bach 36 trombones, with a gold brass bell and lightweight brass slide. Dick played this trombone on countless film scores, it's got lots of good notes in it.

A very nice playing Shires bass trombone with dependent trubore valves, one of 9 sets I believe. This is a unique playing trombone, it reminds me a lot of a Holton, that big warm enveloping sound that gets a touch bright when you lay into it. Has an unsoldered red brass bell, B62 slide one leadpipe. My guess is this Ophicleide is from the late s judging by the number of keys and lever system.

It was repadded and corked by Robb Stewart and has quite a nice sound. Chinese Ophi's are ubiquitous now, here's a chance to have an authentic antique for a reasonable price.

A fantastic deal for an inline professional level bass trombone. I just love the sound of a Benge trombone, it is gooey dark with a brilliant edge, begging to be played with core and depth. These are wonderful under appreciated trombones.

This instrument has been in storage at a music shop for the past 15 years. Rumor has it that Larry Minick was involved with the design of this model, could be true. The valves look a lot like a Minick wrap. The H is a great bargain for an inline valve bass trombone. This one has a 10" unlacquered red brass bell, some minor cosmetic and lacquer blems. Makes a great big sound and is fun to play. Totally unique trombone that was built from parts for a Bach aficionado to be an ultimate vintage Bach jazzer.

Robb Stewart fabricated the trombone. Bell flare is from Byron Peebles collection, a Mt Vernon 12 yellow brass bell. The neckpipe is custom built by Robb, along with the hexagonal cross braces, The tuning slide and hand slide are from a Bach New York model A custom knurled hand brace was fabricated by Robb looks kinda steampunk and feels good in the hand.

Comes with a Mt Vernon coffin case. I can't recall the last time I saw one of these in person, if ever. One thing I love about this trombone is the makers stamp, it is an early Mt Vernon so the signature still looks like the New York factory stamp, I love that. It has a dual bore. Also unusual is that this one has gold brass outer slide tubes. In very good vintage condition.

A unique opportunity to purchase something special from arguably the most desirable Bach period of production. This Bach jazzer has some pedigree to it, owned by the late Chauncey Welsch. As such, as with all of Chauncey's trombones, the tuning slide has been slightly shortened to allow for slide vibrato in 1st position, old skool!

The 16GM bell section has a more open neckpipe. This one also has a Bach 12 lightweight nickel silver In good shape with usual wear and press fit leadpipe. A corporation Bach 42B, no frills, just a workhorse.

In good used condition, the finish does have some scratches and lacquer is more or less gone. Makes a nice classic Bach sound. This is a lightly used, gorgeous Miraphone BBb tuba. The has long been the staple of BBb tubas since it was introduced and is the most widely played model BBb in the world.

This particular instrument was picked out at the factory in Germany and imported into the USA. It is in very excellent shape with no major dings and only a few cosmetic scratches and pings. Lacquer is in very good condition. It includes a Winter hard case. Super rare and super gorgeous, this is a Bach New York model 36B. Traditional wrap, larger Marston rotary valve with updated linkage,. Robb Stewart did a beautiful job refurbishing this trombone as a nice touch he made a long water key by request of the owner without buffing destroying the original lacquer on the bell there are a few lacquer blems on the bell.

The leadpipe is removable, and a custom two piece leadpipe is installed. Comes with a period Bach case. This horn is absolutely a gorgeous time capsule.

It is all original with matching serial numbers. It is in fantastic condition for nearing years old. The slide has the original tubes in great shape and the slide action is extremely respectable for a trombone of this vintage.

The hand engraving is jaw dropping gorgeous. Lion head engraving on the slide is also clear and not worn. A well used and well loved Shires trombone, early production! The bell is hand engraved and would become the 1Y bell flare. The horn has a Thayer valve with original nickel shires thumb paddle, the slide is a dual bore. Owned by one of the top jazz trombonists here in LA, this is an extremely nice playing Bach 12 Mt Vernon. Its not in perfect shape cosmetically but it is nicely broken in with lots of strong slots and fast response.

This one reminds me of a baseball glove that your friend has that's perfectly seasoned. Yep, that is this trombone. A nifty Selmer Paris Bolero trombone. Not only is it good for Bolero, it is also good for all sort of commercial playing. It is a versatile size, similar to the King 3B,. A nice touch, the bell has a small brass garland on the rim. These are high quality instruments and a bargain price.

In good used condition with typical wear and tear. A gorgeous vintage Mirafone bass trumpet in Bb with 4 rotary valves. Appropriate for Janacek, Wagner, Stravinsky or any other prominent bass trumpet literature. The sound is beautiful, singing and colorful. Nice intonation and very easy to play. In very good condition and especially rare to find these with 4v.

Includes a very nice lightweight nylon gig bag. This was the Ralph Sauer setup for many years before Ralph switched to his Shires with similar specs. The 88HTO has an open wrap F attachment and thin red brass bell flare.

The SL slide is a dual bore. It is in very good, lightly used shape and is an excellent player. Perfect for the trombonist looking for a large orchestral sound but something that speaks a bit faster and is a bit more nimble than a full. This one is a bell tuning model and measures to a. The engraving is all hand done and features Earl's bulldog on the bell.

Overall the trombone has seen better days and is in need of some love and repairs to be completely playable again at a professional level. As such, it is priced low with he hopes that someone will invest in bringing this rare instrument back to life. This Shires bass trombone is a few years old and remains in very good condition. A really great playing instrument that is versatile and comfortable.

A uniquely unusual renaissance instrument, the tenor cornett aka Lizard, Lysarden, Lysard. This one is unstamped but extremely well made and high quality wood, wrapped in traditional black leather. It is in D with a key for C. Includes a mouthpiece made of horn. Sure to impress your friends and audiences alike.

Here is a nice workhorse Bach LT16M trombone. It has an open neckpiece, lightweight nickel slide and a one piece yellow brass bell. The model made famous by Bill Watrous.

This one is in excellent shape and ready to play. Here's a well used Shires Bass Trombone. A good solid playing instrument, priced to sell. There are some scratches, lacquer wear and signs of use but don't let that deter you, its just cosmetic. Here is something really unique and amazing! This is a custom made Thein bass trombone and has great features and specs.

The F attachment is a Hagmann valve, a custom removable 2nd valve was fabricated to fit and works extremely well. The main tuning slide is from a shires and has been custom fit to this instrument to give it a more "American" blow and response.

The instrument also includes a single valve F tuning slide. In great condition, lacquer on the bell is frosted from being in a cold climate. Comes with a Thein flat screw bell case. Probably the best playing pocket tuba in the world. Here is a BBb pocket tuba from Manfred Schmelzer. This is by far the best design for a small "tornister tuba" I've seen so far and that is because of its full length leadpipe and impressive large bore bends. This is the ultimate pit tuba.

If you are a doubler and need a great playing BBb that you can take to work for your show work, this is the one. Or if you're looking for a really good playing tuba that you can take on the road with minimal space, this is it. It was a demo model from the recent ITF International Trombone Festival in Redlands, and is new but did have a small mishap with the airlines during transit to the show and there is a small ding in the bell flare.

As such, get it at a good discount. Silver plated with gold plated trim. Get a great deal on this brand new Yamaha Xeno bass trombone. This one was a demo model and is in perfect condition, with some minor scratches on the outside of the case only.

Comes with original mouthpiece. Beautiful like new Kanstul bass trombone. Modeled after the vintage Conn 62H trombones, this Kanstul features "tuning in the slide", fully conical back bow, thin red brass bell, wide slide and free blowing CR valves.

Very nice instrument indeed. One gold brass leadpipe included. One of the most desirable medium bore trombones in the world. Up for sale, an Earl Williams model 8 trombone in excellent condition. This instrument was made in the late s by Earl's son, Bob Williams at the Burbank shop. It has an 8. It blows like a jazzer but sounds like a big horn.

If you're looking for a commercial trombone that has a big sound, this is the one. This one is really a beautiful instrument, has a silver plated slide, lacquered bell. Slide action is great. The bell flare is very thin and lightweight. Lots of fast notes still left in it. Bob is extremely picky about his trombones and he's owned this one for many years.

There is a smallpre-emptive patch on the bell rim, as the metal is thin there and Bob didn't want the rim to split. A great playing vintage Bach 42B "Corporation" from the early s. Features the larger Marston made rotary valve same valve on the Mt Vernons with a closed wrap.

Silver finish in decent shape, some silver is worn through showing brass on the neckpipe which you can see in the photos easily covered up with a leather neck guard. This 42 has one of the sweetest and clearest tones of 42s that have come through the shop. Really a beautiful blowing and sounding instrument. We had a beautiful vintage Elkhart Conn 88H come into the shop and thought it would be a nice candidate for a full conversion. We decided to leave the closed wrap intact to preserve the vintage feel but install our new modern rotary valve.

The closed wrap also has our custom ferrules installed. The bell has had Don's voodoo treatment, new slide crook and our custom Brassark BA2 leadpipe, which is a nice match to the instrument. Threaded leadpipe receiver has been installed and fits Shires threads.

We decided to leave the slide the original "narrow" width of an 88H. The instrument was then lightly buffed and relacquered. A top tier Conn 88H with our well balanced rotary valve that gives vast improvement on the F side of the instrument.

This one projects like crazy, big warm sound with clarity and color. Here is a brand new demo Schilke model ST30 trombone. Think like a Conn 6H that's been pimped out. Quality and craftsmanship is very nice and it feels good in the hand. Includes a Schilke hard case. Here is a very cool setup, an Edwards T finished in brushed lacquer with two bell flares, one yellow brass and one red brass. Includes a newish protec case as well.

The yellow bell is a CF and the red bell is a CF. The condition is excellent on this trombone and it is a great playing jazzer. Rare Burbank Earl Williams model 6 trombone,. This one was made by Bob Williams, Earl's son. The outer tubes and leadpipe are from a Conn H there is a small patch on the bottom tube. The bell is unstamped but is obviously original to the horn and authentic Williams. As such, price reflects so this is a bargain for a monster playing Williams.

In near factory condition. Get a bargain on this horn. A very nice "L series" Conn 8D professional french horn, raw nickel silver. In very good condition. There is a small patch in the flare shown in photo. The valves have been plated and are sealing well.

Includes a leather Marcus Bonna case. A very rare gem of a bass trombone, this instrument was purchased new in and immediately modified by Larry Minick into the configuration you see here. He built the inline valve section as well as installing an unstamped 62H bell flare that Minick was certain was an improvement over the original bell flare, it was installed and remains on this instrument. The original leadpipe and Minick Leadpipes are included. The valve configuration is inline: It has been used for many years and shows that is has but overall is in very good condition with a lot of life left.

This thing is a gas to play, its everything you expect it to be and more. These rarely show up for sale and I can speculate that the inline Minick bass trombones are fewer than you can count on your hand. Stunning vintage Bach Mt Vernon 50B with inline hangman valves. We built this instrument here at The Brass Ark for one of our clients. The valve section is an inline progressive bore with rose brass tubing. One of the nicest bass trombones we've ever had at the shop. Included with the instrument is the original MV case no longer fits this wrap and the original single valve parts.

Extremely rare jazz trombone made by the legendary trombone builder, Earl Williams. This instrument is one of the earliest stamped model 4 trombones I've seen. It was made at the Los Angeles shop and still has the prominent "williams" trademarks: It was fully restored in by Robb Stewart.

Robb fabricated new cork barrels to match the original as well as rotated the inner tubes to extend the life of them. He also did a nice patch on the original slide crook. It was buffed and relacquered by Robb. This is a stunning trombone and one of the very best jazzers I've ever played.

Beautiful lightly used Edwards TE. This one has some unique specs! Comes with three leadpipes and a sterling silver T3 leadpipe.

A very nice Edwards fiberglass lightweight case is included. Here's a nice miraphone model BBb tuba with 4 rotary valves. It has had some repairs and shows cosmetic blems in the lacquer as well as some scratching in the finish. Nice quality tuba that's functioning as it should. The valve linkages have been upgraded to minibal style. A winter style hardcase with wheels is included.

This is a great deal on a top level professional CC tuba. Overall the instrument is in nice used condition. It does have worn spots through the silver and there are some small dings and dents. It is a very solid player with excellent intonation.

The low register has a nice powerful sound that blends nicely in ensemble. Nearly new condition professional double French horn made by Mark Atkinson in Burbank. It is all nickel silver and has a Kruspe valve wrap.

It is a Geyer style wrap with a medium throat bell and built from rose brass. This instrument came directly from Conn and has not been previously owned. It has a cut bell and comes with the original Conn case. Alexander, a top tier maker. This instrument is gorgeous and has a beautiful descant tone, ultra clear and bright with lots of colors. In overall very good used condition with tight valves. Comes with a cut bell case. A very nice Conn 4H in the rare satin silver finish. Previously owned by Alex Iles of the LA studio scene.

Extremely good player and in very good condition. Here's an Elkhart Conn 6H. It was owned by Alex Iles. There are some dents and some serious slide wear to the inner tubes. A nice player though it needs some love. Older Yamaha YEP 4 valve euphonium. Previously owned by Alex Iles of the LA studios. This instrument has had a Minick style tuning trigger added on the main slide to help with tuning on the fly.

Overall in very good used condition. Professional Jupiter Jazzer trombone, previously owned by Alex Iles. This model has a. These Jupiter trombones are becoming very popular. This one has a gold brass bell flare and plays well.

Hip Jazz trombone developed back in the s with John Fedchock. This particular instrument was owned previously by Alex Iles. It is in nice used condition and ready to play. Somewhat rare, this is a Bach model 36GO, gold brass bell flare and open wrap valve. In very nice condition with case. A great playing instrument that is a versatile size. Good for symphonic literature as well as commercial applications. Extremely rare bass trombone made by the famous maker, Larry Minick.

This one appears to be a purpose built instrument, in that it wasn't another instrument before like a modified 62H. It has a one piece Minick bell flare, the valves are dependent and also stamped.

The J bend tuning slide is prominent in the design and the slide also appears to be custom made. The valves are tuned as normal in F and D. The leadpipe is press fit, but has corroded and should be replaced.

This is a killer instrument and I've only seen a handful ever. A unique opportunity to have one of the most coveted bass trombones in the world. Made in the mid s in England not a Music Group made Besson , this euphonium has the sweetest sound. I had Brad Close make and install a custom standard large shank mouthpiece receiver so it takes a normal mouthpiece. Bob Reeves did a full valve alignment. It is very clean, a few small dings and some lacquer scratches.

Comes with a nice form fitting hard case. Rare eB alto trombone made by J. Model 3, which is the large bore. I don't know why it works so well, but despite the size of this alto, it doesn't sound like a tenor trombone. Its a fabulous sounding and looking instrument, very high quality craftsmanship. Nickel silver bell garland and nickel slide. This is a new demo model that was assembled from parts that were shown at a trade show.

It looks nearly new with a few small blems in the lacquer. Really a tremendous playing shires. This is an unusual but very special trombone. The model 45 is a special order dual bore small bass trombone.

It has a 9" gold brass bell, open wrap F attachment and narrow width dual bore. This particular instrument was hand assembled from parts at the Bach factory with assistance from Joe Alessi.

It has had two owners and is in good condition. I've not seen another one like this before. Custom made Edwards bass trombone with a s Corporation Bach 50 bell flare. The court rejected this approach, finding that OSHA failed to make industry-specific findings or identify the specific technologies capable of meeting the proposed limit in industry-specific operations.

While OSHA had identified primary air contaminant control methods: Engineering controls, administrative controls and work practices and personal protective equipment, the agency, "only provided a general description of how the generic engineering controls might be used in the given sector. Though noting that OSHA need only provide evidence sufficient to justify a "general presumption of feasibility," the court held that this "does not grant OSHA license to make overbroad generalities as to feasibility or to group large categories of industries together without some explanation of why findings for the group adequately represents the different industries in that group.

The court rejected OSHA's economic feasibility findings for similar reasons. As discussed above, OSHA supported its economic feasibility findings for the Air Contaminants rule based primarily on the results of a survey of over businesses, summarizing the projected cost of compliance at the two-digit SIC industry sector level.

The court held that OSHA was required to show that the rule was economically feasible on an industry-by industry basis, and that OSHA had not shown that its analyses at the two-digit SIC industry sector level were appropriate to meet this burden.

While OSHA might "find and explain that certain impacts and standards do apply to entire sectors of an industry" if "coupled with a showing that there are no disproportionately affected industries within the group," OSHA had not explained why its use of such a "broad grouping was appropriate. The set of resulting analytical approaches OSHA has engaged in is highly resource-intensive and has constrained OSHA's ability to prioritize its regulatory efforts based on risk of harm to workers.

In , OSHA made its first attempt following the Air Contaminants ruling to update a smaller number of PELs using a more rigorous analysis of risk, workplace exposures, and technological and economic feasibility. Sixty priority substances were identified for further examination and twenty of the sixty substances were selected to form a priority list. Early in , the Agency announced its plans for a stakeholder meeting, and identified the twenty priority substances, as well as several risk-related discussion topics.

Overall, many of the stakeholders did not support the development of a list of priority chemicals targeted for potential regulation and felt there was a lack of transparency in the process for selecting the initial chemicals.

In response to stakeholder input and OSHA's research, the agency selected seven of the 20 substances discussed at the stakeholder meeting for detailed analysis of risks and feasibility.

The chemicals selected were: Quantitative risk assessments were performed in-house, and research including site visits was undertaken to collect detailed data on uses, worker exposures, exposure control technology effectiveness, and economic characteristics of affected industries.

The research and analysis were carried out over several years, after which OSHA decided not to proceed with rulemaking. Although the project did not result in a rulemaking to revise the PELs, OSHA gained valuable experience in developing useful approaches for quantifying non-cancer health risks through collaboration with external reviewers in scientific peer reviews of its risk analyses. OSHA is now examining ways to better address chemical exposures given current resource constraints and regulatory limitations.

For readers who are interested in a more detailed account of the legislation and court decisions that shaped OSHA's current regulatory framework, Appendix A to this Request for Information, History, Legal Background and Significant Court Decisions, provides additional information.

Readers may want to consult Appendix A as they frame responses to the questions posed in this Request for Information. This section reviews how interpretation of 6 b 5 and subsequent case law has resulted in the methods it uses when developing risk, technical feasibility, and economic findings as well as the evidence OSHA has used in the past to make these findings i.

This section also reviews developments in science and technology and how these new advancements may improve the scientific basis for making findings of significant risk, technical feasibility, and economic feasibility. As an example, the National Academies of Science has released extensive reviews of advances in science, toxicology, and risk and exposure assessment and evaluated how the Federal government can potentially utilize these advancements in its decision-making processes NRC, ; Ex.

While new technologies will advance the public's understanding in these critical areas, the Agency has obligations under the OSH Act to make certain findings under 6 b 5 , as discussed above in Section III. How OSHA might utilize these new developments to meet the Agency's evidentiary burden will be discussed in this section.

While the Court did not stipulate a means to distinguish significant from insignificant risks, it broadly described the range of risks OSHA might determine to be significant: It is the Agency's responsibility to determine in the first instance what it considers to be a "significant" risk.

Some risks are plainly acceptable and others are plainly unacceptable. If, for example, the odds are one in a billion that a person will die from cancer by taking a drink of chlorinated water, the risk clearly could not be considered significant.

On the other hand, if the odds are one in a thousand that regular inhalation of gasoline vapors that are 2 percent benzene will be fatal, a reasonable person might well consider the risk significant and take the appropriate steps to decrease or eliminate it. Because this risk exceeds the value of one case of lung cancer per exposed workers, OSHA found it to be significant.

The significance of risk determinations of other rules since the Benzene decision have typically followed a similar logic. Over the three decades since the Benzene decision, OSHA has gradually built up a highly rigorous approach to derive quantitative estimates of risk such as those found in the hexavalent chromium preamble.

First, the Agency reviews the available exposure-response data for a chemical of interest. It evaluates the available data sets and identifies those best suited for quantitative analysis. Using the best available data, the Agency then conducts extensive statistical analyses to develop an exposure-response model that is able to extrapolate probability of disease at exposures below the observed data.

Once the model is developed, OSHA conducts further analyses to evaluate the sensitivity of the model to error and uncertainties in the modeling inputs and approach. The exposure-response model is used to generate estimates of risk associated with a working lifetime of occupational exposure to the chemical of interest over a range of PEL options that often include exposure levels below those considered to be technologically feasible.

The entire risk assessment has always been subject to peer review, from choice of data set s through generation of lifetime risk estimates. When the proposed rule is released for comment, it receives additional scrutiny from the scientific community, stakeholders, and the general public.

The Agency uses the feedback of the peer review panel and public comment at the time of proposal to further test and develop the risk analysis. This model-based approach to risk assessment has a number of important advantages. The quantitative risk estimates can be easily compared with the level of 1 in that the Court cited as an example of significant risk.

Sometimes, the best available data come from worker or animal populations with exposure levels far above the technologically feasible levels for which OSHA must evaluate risk, and a risk model is used to extrapolate from high to low exposures.

When large, high-quality exposure-response data sets are available, a rigorous quantitative analysis can yield robust and fairly precise risk estimates to inform public understanding and debate about the health benefits of a new or revised regulation.

However, there are also drawbacks to the model-based approach, and there are situations where a modeling analysis may not be necessary or appropriate for OSHA to make the significance of risk determination to support a new or revised regulation. Model-based risk analyses tend to require a great deal of Agency time and resources. In some cases, the model-based approach is essential to OSHA's significant risk determination, because it is not evident prior to a modeling analysis whether there is significant risk at current and technologically-feasible exposures.

In other cases, however, it may be evident from the scientific literature or other readily available evidence that risk at the existing PEL is clearly significant and that it can be substantially reduced by a more stringent regulation without the need for quantitative estimates extrapolated from an exposure- response model. In addition to reducing significant risk of harm, the OSH Act also directs the Agency to determine that health standards for toxic chemicals are feasible.

At times, it is evident without extensive analysis that the most stringent PEL feasible can only reduce, not eliminate, significant risk.

In such cases, the value of a model-based quantitative risk assessment may not warrant the Agency time and resources that model-based risk assessment requires. In situations described above where the PEL may be set at the lowest feasible level, OSHA believes that it can establish significant risk more efficiently instead of relying on probabilistic estimates from dose-response modeling as described above.

OSHA is exploring a number of more flexible, scientifically accepted approaches that may streamline the risk assessment process and increase the capacity to address a greater number of chemicals. OSHA seeks input on the risk assessment process described above.

When is a model-based analysis necessary or appropriate to determine significance of risk and to select a new or revised PEL? When should simpler approaches be employed? Are there specific approaches OSHA should consider using when a model-based analysis is not required?

To the extent possible, please provide detailed explanation and examples of situations when a model-based risk analysis is or is not necessary to determine significance of risk and to develop a new standard. General Description and Rationale of Tiered Approach OSHA is considering a tiered process to exposure-response assessment that may enable the agency to more efficiently make the significant risk findings needed to establish acceptable PELs for larger numbers of workplace chemicals.

The approach involves three stages: The first step is dose-response analysis in the observed range. During this step, OSHA analyzes exposures or doses and adverse outcomes from human studies or animal bioassays, particularly at the lower end of the exposure range.

The second step is margin of exposure determination, where LETEs are compared with the range of possible exposure limits that OSHA believes to be feasible for the new or proposed standard.

Typically, there is a close and ongoing dialogue between those OSHA technical staff and management responsible for the risk assessment and their counterparts responsible for the feasibility analyses as the separate determinations are being simultaneously developed.

Feasibility analyses, in particular, can take years of research, including site visits and industry surveys. Thus, OSHA sets many PELs at the lowest feasible level, and not at a level of occupational exposure considered to be without significant risk. This significant risk orientation differs from other Federal Agencies, such as EPA and ATSDR that set environmental exposure levels determined to be health protective without consideration of feasibility.

If the MOE indicates the range of feasible exposures is in close proximity to the exposures where toxicity is observed i. In this situation, OSHA would set the PEL at the exposure level it determines to be feasible and the dose-response analysis in the observed range should be sufficient to support Agency significant risk findings.

The PEL is set at the lowest feasible level, with the understanding that significant risk of adverse health outcomes remains at the new PEL.

In the traditional risk assessment approach described previously, OSHA uses quantitative exposure-response modeling to estimate risks below the range of observed exposure, without regard to whether such exposures are considered to be technologically feasible. If the lowest technologically feasible workplace exposures are determined to be far below the LETE i. If there is a high MOE, then the Agency would move onto the final stage of the tiered approach, which is exposure-response extrapolation, where the dose-response relationship is extrapolated outside the observed range.

Many regulatory agencies, such as EPA, choose to extrapolate outside the observed range for non-cancer health outcomes by applying a series of extrapolation factors, also called uncertainty factors, to an observed low-end toxicity value, referred to as a point of departure POD.

The distinction between these toxicity values is discussed later in the subsection. The extrapolation factors are further explained below. In many instances, EPA does not use the extrapolation factor approach for cancer effects. Rather, EPA uses dose-response modeling in the observed range and a linear extrapolation below the observed range to derive a unit risk i.

As described previously, OSHA also uses dose-response modeling to extrapolate risk below the observed range for carcinogens as was done for hexavalent chromium 71 FR ; Ex. There is a reasonable body of scientific evidence that genotoxic carcinogens, and perhaps other carcinogenic modes of action, display linear, non-threshold behavior at very low dose levels.

OSHA also uses dose-response modeling to extrapolate risk below the observed range for carcinogens. As mentioned earlier, the Agency develops appropriate exposure-response models linear or non-linear that best fit the existing data and are consistent with available information on mode of action.

The models can be used to extrapolate risk associated with a working lifetime at occupational exposures below the observed range. In some situations, the LETE is further adjusted to calculate worker equivalent exposures and to account for how the chemical is absorbed, distributed, and metabolized, and interacts with target tissues in the body.

These features and other important issues related to the tiered approach to exposure-response assessment are discussed below. OSHA believes that there are a number of potential advantages to using a tiered risk assessment framework including opportunities to rely more heavily on peer-reviewed risk assessments already prepared by other Federal agencies.

In conducting a hazard identification, OSHA evaluates individual study quality and determines the weight of evidence from epidemiological, experimental, and supporting data. OSHA gives weight to both positive and negative studies according to study quality when the Agency evaluates the association between chemical agent and an adverse health effect. In its review of the available evidence, OSHA assesses the chemical's modes of action MOA and the key molecular, biological, pathological, and clinical endpoints that contribute to the health effects of concern.

The Mode of Action MOA is a sequence of key events and processes starting with the interaction of the agent with a molecular or cellular target s and proceeding through operational and anatomical changes that result in an adverse health effect s of concern. The key events are empirically measurable molecular or pathological endpoints and outcomes in experimental systems.

These represent necessary precursor steps or biologically-based markers along the progression to frank illness and injury. MOA informs selection of appropriate toxicity-related endpoints and models for dose-response analysis. OSHA then conducts a dose-response analysis for critical health effects determined to be associated with a chemical, provided there are suitable data available.

Dose-response analysis requires quantitative measures of both exposure and toxicity- related endpoints. OSHA gives preference to studies with relevant occupational routes that display a well-defined dose-related change in response with adequate power to detect effects at the exposure levels of interest. The Agency generally prefers high quality epidemiologic studies for dose-response analysis over experimental animal models, provided there is adequate exposure information and confounding factors are appropriately controlled.

OSHA may only adopt standards for exposure to "toxic materials and harmful physical agents" that causes "material impairment of health and loss of functional capacity even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life. This includes key molecular and cellular biomarkers established as necessary precursor events along a critical disease pathway.

It is important that the toxicity-related endpoints observed in experimental animals selected for dose-response analysis have relevance to humans and are not unique to the test species. In the past, OSHA, for the most part, has undertaken an independent evaluation of the evidence in its identification of hazards and selection of critical studies and toxicity-related endpoints for dose- response analysis. However, other Federal agencies use the same risk assessment framework with similar hazard identification and dose- response selection procedures.

These assessments undergo scientific peer review and are subject to public comment. The Agency is considering ways to reduce the time and resources needed to independently evaluate the available study data by placing greater reliance on the efforts of other credible scientific organizations. Although some organizations use their study evaluations to support non-occupational risk assessments, OSHA believes that, in most cases, these evaluations can be adapted to the occupational context.

If so, what is the basis and process for establishing the OEL? Do you use an authoritative source, or do you conduct a risk assessment? If so, what sources and risk assessment approaches are applied? For example, is rigorous scientific peer review of the OEL an important factor? Is transparency of how the OEL was developed important? What advantages and disadvantages would result from this approach and could it be used in support of the PEL update process?

Derivation of Low-End Toxicity Exposure LETE An important aspect of the dose-response analysis is the determination of exposures that can result in adverse outcomes of interest. For most studies, response rates ranging from 1 to 10 percent represent the low end of the observed range.

Epidemiologic studies generally are larger and can show a lower observed response rate than animal studies, which typically have fewer test subjects. This dose is referred to as the POD 'point of departure' because it is used as a starting point for low dose extrapolation or the application of uncertainty factors as described above to derive toxicity values. However, OSHA does not intend to use the LETE as the point of extrapolation for determining a "safe" exposure level in the manner used by the aforementioned agencies.

The BMD approach uses a standard set of empirical models to determine the dose associated with a pre-selected benchmark response BMR level. An example is the dose associated with a 10 percent incidence i. Selection of an appropriate BMR considers biologic as well as statistical factors and a lower BMR is typically applied for clinically serious outcomes e. In some cases, more sophisticated models can be used in the LETE determination, based on physiologically-based toxicokinetics, toxicodynamics, or dosimetry models that relate the administered dose to a more toxicologically relevant dose metric at a biological target site, if sufficient data is available and the models are appropriately validated.

This is discussed further below. In many situations, the LETE must be adjusted to represent a typical worker exposure. Allometric scaling refers to scaling physiological rates and quantities to mass or volume of one animal species to another animal species. Many physiological and biochemical processes such as heart rate, basal metabolic rate, and respiration rate have been found to have a scaling component of 0. Allometric scaling is most applicable when the toxicologically relevant dose is a parent compound or stable metabolite whose absorption rate and clearance from the target site is controlled primarily by first order processes.

Allometric scaling is less well suited for portal-of-entry effects or when toxicity is a consequence of a highly reactive compound or metabolite. Portal of entry refers to the tissue or organ of first contact between the biological system and the agent.

This is nasal, respiratory tract and pulmonary tissues for inhalation; skin for dermal contact, and mouth and digestive tract for oral exposure. In the case of respiratory tract effects from inhalation, EPA recommends adjusting inhalation doses based on generic dosimetry modeling that depends on the form of the chemical e.

For example, the human equivalent for a reactive gas that exerts its toxic effect on the respiratory tract is scaled based on animal to human differences in ventilation rate and regional surface area of the respiratory tract.

On the other hand, the dosimetry model adjustment for an insoluble gas that exerts its effect in a tissue remote from the lung is scaled by species differences in the blood: The generic dosimetry models can accommodate specific chemical data, if available.

The models are only intended to account for human-to-animal differences in bioavailability and further allometric or extrapolation factors may be needed to account for species differences in metabolic activation and toxicodynamics i. Several methodologies have been utilized to adjust critical study exposures to a worker equivalent under representative occupational exposure conditions including standard ventilation rates, allometric scaling, and toxicokinetic modeling.

What are reasonable and acceptable methods to determine worker equivalent exposure concentrations, especially from studies in animals or other experimental systems? The worker-adjusted LETE that is derived from dose-response analysis in the observed range should be regarded as a chemical exposure level that leads to significant risk of harm. In most cases, the LETE is expected to elicit a toxic response in 1 to 10 percent of the worker population. This approximates an excess risk of 10 to cases of impairment per exposed workers over a duration that is typically less than a year working life.

This degree of risk would exceed the 1 per probability that OSHA historically regards as a clearly significant risk. Therefore, Agency risk assessments are directed at determining significant risk at these feasible exposures. Because of the feasibility constraints, low dose extrapolation is not always needed to make the required risk findings. NIOSH also develops workplace exposure limits.

These recommended exposure limits RELs are based on risk evaluations using human or animal health effects data. The exposure levels that can be achieved by engineering controls and measured by analytical techniques are considered in the development of RELs, but the recommended levels are often below what OSHA regards as technologically feasible. A MOE approach can assist in determining the need to extrapolate risk below the observed range.

A large MOE i. This situation would require low-dose risk extrapolation to determine whether technologically feasible exposures lead to significant risk. In this situation, OSHA would set the PEL at the exposure level it determines to be feasible and the dose- response analysis in the observed range should be sufficient to support Agency significant risk findings.

There are several factors that OSHA would need to consider in order to find that the MOE is adequate to avoid low-dose risk extrapolation. These include the nature of the adverse outcome, the magnitude of the effect, the methodological designs and experimental models of the selected studies, the exposure metric associated with the outcome, and the exposure period over which the outcome was studied.

OSHA may regard a larger MOE as acceptable to avoid the need for low-dose extrapolation for serious clinical effects than a less serious subclinical outcome. A larger MOE may also be found acceptable for irreversible health outcomes that continue to progress with continued exposure and respond poorly to treatment than reversible health outcomes that do not progress with further exposure.

Health outcomes that relate to cumulative exposures would tolerate higher MOEs than similar outcomes unrelated to cumulative exposure, especially in short-term studies. In some instances, an adverse outcome observed in experimental animals would tolerate higher MOEs than the same response in a human study that more closely resembles the occupational situation. Other Federal agencies apply the MOE approach as part of the risk assessment process.

In its report on the appropriate uses of risk assessment and risk management in federal regulatory programs, the Presidential Commission on Risk Assessment and Risk Management recommended MOE as an approach that provides a common metric for comparing health risks across different toxicities and public health programs PCRARM, ; Ex.

Is this a reasonable means of determining if further low dose extrapolation methods are needed to meet agency significant risk findings?

What other approaches should be considered? Extrapolation Below the Observed Range The last step in the tiered approach is extrapolation of risk below the observed range. This low-dose extrapolation would only be needed if the MOE is sufficiently high to warrant further dose-response analysis.

This situation occurs when technologically feasible exposures are far below the LETE and quantitative estimates of risk could be highly informative in the determination of significant risk. As described in subsection A. Depending on the nature of the exposure-response data, the Agency has relied on a wide range of different models that have included linear relative risk e. Probabilistic risk models can require considerable time and resources to construct, parameterize, and statistically verify against appropriate study data, especially for a large number of chemical substances.

As mentioned previously, several government authorities responsible for managing the risk to human populations posed by hazardous chemicals commonly use the computationally less complex uncertainty factor approach to extrapolate dose-response below the observed range.

The uncertainty factors account for variability in response within the human population, uncertainty with regard to the differences between experimental animals and humans, and uncertainty associated with various other data inferences made in the assessment. For each of these considerations, a numerical value is assigned and the point of departure is divided by the product of all applied uncertainty factors.

The result is an exposure level considered to be without appreciable risk. OSHA attempted to apply uncertainty factors in the Air Contaminants Rule to ensure that new PELs were set at levels that were sufficiently below exposures observed to cause health effects. The Eleventh Circuit ruled that OSHA had failed to show how uncertainty factors addressed the extent of risk posed by individual substances and that similarly, OSHA failed to explain the method it used to derive the safety factors.

Air Contaminants F. The scientific considerations for applying individual factors have been carefully articulated by EPA and other scientific authorities in various guidance materials EPA, ; Ex. For some factors under certain circumstances, it is being proposed that standard 'default' values can be replaced with 'data-driven' values EPA, ; Ex.

However, the type and magnitude of the uncertainty factor employed for any individual substance still requires a degree of scientific judgment. The methodology does not provide quantitative exposure-specific estimates of risk, such as one in a thousand, that can readily be compared to the significant risk probabilities discussed in the Benzene decision. The National Research Council's Science and Decisions report recently advocated a dose-response framework that provides quantitative risk estimates by applying distributions instead of 'single value' factors NRC, ; Ex.

The critical extrapolation factors, such as species differences in toxic response at equivalent target doses and inter-individual variability in the human population are defined by lognormal distribution with an estimated standard deviation. This allows the human equivalent LETE to be derived in terms of a median and statistical lower confidence bound. The distributional nature of the analysis facilitates extrapolation in terms of a probabilistic projection of average and upper bound risk at specific exposures, such as X number of individuals projected to develop disease out of workers exposed to Z level of a toxic substance within some confidence level Y.

The NRC report describes several different conceptual models with case examples and extrapolation factor distribution calculations NRC, ; Ex. Can the uncertainty factor methodology for extrapolating below the observed range for non-cancer effects be successfully adapted by OSHA to streamline its risk assessment process for the purpose of setting updated PELs?

Why or why not? Are there advantages and disadvantages to applying extrapolation factor distributions rather than single uncertainty factor values? Please explain your reasoning. Chemical Grouping for Risk Assessment OSHA is also considering the use of one or more chemical grouping approaches to expedite the risk assessment process.

In certain cases, it may be appropriate to extrapolate data about one chemical across a group or category of similar chemicals. These approaches are discussed below. Background on Chemical Grouping The term 'grouping' or 'chemical grouping' describes the general approach to assessing more than one chemical at the same time.

It can include formation of a chemical category or identification of a chemical analogue OECD, ; Ex. Chemical categories or analogues can be based on the structural relationship between the chemicals being grouped. Structure-activity relationships SAR are relationships between a compound's chemical structure and physicochemical properties and its biological effects e.

A chemical category is selected based on the hypothesis that the properties of a series of chemicals with common features will show coherent trends in their physical-chemical properties, and more importantly, in their toxicological effects OECD, ; Ex. The use of a category approach means that it is possible to identify chemical properties which are common to at least some members of the category.

This approach provides a basis for establishing trends in properties across that category and extends the measured data e. In the category approach, not every chemical in a group needs to have exposure-response data in order to be evaluated. Rather, the overall data for the category as a whole must prove adequate to support a risk assessment.

The overall data set must allow for an assessment of risk for the compounds and adverse outcomes that lack adequate study. Chemicals may be grouped for risk assessment based on the following: Common functional group e. Within a chemical category, data gaps may be filled by read-across, trend analysis and Quantitative Structure-Activity Relationships QSARs and threshold of toxicological concern.

In some cases, an effect can be present for some but not all members of the category. An example is the glycol ethers, where the lower carbon chain length members of the category indicate reproductive toxicity but the higher carbon chain length members of the category do not. In other cases, the category may show a consistent trend where the resulting potencies lead to different classifications OECD, ; Ex. Methods of Gap Analysis and Filling As a result of grouping chemicals based on similarities determined when employing the various techniques as described above, data gap filling in a chemical category can be carried out by applying one or more of the following procedures: Read-Across Method The read-across approach uses endpoint information for one chemical the source chemical to predict the same endpoint for another chemical the target chemical , which is considered to be "similar" in some way usually on the basis of structural similarity or on the basis of the same mode or mechanisms of action.

Read-across methods have been used to assess physicochemical properties and toxicity in a qualitative or quantitative manner. First, because climate change inherently adds complexity and un- certainty to the process of making forest management decisions, there is no single "answer" for how managers should address climate change in management. Additionally, differences in existing management goals and values will naturally result in a diversity of adaptation actions.

Rather than providing recommendations or prescriptive actions, we designed a flexible approach that accommodates a diversity of management goals, forest ecosystems, ownership types, and spatial scales Swanston and Janowiak Given the need to consider incomplete information and to "learn by doing," adaptive management principles are well-suited for incorporating climate change considerations into management.

Although no active management is currently planned in these stands, swamp white oak Quercus bicolor and bur oak Quercus macrocarpa were identified as two potential species that could be planted in lowland hardwood forests to maintain forest cover if intervention was deemed necessary. These species are not currently present on the property but can be found in localized areas in northern Wisconsin, which would represent a small degree of assisted migration.

Forest Service Although "assisted migration" is rarely mentioned in this report, the need for it is evident, particularly in the description of how the species mix is expected to shift: Boreal species such as quaking aspen, paper birch, tamarack, and black spruce are projected to decrease in suitable habitat and biomass across the assessment area.

Species with ranges that extend to the south such as American basswood, black cherry, northern red oak, and eastern white pine may increase in suitable habitat and biomass across the assessment area. Although "assisted migration" is only slighted mentioned in this report, it will be apparent to all knowledgeable readers that such assistance will be vital in this region. Notably, the boreal tree species with their southern-most current ranges in this region will greatly diminish or entirely wink out, so more southerly species will need to be introduced to ensure multi-layer forest health.

These species are currently very common across the landscape and play a dominant role in many forests, and the reduction of suitable habitat for these species may affect a large portion of northern Wisconsin and the western Upper Peninsula. Report excerpt at right: Balsam fir, black ash, paper birch, and tamarack also have low modifying factor scores, suggesting that there are life-history traits or biological stressors that may cause these species to lose even more suitable habitat than the model results indicate.

A given species will not necessarily be able to migrate to newly available habitat and colonize successfully, however. Species not currently present in the assessment area would require long-distance migration, whether intentional or unintentional, to occupy suitable habitat in the assessment area.

Because the Great Lakes and the Straits of Mackinac present substantial barriers to migration, southern species may be even less able to occupy suitable habitat in the eastern Upper Peninsula.

Habitat fragmentation and the limited dispersal ability of seeds could also hinder the northward movement of the more southerly species, despite the increase in habitat suitability.

Most species can be expected to migrate more slowly than their habitats will shift. Of course, human-assisted migration is a possibility for some species and is expected to become tested and used during the next decades. Click left chart for a short pdf by the forestry extension service, Michigan State University.

USDA regional report A major transition in forest composition is not expected to occur in the coming decades. Global warming is expected to occur with strong latitudinal differences: Projected shifts in habitat suitability for P. Red, yellow, blue and green represent lost, threatened, persistent and emergent habitat, respectively.

Approximately 56 per cent of the contemporary distribution is predicted to be lost or threatened habitat by Mapped projections indicate the shift in the trailing edge encompasses the entire managed boreal forest in Canada. Emergent suitable habitat totalled 28 per cent. Projections of the ecological genetic model into the climate of the decade centered on indicate the challenge for forest management is in assuring a timely transfer of trailing edge populations to the future location of the climates for which they are optimally suited.

Seed deployment zones for P. Each zone identifies a geographic area defined by two non-overlapping confidence intervals 7. Where and when to plant long-lived tree species in a rapidly changing climate may be one of the most significant and perplexing components of forest management.

Historically, geographically-based seed transfer guidelines have been used in reforestation to manage the risk of maladaptation. Under a rapidly changing climate, however, the traditional guidelines lead toward increasing maladaptation as stands age. An updated paradigm for seed transfer guidelines is an explicit acceptance of proactive transfer in anticipation of future climatic conditions such that there is a calculated initial elevated risk of maladaptation in an attempt to optimize adaptation over the life of the stand.

The projected redistribution of western seed deployment zones by Figure 7B are not as geographically disparate as in eastern Canada. But, the loss of habitat in interior Alaska and along the Mackenzie River corridor down through Alberta could eliminate suitable climatypes before they provide seed for reforestation.

Consequently, there should be a sense of urgency in building a robust seed bank. Movement of genotypes to much colder climates may result in poor seedling survival and suboptimal growth due to frost damage. Rather, we recommend moderate scale transfers among breeding regions that are supported by both appropriate climate differences and population performance from field trials. For example, a transfer from central breeding region D1 northwest into region G2 represents a 1. This transfer also results in slightly better performance of introduced D1 material compared to the local G2 sources Table 3, 1.

Genotypes adapted to warmer region D1 temperatures would be safe to transfer under current climates and additionally be suitable under warming of mean annual temperature by 0. Given the uncertainty of future climate projections, methodological limitations inherent to provenance and progeny testing, and the need for planting stock to survive current climate conditions, assisted migration prescriptions should likely avoid very large transfer distances.

While results from experimental seed transfers in provenance and progeny trials may be among the most valuable information to develop climate change adaptation strategies, the data is not without problems. Genotypes tested in field trials may not have experienced rare climate events such as unseasonal or extreme cold temperatures in the boreal north.

Thus, good growth observed in populations transferred to colder climates may not necessarily reflect their long-term fitness. Another technical limitation of genetic field test is that competition in older trials may exaggerate genetic differentiation of genotypes. We therefore recommend that transfers should generally be moderate approx. Such restrictions could gradually be relaxed to allow for longer distance transfers as the climate continues to warm.

Only the top-performing families should be chosen for assisted migration prescriptions. As an alternative climate adaptation strategy to seed transfer among breeding regions, Table S1 may also be used to remove genotypes from local breeding populations, if their climate sensitivity is indicated by performing poorly when transferred to warmer breeding regions. USFS Assisted migration underway! February news article: Forest Service researchers that the cause was due to climate change.

With climate change, there has been less snow on the ground to insulate the shallow roots from extreme temperatures. And with less snow on the ground, frozen roots have led to the decline of 60 to 70 percent of trees covering , acres in Alaska and British Columbia. Researchers also believe that yellow cedars may thrive in areas outside of where it has already migrated, leading to the hope that assisted migration may restore the dwindling population of these trees.

However, there is also concern that assisted migration may cause yellow cedars to become an invasive species. Nevertheless, a trial planting of yellow cedars in Yakutat has been successful with a first-year survival rate of more than 90 percent. What change in the environment triggered tree death in previously healthy forests? A chronology of the natural his- tory of yellow-cedar helps put forest decline into temporal context.

The location of Pleistocene refugia Carrara et al. An ongoing population-genetics study will address this hypothesis for yellow-cedar. At one location near Petersburg, Alaska, cedar pollen became abundant about years ago Ager et al.

The Little Ice Age c. The ages of mature yellow-cedar trees, whether they are dead or still living, indicate that most of them regenerated and grew to their canopy status in existing forests during the Little Ice Age Hennon and Shaw , Beier et al.

It was during the Little Ice Age that yellow-cedar became more abundant at lower elevations, where it would later be most vulnerable to decline. The onset of yellow-cedar decline coincided with the end of the Little Ice Age Hennon et al. A large pulse of yellow-cedar mortality occurred in the s and s Hennon and Shaw during a notably warm period of the Pacific Decadal Oscillation Mantua A conservation strategy for a climate-sensitive species needs to consider the manner in which past, current, and future climates affect the various ecological traits and life stages of that species.

Because climate changes through time, the adaptive range of species becomes a moving target, and a conservation strategy must be dynamic. Climate is expected to impact each tree species in a unique manner; therefore, there is a need to model each species individually Iverson et al.

Our conceptual approach is to integrate snow cover and drainage in order to identify unsuitable, suitable, and potential new habitats for yellow-cedar. Specifically, we nested soil drainage within favorable climate envelopes, with an emphasis on adequate snow-cover levels, to define habitat suitability as the foundation for a conservation and management strategy for yellow-cedar figure 7.

One species that might substitute for yellow-cedar in the maladapted zone is western red-cedar Thuja plicata [Donn ex D. Don] , which grows in some of the declining yellow-cedar forests at lower elevations in Alaska and British Columbia, south of latitude 57 degrees N. Western redcedar is a calcium-accumulating, decay-resistant, long-lived tree of commercial value that is prized by the local indigenous people. Its bark and wood properties, including wood chemistry, differ from yellow-cedar's, but the two trees have some ecological redundancy and offer similar ecosystem services.

The northern range extent and elevational limit of western redcedar suggest that future warmer climate conditions will favor this tree in Alaska, which also appears to be the case in coastal British Columbia Hamann and Wang More knowledge is needed on redcedar's adaptation to the same freezing injury that afflicts yellow-cedar before intensive efforts of promoting redcedar in declining forests would be justified Schaberg et al. When favorable climate develops beyond its existing range, yellow-cedar may be particularly slow to migrate because of its low reproductive capacity Harris The previously mentioned genetic study is designed to test the Holocene migration of yellow-cedar, which we suspect is slow and still proceeding toward the northeast.

Yellow-cedar is absent from much of the widespread forested wetland in these areas, even though the conditions appear to be favorable for yellow-cedar and may have been so for thousands of years.

Yellow-cedar may benefit from some assistance in migration to speed the colonization of new habitats as the climate warms. Assisted or facilitated migration is the deliberate movement by humans of genotypes and species into areas in which the projected climate is believed to be associated with high probabilities of persistence.

These activities can be controversial, because widespread movements of species can be interpreted as fostering the introduction of invasive species that could bring unanticipated consequences.

Assisted migration may be required for species with narrow resource requirements or poor dispersal ability Warren et al. As a cautious step, we conducted a trial planting of yellow-cedar near Yakutat, Alaska, an area of discontinuous occurrence for yellow-cedar but still within its range limits; Hennon and Trummer to test the survival and growth of yellow-cedar where it did not previously grow.

New USFS technical report: A conservation and management strategy for yellow-cedar in Alaska is presented in the context of climate change. This document has four sections. Section 1 covers the ecology and silvics of yellow-cedar, as well as other background information.

Section 2 outlines knowledge on the extensive mortality to yellow-cedar, including the role of climate. Section 3 describes opportunities for the conservation and active management of yellow-cedar on lands that are considered either suitable or unsuitable for yellow-cedar. Section 4 uses risk models and yellow-cedar distribution data to evaluate, quantify, and map areas of habitat suitability for yellow-cedar, both now and predicted through the year Yellow-cedar at risk of forest decline by the end of the century varies considerably by geography in coastal Alaska.

Some areas are already heavily affected by decline, and risk is not expected to increase appreciably. Other areas are currently unaffected but are expected to develop decline.

Still other areas are expected to remain healthy. This report provides a vulnerability assessment and the scientific foundation for conservation and active management of yellow-cedar on suitable and vulnerable lands.

Specific management considerations are presented regionally and for 33 separate geographic zones where yellow-cedar grows in coastal Alaska. The high genetic variability of yellow-cedar in Alaska shows no evidence of a genetic bottleneck, and is consistent with yellow-cedar occupancy in Alaska throughout the Pleistocene. The ages of mature yellow-cedar trees, whether they are dead or still living, indicate that most regenerated and attained upper canopy status during the Little Ice Age.

We hypothesize that this favorable climate allowed yellow-cedar to regenerate prolifically, even at low elevations, where it would later be most vulnerable to decline.

Therefore, yellow-cedar forests are composed of trees that regenerated and grew during a favorable climate, but have since been subjected throughout portions of the range to a different climate that exposes them to fine-root freezing injury and decline. As a species declines and dies in part of its range, there may be new locations, sometimes called the leading edge, where the climate becomes suitable.

Assisted migration may be necessary for some species of trees that cannot migrate rapidly enough to keep pace with a changing climate. In , a new planting trial was initiated in Yakutat, Alaska, to determine if yellow-cedar could be regenerated and grow in a new, but suitable, environment.

This location was selected because it is farther north and accumulates deep snowpacks over the winter. It is important to note that Yakutat is not outside of yellow-cedar's range because yellow-cedar extends northwest into Prince William Sound.

Third-year survival surveys, conducted in , showed percent survival. Another planting trial, a common garden study, was initiated in to compare yellow-cedar growth rates, foliar terpenes, and freezing resistance. Four different sites, 3 on Prince of Wales Island at a range of elevations and 1 on the mainland at Echo Cove north of Juneau, and 16 different seedlots were included in the study design.

The geographic expression of Yellow-cedar forest mortality is unusual because "Yellow-cedar decline is now known to occur along a north-south axis that covers more than 6 degrees of latitude, or about miles. This mortality is not known to occur furthur south in British Columbia, Washington, Oregon, or California.

Tree species other than yellow-cedar typically do not show elevated mortality rates in stands affected by yellow-cedar decline.

Yellow-cedar decline was known to occur only in older, unmanaged forests until recently, when silviculturist Greg Roberts of the Wrangell Ranger District noticed dying yellow-cedar in young-growth forests on Zarembo Island in southeast Alaska.

He and colleagues assessed this situation initially in the summer of The dying and recently dead yellow-cedars had been previously selected as crop trees in the yr-old precommercially thinned stand. Symptoms of dying trees in the young-growth forest mirrored the classic symptoms of dying mature trees: Also, as is common on nearly dead or recently dead mature trees, the galleries of the bark beetle Phloeosinus and mycelial fans and rhizomorphs of the fungus Armillaria were found on young yellow-cedars in this stand.

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