Abstract  The National Institute for Occupational Safety and Health (NIOSH) has determined that exposure to asbestos fibers causes cancer and asbestosis in humans and recommends that exposures be reduced to the lowest feasible concentration. As the federal agency responsible for conducting research and making recommendations for the prevention of worker injury and illness, NIOSH has undertaken a reappraisal of how to ensure optimal protection of workers from exposure to asbestos fibers and other elongate mineral particles (EMPs). As a first step in this effort, NIOSH convened an internal work group to develop a framework for future scientific research and policy development. This State of the Science and Roadmap for Scientific Research (herein referred to as the Roadmap), clarifies NIOSH's REL, summarizes NIOSH's understanding of occupational exposure and toxicity issues concerning asbestos fibers and other EMPs, and identifies key issues which need to be resolved to allow NIOSH to update its REL. In 1990, NIOSH reviewed the available information on EMPs from the nonasbestiform analogs of the asbestos minerals. The epidemiological evidence was considered inconclusive, and the toxicological evidence was interpreted to mean that carcinogenic potential depends on a mineral particle's length and width and neither chemical composition nor mineralogical origin are critical factors in determining a mineral particle's carcinogenic potential. NIOSH also considered the lack of routine analytical methods to accurately and consistently distinguish between asbestos fibers and nonasbestiform EMPs in air samples. As a result of the review, NIOSH revised its REL at that time, retaining the 0.1 f/cm3 limit but explicitly encompassing EMPs from the nonasbestiform analogs of the asbestos minerals as a precautionary measure. Uncertainty remains concerning the adverse health effects that may be caused by nonasbestiform EMPs encompassed by NIOSH since 1990 in the REL for asbestos, and the Roadmap does not change NIOSH's REL. In the Roadmap, NIOSH makes clear that such nonasbestiform minerals are not "asbestos" or "asbestos minerals," and no longer refers to particles from the nonasbestiform analogs of the asbestos minerals as "asbestos fibers." However, particles that meet the specified dimensional criteria remain countable under the REL for the reasons stated above, even if they are derived from the nonasbestiform analogs of the asbestos minerals. NIOSH's intent is to reduce existing scientific uncertainties, to resolve current policy controversies, and to update its REL. To help accomplish these goals, the Roadmap proposes that interdisciplinary research address the following three strategic goals: (1) develop a broader and clearer understanding of the important determinants of toxicity for EMPs; (2) develop information on occupational exposures to various EMPs and health risks associated with such exposures; and (3) develop improved sampling and analytical methods for asbestos fibers and other EMPs. The results of the research programs are intended to provide a sound scientific foundation for development of future recommendations that provide optimal health protection. Originally published in March 2011, the Roadmap was revised in April 2011 to (1) correct an erroneous statement that NIOSH adopted the designation of asbestos as a "Potential Occupational Carcinogen" § in the 1970s; (2) more clearly indicate that NIOSH has determined that exposure to asbestos fibers causes cancer and asbestosis in humans; and (3) provide an updated discussion of the potency of chrysotile for causing mesothelioma.

Abstract  Heavy sediment loads in the Sumas River of Whatcom County, Washington, increase seasonal turbidity and cause locally acute sedimentation. Most sediment in the Sumas River is derived from a deep-seated landslide of serpentinite that is located on Sumas Mountain and drained by Swift Creek, a tributary to the Sumas River. This mafic sediment contains high amounts of naturally occurring asbestiform chrysotile. A known human-health hazard, asbestiform chrysotile comprises 0.25–37 percent, by mass, of the total suspended sediment sampled from the Sumas River as part of this study, which included part of water year 2011 and all of water years 2012 and 2013. The suspended-sediment load in the Sumas River at South Pass Road, 0.6 kilometers (km) downstream of the confluence with Swift Creek, was 22,000 tonnes (t) in water year 2012 and 49,000 t in water year 2013. The suspended‑sediment load at Telegraph Road, 18.8 km downstream of the Swift Creek confluence, was 22,000 t in water year 2012 and 27,000 t in water year 2013. Although hydrologic conditions during the study were wetter than normal overall, the 2-year flood peak was only modestly exceeded in water years 2011 and 2013; runoff‑driven geomorphic disturbance to the watershed, which might have involved mass wasting from the landslide, seemed unexceptional. In water year 2012, flood peaks were modest, and the annual streamflow was normal. The fact that suspended-sediment loads in water year 2012 were equivalent at sites 0.6 and 18.8 km downstream of the sediment source indicates that the conservation of suspended‑sediment load can occur under normal hydrologic conditions. The substantial decrease in suspended-sediment load in the downstream direction in water year 2013 was attributed to either sedimentation in the intervening river reach, transfer to bedload as an alternate mode of sediment transport, or both. The sediment in the Sumas River is distinct from sediment in most other river systems because of the large percentage of asbestiform chrysotile in suspension. The suspended sediment carried by the Sumas River consists of three major components: (1) a relatively dense, largely non-flocculated material that settles rapidly out of suspension; (2) a lighter component containing relatively high proportions of flocculated material, much of it composed of asbestiform chrysotile; and (3) individual chrysotile fibers that are too small to flocculate or settle out, and remain in suspension as wash load (these fibers are on the order of microns in length and tenths of microns in diameter). Whereas the bulk density of the first (heaviest) component of suspended sediment was between 1.5 and 1.6 grams per cubic centimeter (g/cm3), the bulk density of the flocculated material was an order of magnitude lower (0.16 g/cm3), even after 24 hours of settling. Soon after immersion in water, the fresh chrysotile fibers derived from the Swift Creek landslide seem to flocculate readily into large bundles, or floccules, that exhibit settling velocities characteristic of coarse silts and fine sands (30 and 250 micrometers). In quiescent water within this river system, the floccules settle out quickly, but still leave between 2.4 and 19.5 million chrysotile fibers per liter in the clear overlying water. Consistent with the results from previous laboratory research, the amounts of asbestiform chrysotile in the water column in Swift Creek, as well as in the Sumas River close to and downstream of its confluence with Swift Creek, were determined to be directly correlated with pH. This observation offers a possible alternative to either turbidity or suspended‑sediment concentration as a surrogate for the concentration of fresh asbestiform chrysotile in suspension. Continued movement and associated erosion of the landslide through mass wasting and runoff will maintain large sediment loads in Swift Creek and in the Sumas River for the foreseeable future. Given the present channel morphology of the river system, aggradation (that is, sediment accumulation) in Swift Creek and the Sumas River are also likely to continue.

Abstract  The ATSDR toxicological profile succinctly characterizes the toxicologic and adverse health effects information for the hazardous substance described here. Each peer-reviewed profile identifies and reviews the key literature that describes a hazardous substance's toxicologic properties. Other pertinent literature is also presented, but is described in less detail than the key studies.

Abstract  This document describes the procedures and calculations EPA used to compute the national bioaccumulation factors (BAFs) that were, in turn, used to calculate the Agency’s updated national recommended water quality criteria for human health for 94 chemicals (USEPA 2015). For a scientific discussion of and rationale for using these methods, see EPA’s 2000 Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (2000 Methodology), Technical Support Document Volume 2: Development of National Support Factors (TSD), and EPA’s final 94 criteria documents that describe the development of each chemical-specific bioaccumulation factor included in the 2015 update on the National Recommended Water Quality Criteria – Human Health Criteria Table webpage.