Overview Asbestos Exposures & Risks WTC-STAC Meeting February 15-16, 2012 WTC Dust Cloud WTC and Post 9/11 Exposures Initial dust cloud estimated to be in excess 100,000 ug/m 3 Initial cloud affected all of southern Manhattan with dispersal of dusts and gases east and southeast of WTC Lioy et al. described 5 specific post 9/11 environmental/occupational exposure categories. Exposed Populations by Category [Lioy, 2006] SnqU' eice of environmental and 1 occupational exposures Cate- gory Time period Predominant for cat eg ories sources of of exposure pollution Pollutants and pollutant classes Primary exposure gronpa 1 First 12 h post- Collapse of Twin Combustion VYTC workers collapse (9/11) Towers products Local employees Burning jet fuel Evaporating gases Local residents Building fires Gaseous, fine, Commuters Resuspended and supercoarse Rescue workers dustand smoke particles Fire and police Federal law en- forcement Press 2 Days 1.5-2 Burning jet fuel Combustion Rescue workers Building fires products Fire and police Resuspended Evaporating gases Federal law en- dustand smoke Gaseous, fine, coarse, and super- coarse particles forcement Local residents Press 3 Days 3-13 Smoldering fires Combustion Recovery workers Resuspended products Construction dustand smoke Gaseous, fine, and workers Local residents Fire and police coarse particles 4 Day 14through Smoldering fires Combustion Recovery workers Dec 29,2001 Debris remov- al bytrucks and equipment products Construction workers Local residents Fire and police 5 Indoors: 9/11 Resuspended Supercoarse Cleanup workers through? dustand smoke particles Somefine and coarse particles Local residents Employees Building visitors Conceptual WTC Outdoor Plume Impacts [Lioy et al. 2005] 1 < gases and very coarse particles Key: Outdoor Exposure Category- # DayG = 9-11-01 #2< gases, very coarse particles, fine particles #4<gases, fine and coarse particles Rain Event Rain Event J #3 <gascs, coarse and fine particles J -H4- 3 -*k- 9 12 Time Post 9-1 1 (Day) 15 18 21 Dust/Fiber Measurement Methods Scanning Transmission Midget Phase Contrast Electron Electron Parameter Imp i tiger Microscopy Microscopy Microscopy Range of Magnification 100 400 2,000-10,000 5.000-20,000 Particles Counted All Fibrous Fibrous Fibrous Structure s b Structure s b Structures 1 ^ Minimum Diameter (size) 1 [UD O.j Jim 0.1 um < 0.01 Mm Visible Resolve Internal Structure No No Maybe Yes Distinguish Mineralogy 4 No No Yes Yes Chrysotile Asbestos in WTC Dusts Chrysotile asbestos constituted 0.8 - 3.0% of mass in settled dusts with most fibers <5 |jm in length. No measurements were made of chrysotile airborne dust concentrations until 9/14, long after the extraordinarily high initial dust cloud. 9400 TEM samples with 22 exceeding the AHERA standard of 70 structures >0.5 |jm long per mm 2 19,000 air samples by PCM, and 4 exceeded the OSHA permissible exposure limit (PEL) of 0.1 f/cm 3 804 breathing zone or general area PCM air samples by NIOSH or contractors detected countable fibers (aspect ratio >3 and length >5 |jm) in 45% of the samples. 25 samples had >0.10 f/cm 3 by PCM but <0.1 f/cm 3 by TEM. Types of Regulated Asbestos Serpentines - Chrysotile Amphiboles - Amosite - Crocidolite - Tremolite - Anthophyllite Asbestos Carcinogenicity IARC 2009: Concluded that exposure to all forms of asbestos (chrysotile, crocidolite, amosite, tremolite, actinolite, and anthophyllite) was associated with an increased risk of lung cancer and mesothelioma. - Sufficient evidence from epidemiological studies that asbestos also caused cancer of the larynx and ovary. - Limited evidence that it caused cancer of the colorectum, pharynx, and stomach. NTP 2011: "Asbestos and all commercial forms of asbestos are known to be human carcinogens based on sufficient evidence of carcinogenicity from studies in humans." Asbestos Quantitative Risk Assessments Human Populations: Retrospective occupational cohorts Measurement Method : PCM measurements of fibers >5 |jm in length. Risk Metric: Cumulative exposures based on the product of PCM concentration and exposure duration (fiber-years). Risk Models: Nearly all assessments use a no- threshold model. No Effect Levels: No scientifically justified threshold for asbestos-related cancers has been established. Limitations of Risk Assessments Limited historical exposure measurement data, resulting in exposure misclassification and likely dampening of the exposure-response. PCM methods measure only a fraction (typically <10%) of the total chrysotile fiber exposure. - Fibers < 0.25 |im in diameter are not detected - Only fibers > 5 |im are counted. Mesotheliomas are not well captured in mortality studies as there was no specific code for mesothelioma until ICD-10 (1999). TEM Airborne Size Distribution Chrysotile in Textiles Only Small Fraction >5 |im in Length Mesothelioma Case-Control Studies Iwatsubo et a/., 1998: France, 405 cases and 387 controls - Odds-ratios increased strongly with cumulative exposure. - Odds-ratio = 4.2 (95% CI=2.0-8.8) for cumulative exposures of 0.5 to 0.99 fiber-years. Rodelspemer et a/., 2001: Germany, 125 cases and 125 controls - Odds-ratios increased strongly with cumulative exposure - Odds-ratio = 7.9 (95% Cl=2. 1-30.0) for cumulative exposures <0.15 fiber-years OSHA PEL is Not Zero Risk OSHA PEL: 0.1 fibers > 5 \im in length per cm 3 as a 8-hour time-weighted-average exposure. OSHA's risk assessment: Exposures to 0.1 f/cc over a working lifetime is associated with an excess risk of 3.4 cancers per 1,000 workers. OHSA Standard Preamble: The 0.1 f/cc level leaves a remaining significant risk."