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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."