Evaluating Worker Risks to TCE

The Status of TCE Occupational Exposure Limits

The Importance of Informed Substitution

EPA TCE Workshop 

July 29, 2014

Julia Quint, PhD

CA Dept. of Public Health 

(Retired)

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Presentation Overview

► Evaluating Worker TCE Health Hazards / Risks 

Basis of TCE Occupational Exposure Limits 

► Protecting CA Workers from Chemical Hazards

“Early Warnings” and Risk-Based PELs

► Challenges in Evaluating Worker TCE Health 

Risks

► Identifying Safer Substitutes for TCE 

► Case Studies of Regrettable TCE Substitutes

n-Hexane and 1-Bromopropane 
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Why QRA is Used to Develop PELs

Benzene Court Decision 

(1980)

OSHA responsible for 

demonstrating significance 

of risk when developing 

PELs

Significant cancer risk is 

between 1/billion and 

1/1000 (Judge)

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Selected OSHA Cancer Risk Estimates

(Excess Cancers per 1,000 Workers)

Federal Register V. 71, No. 39, 2006

Standard Risk at Prior 

PEL

Risk at New PEL Date

Ethylene oxide 63-109 1.2-2.3 1984

Asbestos 64 6.7 1986

Benzene 95 10 1987

Formaldehyde 0.43-18.9* 0.0056-2.64* 1987

Methylenedianiline6-30** 0.8 1992

Cadmium 58-157 3-15 1992

1,3-Butadiene 11.2-59.4 1.3-8.1 1996

Methylene Cl 126 3.6 1997

Chromium VI 101-351 10-45 2006

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*Range is based on maximum likelihood estimate (0.43, 0.0056) and upper 

95% confidence limit (18.9, 2.64). **Estimated exposure, no prior standard.
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1997 Cal OSHA Airborne Contaminants Advisory 

Committee ―PEL Recommendations

• Acetaldehyde

• Carbon tetrachloride

• Cobalt, elemental and 

inorganic compounds, as 

Co

• Cr VI compounds

• p-Dichlorobenzene

• 1,1 –Dimethylhydrazine

• Glass, fibrous

• Heptachlor

• Hexachlorobenzene

• Hydrazine

• Perchloroethylene

• Phenyl glycidyl ether

• Trichloroethylene

• Vinyl acetate

• 4-Vinyl cyclohexene

• Vinyl cyclohexene dioxide
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The Cal OSHA Airborne Contaminants 

Advisory Committee 

Carcinogen Position Statement (1997)

These substances have been identified by IARC as a carcinogen (Group 2B 

or higher). 

The recommended exposure limits are based on other types of toxic 

results, damage or interference with organ systems, irritation, respiratory 

problems, etc. 

Quantitative risk assessments can be used to estimate risks of cancer at 

various exposure levels in order to set a PEL. 

No such risk assessments have been conducted by this committee. 

Neither Cal OSHA nor the Occupational Safety and Health Standards 

Board have standard methods for performing these assessments or a 

useful criterion against which limits might be set.

Cal OSHA should reconsider the proposed PELs if a carcinogen guideline 

policy is adopted & appropriate resources allocated.
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Identifying Chemical Hazards and 

Evaluating Risks to CA Workers

Hazard Evaluation System & Information Service 

(HESIS), Occupational Health Branch, CDPH

Established by CA Legislature in 1979 

Identify and evaluate workplace chemical hazards

Translate “toxicology” into practical language

Issue “early warnings” on new/unrecognized hazards

Recommend protective standards to Cal/OSHA
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Cal/EPA’s Office of Environmental Health 

Hazard Assessment (OEHHA)

Mission

Protect & enhance public health 

& the environment by scientific 

evaluation of risks posed by 

hazardous substances

Vision

To be California’s leading 

scientific organization for 

evaluating risks to human & 

ecological health

Relevant Functions

Develop and recommend to the 

Air Resources Board healthprotective exposure levels for toxic 

air contaminants

List chemicals known to the state 

to cause cancer or reproductive 

harm to implement Proposition 65

Staff Resources (2005) 

64 PhDs

7 Physicians

21 Masters in public health science
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Occupational Health Hazard Risk 

Assessment Project for California

HESIS’ project concept and contract with OEHHA:

Conduct a systematic analysis of whether existing QRA 

data could be used to develop protective PELs

Screen Proposition 65 List for workplace chemicals of 

concern (unregulated or under-regulated chemicals)

Describe and apply methods for calculating health 

protective air concentrations

Discuss scientific issues related to dose-response 

assessment for the occupational setting
CA Occupational Health Hazard Risk 

Assessment Project – Some Key Findings

44 workplace chemicals listed as “known to cause 

cancer”* did not have PELs

5 chemicals listed as “known to cause 

reproductive/developmental toxicity”* did not 

have PELs

62 Prop 65-listed carcinogens had PELs that were 

not based on cancer (no QRAs conducted)

14 Prop 65-listed reproductive/developmental 

toxicants had PELs that were not explicitly based 

on this endpoint, or the PEL bases were unclear

*Prop 65 List=12/2006. Final Project Report=12/2007 

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CA Occupational Health Hazard Risk 

Assessment Project –Findings/Conclusions

Adjusted OEHHA & EPA QRAs can be applied 

to the workplace, which leverages resources

Using existing QRAs to develop OELs requires 

appropriate expertise

Lifetime cancer risks at existing PELs are high for 

many workplace chemicals

Science-based OELs can be developed using a 

transparent & risk-based approach 

Risk managers can still take technical & 

economic feasibility into account to set limits

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CA Occupational Health Hazard Risk 

Assessment Project – High Cancer Risks

Chemical PEL Basis Cal/OSHA

Risk at PEL*

OSHA 

Risk at PEL*

Acetaldehyde Irritation 24 210

Naphthalene Irritation; blood 

effects

310 310

Perchloroethylene CNS impairment 200 744

Trichloroethylene CNS impairment; 

renal toxicity

53 196

Ethylbenzene Irritation; CNS 

impairment

210 210

1,4-Dioxane Liver damage 135 558

p-Dichlorobenzene Kidney damage 129 959

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*Cancer risks/1000 workers calculated using OEHHA unit risk values adjusted for 

occupational exposure [10 m3/20 m3 x 250 days/365 days x 40 years/70 years]
Cal/OSHA QRA-Based PELs−Examples

Chemical Prior PEL QRA-Based PEL Cancer 

Risk/Health 

Endpoint

1,4-Dioxane 25 ppm 0.28 ppm 1.4/1000

Cyclonite (RDX) 0.5 mg/m3 0.075 mg/m3 Liver damage

1-Bromopropane None 5 ppm Reproductive & 

Developmental

NMethylpyrrolidoneNone 1 ppm Developmental

Toluene 50 ppm 10 ppm Developmental

Ethylbenzene 100 ppm 5 ppm 10/1000

Methyl-n-butyl

ketone

5 ppm 1 ppm Peripheral

Neuropathy

Sulfuric acid 1 mg/m3 0.1 mg/m3

Carcinogen Designation

Pulmonary 

function

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Evaluating Worker Chemical Risks—

Some of the Challenges

Large # of chemicals / limited toxicity & QRA data

Limited toxicology resources in OSHA and other 

occupational health agencies/programs

Exposure and use information lacking—chemical 

prioritization is difficult

Numerous, competing worker protection obligations 

(infectious disease, heat, ergonomics, safety, etc.) 

Limited participation of key stakeholders (small 

employer and worker representatives

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Informed Substitution of TCE and Other 

Toxic Chemicals— Some General Guidelines

Safer chemical substitution—old concept, but 

often not specific regarding recommendations

Effective substitutes must address functional uses

Evaluating health and environmental hazards of 

substitutes prevents transfer of risks (use lists, 

searches, etc.). Avoid “no data” substitutes

Identify substitutes with demonstrated efficacy

Anticipate and address (if possible) other known 

toxic chemicals that may be used as substitutes 

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Regrettable TCE Substitute−

n-Hexane 

TCE, methylene chloride, and 

perchloroethylene in vehicle 

repair cleaners were banned by 

CA Air Resources Board(CARB)

n-Hexane put in auto cleaners as 

a substitute solvent 

Workers developed peripheral 

neuropathy

Condition diagnosed by an 

occupational medicine physician
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HESIS Response to n-Hexane Illnesses 
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Safer Auto Repair Aerosol Cleaners

Two-year EPA Pollution Prevention Grant

Collaboration with the Institute for 

Research & Technical Assistance (IRTA)

IRTA developed & demonstrated the 

effectiveness of safer aerosol automotive 

cleaners

Promoted use of safer aerosol cleaners

Promoted use of integrated illness, injury & 

P2 strategies in the industry
Regrettable TCE Substitute−

1-Bromopropane (Background)

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HESIS Hazard Alert (2003)

DBCP structural analog

Replaced ozone-depleting 

solvents

NTP CERHR Report

Male, female reproductive 

toxicant & developmental 

toxicant (animals)

Nerve damage (workers)

Cancer (animal bioassay in 

progress in 2003, later positive) 
1-Bromopropane Use in Vapor Degreasing−

Case Report of Peripheral Neuropathy (2009)

Machinist at microwave equipment 

firm worked daily with Lenium ES 

(80-90% 1-bromopropane)

Bilateral heel pain for 4 months 

Initially diagnosed with plantar 

fasciitis

Neurologist later diagnosed 

peripheral neuropathy

Worker found the HESIS 1-BP Alert 

on internet and recognized product

Medical Examiner concluded more 

probable than not caused by 1-BP

HESIS reported case to NIOSH

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Some Ways to Prevent Adverse Effects on 

Workers’ Health From Regrettable Substitutions

Require toxicity testing before marketing new chemicals 

and implement restrictions, as needed, to help ensure 

their safe use

Support/ensure the development of safer alternatives for 

specific uses of toxic chemicals that are demonstrated to 

be efficacious and cost-effective before restricting 

chemical use

Identify and specify chemicals that cannot be used as 

substitutes for restricted toxic chemicals

Integrate and coordinate strategies to protect health and 

the environment from toxic chemicals

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