Update of NIOSH Carcinogen Classification 

and Target Risk Level Policy for

Chemical Hazards in the Workplace

NIOSH Carcinogen Policy

Paul A. Schulte, PhD

Director, Education and Information Division

Public Meeting, December 16, 2013

1
Why Update the Carcinogen Policy?

 New scientific advances in risk modeling, 

biological mode of action, and analytical methods

 Receive peer and public input on the NIOSH 

process

 Increase the transparency of the NIOSH process

2
Current Intelligence Bulletin

 Carcinogen classification

 Target risk level for carcinogen RELs

 Analytical feasibility and engineering 

achievability

3
Carcinogen Classification: History

 Since 1978 NIOSH used “potential occupational 

carcinogen” as its highest designation

 Some dissatisfaction with that terminology

 Known carcinogens such as asbestos, benzene, and 

cadmium were mislabeled

 NIOSH requested public input in 2011

 Public meeting on issues in December 2011

 Currently: draft document on web for public/peer 

review 

 http://www.cdc.gov/niosh/docket/review/docket240A/pdf/EIDCIB-11052013.pdf

4
Carcinogen Classification: Features

 Utilizes NTP, EPA, and IARC cancer classifications 

for chemicals

 Evaluates occupational relevance in terms of 

exposure and applicability of the data

 Assigns Globally Harmonized System (GHS) 

category for hazard communication

5
Occupational Relevance of

Carcinogen Classification

 Potential for worker exposure

 Applicability of evidence to occupational 

carcinogenicity

 Mode of action

 Route of exposure

6
NIOSH Chemical Carcinogen Review Process

7
Correspondence of Carcinogen Classification 

with GHS Carcinogen Categories*

NTP RoC IARC EPA 1986 EPA 2005 GHS Category/

Hazard Phrase

Known to be a 

human 

carcinogen

Group 1

Carcinogenic to 

humans

Group A

Human 

carcinogen

Carcinogenic 

to humans

Category 1A

Known human 

carcinogen

Reasonably

anticipated to 

be a human 

carcinogen

Group 2A

Probably carcinogenic 

to humans

Group B1

Probable human 

carcinogen

Likely to be 

carcinogenic 

to humans

Category 1B

Presumed 

human 

carcinogen Group 2B

Possibly carcinogenic 

to humans

–adequate in animals; 

inadequate in humans

Group B2

Probable human 

carcinogen

Group 2B

Possibly carcinogenic 

to humans

–limited animal 

evidence

Group C

Possible human 

carcinogen

Suggestive 

evidence of 

carcinogenic

potential

Category 2

Suspected 

carcinogen

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*As interpreted by NIOSH
Carcinogen Classification

Sample Determination: Benzene

 NIOSH occupational carcinogen

 GHS carcinogen category 1A: known human 

carcinogen

 Based on: 

 NTP: known to be carcinogenic to humans

 EPA: Group A: human carcinogen

 IARC: Group 1: carcinogenic to humans

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Carcinogen Classification

Sample Determination: Heptachlor

 NIOSH occupational carcinogen

 GHS carcinogen category 1B: presumed human 

carcinogen

 Based on: 

 EPA: Group B2-probable human carcinogen (sufficient 

data in animals)

 IARC: Group 2B-possibly carcinogenic to humans 

(sufficient data in animals)

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Target Risk Level for Carcinogen RELs: 

History

 Prior to 1995: lowest feasible concentration

 Determined by employers

 Employer evaluated technical and economic options

 In 1995: adopted a quantitative basis for RELs

 Based on quantitative risk evaluation

• Use mathematic models to evaluate exposure-response relationships

• Extrapolate from animals to humans and from high doses to low 

doses

 Acknowledged residual risks

 Inherent in establishing an REL is a target risk level but no such 

level was specified

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Risk Levels in New NIOSH Carcinogen Policy

 NIOSH affirms scientific knowledge that the only 

way to eliminate excess risk from carcinogens is 

to prevent exposure

 NIOSH advocates using safer alternatives and to 

substitute noncarcinogen chemicals whenever 

feasible

 Removing all carcinogens in commerce is 

impractical so guidance on reducing carcinogen 

exposures to workers is needed

 NIOSH will assess risks using quantitative 

methods when data are available

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Risk Levels in New NIOSH Carcinogen Policy

 Communicate an array of lifetime cancer risk for 

exposures from 1/100 to 1/1,000,000

 Provides useful information to employers and workers 

to take preventive action

 NIOSH will identify a minimum level of protection 

– this is 1 in 1000 risk level; to establish a REL a 

target risk level is needed

 NIOSH advocates trying to achieve exposures 

resulting in risks lower than 1 in 1000

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Basis for Target Risk Level

 U.S. Supreme Court “Benzene Decision” 

characterized a range of risks between 1 in 1000 

and 1 in a billion

 Implied that 1 in 1000 was a significant risk

 NIOSH will use the 1 in 1000 target risk level 

because it better relates to OSHA’s work in 

developing occupational exposure limits

 NIOSH will use mathematic models for 

quantitative risk assessment

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NIOSH Precedent for Using 1 in 1000 Risk Level*

1990

1990

1991

1995

1998 

2001

2002

*

Includes health effects other than cancer

Benzene PEL (Testimony to OSHA)

Cadmium PEL (Testimony to OSHA)

1, 3-Butadiene PEL (Testimony to OSHA)

Coal dust (REL)*

Diesel exhaust (Journal article/collaboration 

with MSHA)*

Silica (Journal article-risk assessment)

Silica (Journal article-risk assessment) *

15
NIOSH Precedent for Using 1 in 1000 Risk Level 

(cont’d)*

2007

2011

2013

2013

*

Includes health effects other than cancer

Manganese (Journal article-risk assessment)

*

Titanium dioxide (RELs)

Hexavalent chromium (REL)

Diacetyl/2,3-Pentanedione (Draft REL)*

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Additional Protections Afforded by Risk 

Assessment and Related Communications

 Use of 45-year working lifetime

 Treats exposure-response as linear at low doses

 Default assumption

 In some cases sufficient mode of action data may allow 

risk estimation based on non-linear dose-response 

models

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Low Dose Extrapolation

Risk

Exposure

Linear

Sub-linear

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Additional Protections Afforded by Risk 

Assessment and Related Communications

 NIOSH REL will be based on 95% lower 

confidence limit of the exposure corresponding 

to the target level of risk

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Confidence Interval

Risk

Exposure

95% confidence 

limit on exposure

20
Additional Protections Afforded by Risk 

Assessment and Related Communications (cont’d)

 NIOSH guidance is that risks should be kept well 

below the REL. Lower exposure lowers the risk.

 NIOSH recommends alternatives when possible

 For these reasons the actual risk on which a REL is 

based will be less than 1/1000

21
Analytical Feasibility and

Engineering Achievability: History

 “. . . Engineering controls . . . should be used to 

control occupational exposures to the fullest 

extent feasible.” [1988]

 “NIOSH RELs will be based upon risk evaluations . 

. . and on an assessment of what levels can be 

feasibly achieved by engineering controls and 

measured by analytical techniques.” [1995]

22
Analytical Feasibility and

Engineering Achievability: Issues

 Not all NIOSH RELs are health-based

 Many NIOSH RELs are based on analytical 

feasibility

 NIOSH has made some evaluations of 

engineering feasibility or achievability, but has 

not routinely conducted quantitative analyses of 

the technical feasibility of achieving RELs

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Analytical Feasibility and

Engineering Achievability

 NIOSH will no longer establish carcinogen RELs 

relying on an evaluation of engineering controls, 

but will make an effort to provide control 

information

 Basis of NIOSH RELs

 Health effects (quantitative risk assessment)

 Analytical feasibility (measurement of chemical in the 

work environment)

24
Analytical Feasibility and Engineering 

Achievability: New RELs Policy

 For new RELs, NIOSH will distinguish between 

health-based and analytical feasibility-based RELs

 Health-based RELs = REL

 RELs based on analytical feasibility = RELAF

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Timeline

 Public meeting (December 16, 2013)

 Receive all public comments by February 13, 2014

 Receive all peer review comments by March 14, 

2014

 Anticipate completion of FINAL Cancer Policy in 

2014

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Carcinogen and RELs Policy Update Committee

 David Dankovic (EID)

 John Decker (OD)

 Charles Geraci (EID)

 Pius Joseph (HELD)

 Eileen Kuempel (EID)

 Thomas J. Lentz (EID)

 Qiang Ma (HELD)

 Kathleen MacMahon (EID)

 Lauralynn McKernan (EID)

 Paul Middendorf (OD)

 Rick Niemeier (ret.)

 Andrea Okun (OD)

 Faye Rice (EID)

 Teresa Schnorr (DSHEFS)

 Paul Schulte (EID)

 Christine Sofge (EID)

 Patricia Sullivan (DRDS)

 Mark Toraason (OD)

 Ainsley Weston (DRDS)

 Ralph Zumwalde (EID)

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Thank you!

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For updates visit the NIOSH Carcinogen Policy web page:

http://www.cdc.gov/niosh/topics/cancer/policy.html