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MEMORANDUM

TO: Sandra Gaona

Acting Chief 

Analytical Support Branch 

CC: Daniel Bushman, Ph.D.

Analytical Support Branch

FROM: Jocelyn Hospital

Toxicologist 

Analytical Support Branch 

DATE: November 3, 2014

SUBJECT: Review of National Toxicology Program (NTP) Cancer Classification Data for 1-

bromopropane

The NTP Report on Carcinogens, Thirteenth Edition (RoC) (NTP, 2014) identified 1-

bromopropane as “reasonably anticipated to be a human carcinogen.” The NTP RoC Substance 

Profile for 1-bromopropane (NTP, 2014), the NTP RoC Monograph for 1-bromopropane (NTP, 

2013), the primary NTP study of 1-bromopropane (NTP, 2011), and other supporting documents

cited in the NTP RoC Substance Profile have been reviewed.

Consistent with the EPA Guidelines for Carcinogen Risk Assessment, the NTP RoC 

evaluates the scientific literature and publicly available, peer-reviewed technical reports of 

human and laboratory studies to evaluate whether substances are possible human carcinogens.

The NTP RoC does not present a quantitative assessment of the risks of cancer associated with a 

given chemical. Rather, they indicate the potential hazard associated with chemicals but do not 

establish the exposure conditions that would pose cancer risks to individuals.

Inconsistencies between how the data were interpreted by the NTP and how that same 

data might be interpreted under EPA’s Guidelines for Carcinogen Risk Assessment (U.S. EPA, 

2005) were not identified. The EPA Cancer Guidelines reference the NTP criteria for assessing 

individual studies in the assessment of carcinogenicity, stating “(c)riteria for the technical 

adequacy of animal carcinogenicity studies have been published and should be used as guidance 

to judge the acceptability of individual studies, e.g., NTP, 1984...” (pg. 2-16).

NTP and EPA use similar criteria for listing chemicals as “reasonably anticipated to be a 

human carcinogen” or “likely to be carcinogenic to humans”, respectively. The EPA Guidelines 

for Carcinogen Risk Assessment (U.S. EPA, 2005) specifically detail “likely to be carcinogenic 

to humans” as a comparable weight of evidence term to the NTP classification “reasonably 

anticipated to be a human carcinogen” (pg. 2-53). Supporting data for an agent listed with this 

EPA descriptor includes “an agent that has tested positive in animal experiments in more than 

one species, sex, strain, site, or exposure route, with or without evidence of carcinogenicity in 
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humans”. Based on the available data, the NTP RoC Monograph and Substance Profile have 

identified 1-bromopropane as “reasonably anticipated to be a human carcinogen,” as an 

increased incidence of tumors was observed in experimental animals at multiple sites in multiple 

species.

The conclusions of the NTP RoC for 1-bromopropane were consistent with how the 

Agency would consider the carcinogenicity data available for 1-bromopropane. Therefore, it 

would be appropriate for the Agency, for the purposes of listing 1-bromopropane on the Toxics 

Release Inventory, to conclude that 1-bromopropane can reasonably be anticipated to cause 

cancer in humans. 

References

National Toxicology Program (NTP). (2011). Technical Report on the Toxicology and 

Carcinogenesis Studies of 1-Bromopropane (CAS No. 106-94-5) in F344/N Rats and B6C3F1 

Mice (Inhalation Studies). Toxicity Report Series No. 564. NIH Publication No. 11-5906. 

Department of Health and Human Services, Public Health Service, Research Triangle Park, NC.

NTP. (2013). Report on Carcinogens Monograph on 1-bromopropane. Department of Health and 

Human Services, Public Health Service, Research Triangle Park, NC.

NTP. (2014). Report on Carcinogens, Thirteenth Edition. Department of Health and Human 

Services, Public Health Service, Research Triangle Park, NC.

U.S. EPA. (2005) Guidelines for carcinogen risk assessment. Risk Assessment Forum, 

Washington, DC; EPA/630/P-03/001F.