Environment and Breast Cancer: Science Review

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magnetic fields

Cancer studies: Mammary gland tumors
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Originating list
The list(s) or database(s) in which the chemical was identified as showing an increase in mammary gland tumors. CPDB: Carcinogenic Potency Database, IARC: International Agency for Research on Chemicals Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Man summaries, NTP TR: National Toxicology Program (NTP) Technical Reports, NTP 11ROC: NTP 11th Report on Carcinogens, CCRIS: Chemical Carcinogenesis Research Information Service.
IARC Monographs
Mammary gland tumor summary
A summary of findings related to mammary gland tumors, most often excerpted from IARC Monographs or the NTP 11th ROC, and, in some cases, supplemented by our evaluation of individual studies and reviews, is available for the priority chemicals and 67 others.
Very weak evidence. Some studies may show promotion effect. An NTP study of magnetic fields did not find mammary gland tumors.
Only review sources are listed for this chemical because of lower likelihood of exposure.
Source Type
International Agency for Research on Cancer, Monographs on the evaluation of carcinogenic risk of chemicals to man.VOL.: 80 (2000) Static and Extremely Low-Frequency (ELF) Electric and Magnetic Fields, Magnetic Fields (ELF), Electric Fields (ELF), Electric Fields (Static), Magnetic Fields (Static). Summary of Data Reported and Evaluation.
Two multistage carcinogenesis studies combining exposure to N-methyl-N-nitrosourea with exposure to static or 50-Hz magnetic fields were performed in the same laboratory using an uncharacterized outbred rat strain. The first study demonstrated an increase in mammary tumor incidence with exposure to the fields regardless of exposure to N-methyl-N-nitrosourea. Eleven multistage carcinogenesis studies combining exposure to 7,12-dimethylbenz[a]anthracene with exposure to 50- or 60-Hz magnetic fields were performed in three different laboratories. One laboratory performed six 13-week studies and one 27-week study aimed at addressing exposure-response relationships for different magnitudes of exposure to magnetic fields. These studies reported significant increases in mammary tumor incidence at higher exposure levels. A pooled analysis of exposure response from these studies yielded an average slope significantly different from zero. A second laboratory conducted three studies (two of which were considered inadequate to assess tumour incidence) to replicate these findings at the highest field strengths, but saw no enhancement of mammary tumorigenesis by exposure to ELF magnetic fields in one study, in which the sham control incidence was low enough to detect an increase. In the two other studies, high incidences of mammary tumors in sham controls limited comparisons to possible increases in tumour multiplicity; none were found. The third laboratory studied the impact of intermittent exposure to magnetic fields and saw no changes in tumor incidence or tumor multiplicity in either of two experiments.
National Toxicology Program Technical Report 489, 1999
Primary Literature
National Toxicology Program Technical Report 488, 1999
Primary Literature
National Toxicology Program 11th Report on Carcinogens, Table 1. Chemicals nominated to the National Toxicology Program for in-depth toxicological evaluation for carcinogenesis testing in fiscal years 1988-2003.
Nominated by Electric Power Research Institute in 1989. Rationale: Recent epidemiological studies weakly support an association between exposure to magnetic fields and the incidence of cancer in both residential and occupational environments; Data from carcinogenicity studies needed to resolve public health concerns about the possible effects of electric and magnetic fields on human health Current NTP Status: http://ntp-server.niehs.nih.gov/htdocs/Results_Status/Resstatm/M90023.Html