This summary table contains detailed information about research studies. Summary tables offer an informative look at the science behind many breast cancer guidelines and recommendations. However, they should be viewed with some caution. In order to read and interpret research tables successfully, it is important to understand some key concepts. Learn how to read a research table.
Introduction: Although it has long been suggested that exposure to environmental pollutants might increase the risk of breast cancer, most studies have not found a link.
Some of the most common and well-studied environmental pollutants are organochlorines. Organochlorines include:
A good way to assess exposure to organochlorines is to measure the levels of these chemicals in a person’s blood. The results of most studies that have measured blood levels of DDE and PCBs, including the Long Island Breast Cancer Study, have found no link between increased levels of these chemicals and breast cancer risk .
Learn more about organochlorines and breast cancer risk.
Learn more about the environment and breast cancer risk.
Learn about the strengths and weaknesses of different types of studies.
See how this risk factor compares with other risk factors for breast cancer.
Read our perspective on pesticides and breast cancer risk (November 2010).*
Read our perspective on cancer cluster studies of pesticides and breast cancer risk (November 2011).*
* Please note, the information provided within Komen Perspectives articles is only current as of the date of posting. Therefore, some information may be out of date at this time.
Study selection criteria: Nested case-control studies with at least 150 breast cancer cases, meta-analyses and pooled analyses. Table note: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk.
Study Population(number of participants)
Relative Risk of Breast Cancer in Women with the Highest Blood Levels of DDE Compared to Those with the Lowest, RR (95% CI)
Relative Risk of Breast Cancerin Women with the Highest Blood Levels of PCBs Compared to Those with the Lowest, RR (95% CI)
Nested case-control studies
Millikan et al. 
Raaschou-Nielsen et al. 
Laden et al. 
Helzlsouer et al. 
Hoyer et al. [6-7]
Krieger et al. 
Ward et al. 
Pooled and meta-analyses
Laden et al. 
Ingber et al. 
11 nested case-control studies
Lopez-Cervantes et al. 
9 nested case-control studies
NS = No statistically significant increase or decrease in risk
† Similarly, when results were examined by hormone receptor status, there was no statistically significant increase or decrease in risk for either hormone receptor-positive or hormone receptor negative breast cancers.
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