Phthalates exposure may double breast cancer risk ... or not

Mar 19, 2010

López-Carrillo, L, RU Hernández-Ramírez, AM Calafat, L Torres-Sánchez, M Galván-Portillo, LL Needham, R Ruiz-Ramos and ME Cebrián. 2010. Exposure to phthalates and breast cancer risk in northern Mexico. Environmental Health Perspectives.

Women with higher exposure to additives used in some personal care and food products may have an increased risk of breast cancer.

Researchers conducting a study of phthalate exposure and breast cancer among Mexican women reported that metabolites of one type of phthalate are associated with at least twice the risk of breast cancer, while other types appear to lower risk.

Exposure to phthalates has been associated with a number of adverse health outcomes in humans, and particularly in men.  Few studies have, however, investigated the health effects of these widely used chemicals in women. This is the first human study to evaluate associations between exposure to phthalates and breast cancer. 

Exposure to these chemicals is ubiquitous as demonstrated by the large percentage of the U.S. population found to have detectable levels of phthalate residues in their urine. Phthalates act as stabilizers, lubricants and binding materials. They are found in a variety of products including vinyl, cosmetics, pharmaceuticals, medical devices, children's toys and detergents.

After taking into account the known risk factors for breast cancer and exposure to other phthalates, researchers found that the concentration of one type of phthalate residue – monoethyl phthalate (MEP) – in urine was associated with an increased risk of breast cancer. The association was even stronger when they limited their analysis to premenopausal women.

The concentration of the phthalate residues MEP and monoethyl carboxylpentyl phthalate (MECPP) were respectively 60 percent and 10 percent higher in women with breast cancer relative to controls. After adjusting for other risk factors, women in the highest third of exposure to MEP had twice the risk of breast cancer relative to women in the lowest third. Among premenopausal women, those with high exposure had a 4-fold increased risk of breast cancer.

While higher exposure to MECPP was associated with a 68 percent increased risk of breast cancer, women with higher levels of other phthalate residues, such as monobenzyl phthalate (MBzP) and monocarboxypropyl phthalate (MCPP), had an about 2-fold lowered risk of the disease.

These findings were obtained after measuring the urine concentration of nine phthalate residues in 233 women with breast cancer and 221 healthy controls matched on age and residence location. Information was collected on known risk factors for breast cancer. Urine samples were collected and analyzed for urinary metabolites of phthalates.

Because this is the first study to compare phthalate exposure and breast cancer risk, findings must be interpreted with caution and more studies are needed to confirm the results. As for all scientific research, this study has limitations. For instance, although the measurement of phthalates in urine is a common method to estimate exposure, these chemicals are rapidly eliminated from the body and a single measurement may not reflect exposure before tumors developed.  It is also possible that women with breast cancer eliminated phthalates at a different rate from healthy women.