Phthalates are a family of industrial chemicals known as plasticizers which are used to soften PVC plastic. They are also used as solvents in medications, cosmetics and other consumer products, and have been found to damage the liver, kidneys, lungs, and reproductive system — particularly the developing testes — according to animal studies.

Human studies show widespread population exposure to background levels of phthalates – they seem to be ubiquitous. Recent evidence suggests that particularly high exposure levels may result from orally ingested medicinal products containing phthalates as excipients (inactive ingredients).

They are commonly found in numerous types of modified-release drug delivery systems such as enteric-coated and delayed-release tablets, pelletized delayed-release capsules, or enteric-coated capsules. Phthalates are also used as excipients (fillers) in many drugs. Manufacturers are required to disclose a listing of inactive ingredients in drug product labeling, except when they are used in patented delivery mechanisms where the composition is considered to be a confidential trade secret (U.S. Pharmacopeial Convention 2009). Therefore, one can never know if phthalates are present in a given medication. Ugh!

How does this relate to breast cancer and other hormonally driven cancers? Well, some phthalates mimic estradiol and may promote these types of cancer. Existing epidemiologic studies on this topic are small, mostly not prospective, and have given inconsistent results, but the estrogen-driving effect of phthalates cannot be ignored.

A recent Danish cohort study revealed these associations between phthalate exposures and breast cancer risk, using redeemed prescriptions for phthalate-containing drug products to measure exposure. The results revealed, “High-level dibutyl phthalate (one type of phthalate) exposure (≥ 10,000 cumulative mg) was associated with an approximately two-fold increase in the rate of estrogen receptor-positive breast cancer (hazard ratio, 1.9; 95% CI, 1.1 to 3.5), consistent with in vitro evidence for an estrogenic effect of this compound.”

Every woman might want to think about adding nutritional support that can decrease “bad” estrogens. We suggest our Breast Cancer Prevention Bundle.

Phthalates and Breast Cancer 1