A report released recently by a committee of the National Research Council finds that government risk assessment methods likely underestimate the effects of phthalates, a group of hormone-mimicking compounds widely used in consumer products. Responding to a request from the Environmental Protection Agency (EPA), the committee examined the agency's current approach to assessing health risks of this large family of chemicals. The report concludes that the agency could underestimate phthalate risk if it doesn't consider the effects of combined exposure to different compounds, which can cause more serious or different toxic effects together than they would have caused individually. In other words, the sum could be worse than its parts.
Though unrelated, the report comes in the wake of the newly passed Consumer Product Safety Improvement Act, which bans from certain children's products three types of phthalates permanently and places a temporary ban on three others pending the results of a risk assessment by an expert panel. "Consumers can be exposed to many different phthalate compounds, so we hope this new panel will follow the report's recommendations and assess the cumulative effects of these compounds‚" says Carolyn Cairns, Program Leader for Product Safety at Consumer Reports.
Because they can upset the delicate balance of hormones, phthalate exposure during key periods of fetal development has been linked, mostly in animal studies, to a host of problems in the developing fetus. The male reproductive system is particularly at risk since phthalates interfere with androgens—male hormones like testosterone—causing defects in the position of the urethra (hypospadias is the scientific term), testicular development and fertility. Some phthalates have also been linked to liver cancer.
Phthalate compounds with different chemical structures can interfere with androgen activity in ways that are different, yet lead to the same health outcome. The report stresses that particularly for hormone-mediated effects, risk assessments should group chemicals by common outcome, regardless of the chemical structure or mechanism involved. That will mean assessing products that may contain multiple phthalates or multiple products that may be used together or frequently in ways that could compound an individual's total phthalate intake. Surprisingly, one such product may be certain types of medications.
Phthalates in medication
Researchers from Harvard, Boston University, and the Centers for Disease Control and Prevention recently published a new study that found high phthalate metabolites in people taking certain medications.
The study identified some 47 different drugs that may contain phthalates used to make coatings for some drugs. The study analyzed urine samples from a group of nearly 8,000 people, testing for metabolites of several common phthalates, including dibutyl phthalate, one of several banned in Europe and in some U.S. products. Metabolite levels were significantly higher in people who reported taking at least one of four different phthalate-containing medications: mesalamine (a colitis treatment), didanosine (for HIV), omeprazole (an ulcer treatment), and theophylline (for asthma and lung disease).
Based on levels detected in the urine, researchers estimate that exposures in some people may exceed safety thresholds that the Environmental Protection Agency established for some phthalate compounds. The findings raise new concerns about the safety of inactive ingredients in these and other prescription and over-the-counter medications, particularly those used by pregnant women and children who may be particularly vulnerable to reproductive and developmental toxins.