A new report by Environment California Research & Policy Center makes several claims about the health effects of phthalates contained in consumer products that are unsupported by the science. For the past two years, these misleading claims have been the centerpiece of a publicity campaign against the use of phthalates. Following is a point-by-point list explanation of how the misleading claims by the special interest group stack up against the science.
Claim: Phthalates, used in shampoos, perfumes, beauty products, food containers, plastic wrap, children's toys, are among the most frequently found contaminants in human bodies, particularly in women of reproductive age.
Response: The issue is not just whether there is exposure to phthalates, but how those exposures measure against potential effect levels. The average exposures to phthalates measured for humans are far below safety levels set by federal agencies. With respect to women of reproductive age, contrary to an earlier preliminary study, a recent study by the Centers for Disease Control and Prevention (CDC) found that women of reproductive age (i.e., 20 to 39 years of age) had exposures to dibutyl-phthalate (DBP) similar to or even less than adolescent girls and women aged 40 years and older. The DBP exposures for the women of reproductive age are, on average, nearly 90 times lower than the safety level established by the U.S. government. Incidentally, phthalates are not used in food containers or plastic wrap in the U.S.
Claim: Studies have linked phthalates to premature birth.
Response: A recent article published in Environmental Health Perspectives suggests that phthalate exposure is associated with delivery of pre-term newborns. But a review of the data in the study does not support that assumption. DEHP and its metabolites (breakdown products) are quickly cleared from human blood. The presence of DEHP or MEHP in umbilical cord blood in a newborn gives us only a snapshot of exposure on the day of delivery, and tells us nothing about exposures during the course of the pregnancies. Only by tracking a pregnant woman throughout the pregnancy could any conclusions be drawn about exposure to DEHP and its effects on gestational age at delivery. There is no reason to believe that exposure to DEHP on delivery day indicated by this study is representative of a woman's exposure during a pregnancy. Studies show that DEHP exposures vary from day to day and even from one part of the day to another. And substantial data from biomonitoring studies conducted by the Centers for Disease Control and Prevention show that average exposures to the general population are well below safety levels set by the U.S. government.
Claim: Lab studies have also linked phthalates with male reproductive problems, such as undescended testicles and malformed urinary tracts.
Response: No studies have linked phthalates with male reproductive problems in humans. To the contrary, a recent preliminary study on teenagers, who probably had received higher-than-average amounts of the phthalate DEHP when infants, found sex hormone levels and reproductive organ size in males to be normal. Male rats exposed to high levels (far higher than human exposures) of some (but not all) phthalates during their early life do display effects on their reproductive organs, mainly damage to the testes. But a two-year, $1 million study conducted by a Japanese research team found the reproductive health effects in rodents associated with phthalates may not be relevant to humans. The study reveals that the sex organs of male monkeys fed very high doses of di(2-ehtylhexyl) phthalate (DEHP) from weaning to sexual maturity developed normally. In this study, juvenile male marmosets (a type of small monkey and a member, along with humans, of the primate order) that received very high doses of DEHP from weaning to sexual maturity showed no evidence of testicular damage.
Claim: Men with high levels of phthalates or pesticides in their urine (including diazinon, heavily used in California agriculture) tend to have low levels of sperm production.
Response: With respect to phthalates, this claim stems from small, preliminary studies of questionable reliability. A team of researchers has conducted three studies with small groups of men recruited from a fertility clinic to look for any statistical correlations between exposure to various phthalates and different aspects of sperm quality. The results have been inconsistent from one study to another, and inconsistent with existing health effects data on these various phthalates. They are preliminary, small studies, as the authors state, and must be interpreted "cautiously." "The Phthalate Esters Panel takes all such reports seriously," said Marian Stanley, manager of the Panel, "but the results certainly support the authors' admonition not to leap to any conclusions. The studies have a number of built- in shortcomings, which may explain the inconsistent results."
- The subjects tested are not representative of the general population. They were all partners of sub-fertile couples, and thus might be expected to have more sperm-quality problems than a random group of men.
- The results of the testing on the men from subfertile couples were not compared to tests on a randomly selected group of men. That is, there was no control group, a standard methodology in full-fledged epidemiology research. If, for example, the same patterns of phthalate exposure showed up in the random group as in these studies, then the data would have little if any meaning.
- One study showed a statistical association with exposure to DEP (diethyl phthalate), a phthalate that shows very little reproductive biological activity in animal tests. A second study showed correlations with DBP (dibutyl phthalate) and BBP (butyl benzyl phthalate), which do show some reproductive effects in rodents, but at exposure levels that greatly exceeded those detected in the test subjects.. A third study found no associations at all. And no study showed any association with the phthalate that shows the highest activity in rodents.
- Statistical correlations by themselves do not link a cause with an effect. They only raise a possibility that has to be explored by other means.
The levels of phthalates found in the subjects in the three studies were not unusually high. They were consistent with the average exposure levels found in biomonitoring studies conducted by the Centers for Disease Control and Prevention on the U.S. population and far below safety levels set by the U.S. government. The Phthalate Esters Panel of the American Chemistry Council is composed of all major manufacturers and some users of the primary phthalate esters in commerce in the United States.