Phthalates are among the most thoroughly studied families of compounds in the world. Because of this, it is not unusual for new studies to be reported every week. And, while some of these studies have suggested a link between phthalates and various human health effects, none has demonstrated an actual causal link (that phthalates are the cause of the effect). Because phthalates are found in many consumer products, most people are exposed to phthalates every day, but phthalates don’t migrate out of products easily and they don’t accumulate in our bodies. In fact, they begin to breakdown within minutes and are metabolized within 12 to 24 hours.
Below are answers to some common questions based on what you may have heard or read about phthalates and human health effects. Importantly, no single epidemiological study— the study of the distribution and determinants of health-related states or events in specified populations—can prove an actual cause-and-effect link. That’s why the authors of these studies caution against drawing conclusions, and advise on the essential need to replicate the results. It is important, therefore, to keep these cautions in mind when reading about these studies.
Q. Do phthalates cause allergic reactions?
A. Testing has not shown phthalates to be allergens, nor has testing shown them to be strong irritants, so allergy science tells us that it is unlikely that they could act as triggers for allergic reactions.
Q. Is there any scientific evidence linking phthalates to autism?
A. There are no studies that have demonstrated that phthalates cause autism. One study by Swedish and U.S. researchers looked at the association between indoor environmental factors and autism and found the results “far from conclusive.” Importantly, the study did not track, measure or record any exposure to phthalates. The authors cautioned their conclusions were “puzzling, even baffling, and not readily explicable at this time” and that “further and more extensive exploration” is needed.
Q. Is there any scientific evidence linking phthalates to obesity?
A. No studies have found exposure to phthalates to cause obesity in humans. For example, one study by Teitelbaum et al. that looked into childhood obesity makes no claim that exposure to phthalates causes an increase in weight. The authors report only a very preliminary statistical correlation between weight and phthalate exposure, and note further study is required. Moreover, we are not aware of any scientific evidence from decades of animal studies that links any phthalate to an increase in weight.
Q. Is there any scientific evidence linking phthalates to bone disease?
A. Decades of long-term animal studies show no connection between phthalate exposure and skeletal problems. A study of phthalate effect on animal osteoblasts by Sabbieti et al. exposed mouse and rat bone cells in culture dishes to full, intact phthalate molecules. However, what the researchers did to the bone cells is not what happens in living things—living organisms exposed to phthalates almost immediately break them up into smaller molecules that behave in a very different way. Thus, exposing cells in a dish to the whole molecule isn’t relevant to the way humans are actually exposed to phthalates in the real world.
Q. Do phthalates affect newborns’ birth weight?
A. Phthalates have not been shown to cause any birth weight abnormalities in infants. One study by Zhang et al. in China reports low birth weight in infants statistically correlated with phthalate exposure at birth. However, the authors of the Chinese study are cautious about their conclusions and note the limitations of the study. Other studies, including one by Wolff et al. (2009) in Environmental Health Perspectives (EHP) and another published in Human and Ecological Risk Assessment, report no change in birth weight or other outcomes associated with phthalate exposure even though phthalate levels were unusually high.
Q. Do phthalates affect infants’ neurological development?
A. Previous animal tests involving very high doses of phthalates show no neurological effects in females or males. A 2009 study by Engel et al. claims that prenatal exposure to phthalates reduces newborn girls’ alertness. However, the study also found that the infant males showed no decline in alertness, and even a small increase in "motor performance,” indicating that phthalates have beneficial rather than detrimental effects on infants’ neurological development. The conflicting results suggest that the study is inconclusive, especially as the authors note that there is no known mechanism to explain the reported effect.
A recent report suggesting an association between phthalate exposure and attention deficit/ hyperactivity disorder (ADHD) is based on observations of symptoms, not on a clinical diagnosis of ADHD, and on a single measurement of phthalate metabolites in urine which provides no information on long term exposure levels.