Scientific research into health effects of chemical exposures from food packaging and plastics may have taken 2 steps forward and 1 step back this week.
Two research articles published online August 19 in Pediatrics add to evidence that bisphenol A (BPA) and phthalates may be associated with increased health risks for children and adolescents, but an accompanying commentary casts doubt on the articles because of the measure of exposure used in the studies.
BPA and BMI
In the article on BPA exposure, Donna S. Eng, MD, from the Division of Pediatric Endocrinology, University of Michigan School of Public Health, Ann Arbor, and colleagues analyzed data from the National Health and Nutrition Examination Survey 2003-2010 to assess associations between urinary BPA and obesity and chronic disease risk factors.
They found that higher levels of urinary BPA in children and adolescents aged 6 to 18 years were associated with higher odds of obesity and abnormal waist circumference-to-height (WC-to-height) ratio but did not find significant associations between BPA levels and other chronic disease risk factors.
Of 10,990 children in the survey, 3370 had both body mass index (BMI) and BPA data recorded. When the researchers categorized BPA levels into quartiles and performed logistic regression analysis, they found an increase in the odds of obesity with increasing quartiles of BPA, with those in the highest-concentration quartile having twice the risk as those in the lowest-concentration quartile (odds ratio [OR], 2.01; 95% confidence interval [CI], 1.36 - 2.98; P = .001). They found a similar association for increased odds of abnormal WC-to-height ratio between the highest and the lowest quartiles (OR, 1.55; 95% CI, 1.12 - 2.15; P = .01).
"Our work provides additional evidence of an association between BPA and excess levels of body fat in children, as measured by BMI and WC-to-height ratio," the researchers write. The results are similar to other studies in the United States and China that have linked higher urinary BPA levels to higher odds of obesity in adults, they write, although reverse causation cannot be ruled out. "It is possible obese individuals store BPA differently than nonobese individuals, thus leading to higher concentrations of BPA in the urine."
Phthalates and Insulin Resistance
In the article on phthalate exposure, Leonardo Trasande, MD, from the Department of Pediatrics and the Department of Environmental Medicine, New York University School of Medicine, New York City, and colleagues analyzed National Health and Nutrition Examination Survey 2003-2008 data for 766 fasting 12- to 19-year-olds for associations between urinary phthalate, particularly di-2-ethylhexylphthalate, and insulin resistance.
After dividing urinary phthalate levels into tertiles, the researchers found adolescents in the lowest tertile had a 14.5% prevalence of insulin resistance compared with adolescents in the highest tertile who had a 21.6% prevalence of insulin resistance (95% CI, 17.2% - 26.0%; P = .02).
The authors note that this is the first study to examine an association between an environmental chemical and insulin resistance. "We have identified a cross-sectional association of [di-2-ethylhexylphthalate] metabolite exposure with increased insulin resistance in a large sample of US children," they write.
The researchers caution, however, that "causation cannot be inferred," and it is possible that "insulin-resistant children have unhealthy eating behaviors, including more packaged food consumption, and thus have higher urinary levels."
In an accompanying commentary, Robert L. Brent, MD, PhD, DSc, from the Alfred I. DuPont Hospital for Children, Thomas Jefferson University, Wilmington, Delaware, cites multiple studies that have produced conflicting results for BPA and criticizes both studies for using urinary content of the chemicals as surrogates for chemical exposure.
"Both of the studies published in this issue combined with the others that I have referenced in this commentary strongly suggest that using urine as a marker of an environmental toxin is not necessarily reflective of a significant exposure," Dr. Brent writes. "Readers should use caution in interpreting more than the data actually indicate."
The BPA study was funded by the National Institutes of Health and supported by grants from the National Institute of Diabetes and Digestive and Kidney Diseases, the National Institute of Environmental Health Sciences, and the US Environmental Protection Agency. The phthalates study was supported by the KiDS of NYU Foundation. The authors and the commentator have disclosed no relevant financial relationships.
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Cite this: BPA, Phthalates Linked to Pediatric Health Risks - Medscape - Aug 19, 2013.