Decline in urinary bisphenol A concentrations in the United States.

To the Editor: Bisphenol A (BPA) is a highvolume production chemical used in polycarbonate plastics and epoxy resins. Human exposure occurs when BPA leaches from packaging into food or water. BPA has been associated with adverse reproductive, cardiometabolic, and behavioral outcomes, resulting in public and scientific concern.1–4 This concern, particularly for children, has led to the production of BPA-free products.2,5 Prior reports noted a possible decrease in urinary BPA after 2003–20043,6; however, more recent data are now available. We assessed time trends, especially among children, using National Health and Nutrition Examination Survey (NHANES) 2003–2010 data. Spot urine samples were obtained in 10,415 persons from four consecutive 2-year NHANES cycles (www.cdc. gov/nchs/nhanes.htm). Urinary BPA was analyzed using high-performance liquid chromatography-tandem mass spectrometry; this method did not change over time. The limit of detection (LOD) was 0.4 ng/ml: LOD/√2 was used for values below LOD (7.0%) (see eTable 1, http:// links.lww.com/EDE/A634). To account for urine dilution, BPA was creatininecorrected (BPAcorr) or adjusted for creatinine in models. We carried out statistical analyses using Stata 11.2 (College Station, TX), accounting for survey design and incorporating appropriate sample weights. Geometric mean BPAcorr levels by year were calculated. We assessed the percentage difference in BPA over time, adjusting for creatinine, age, sex, race/ethnicity, and income, using linear regression models with 2003–2004 as the reference category. To determine when substantial changes in BPA concentrations occurred within the study time frame, we further examined the percentage difference between consecutive survey cycles. Geometric mean BPAcorr was 2.09 μg/g creatinine (95% confidence interval [CI] = 2.02–2.16). BPA concentrations were higher in 2003–2004 compared with later years (eTable 2, h t tp : / / l inks . lww.com/EDE/A634; Fig.). In adjusted models, among 6to 11-year-olds, 12to 19-year-olds, and those 20 years or older, the percentage difference in BPA comparing 2009– 2010 to 2003–2004 was −45 (95% CI = −55 to −32), −40 (−49 to −28), and −20 (−23 to −2), respectively (eTable3, h t tp : / / l inks . lww.com/EDE/A634; Fig.). When comparing each cycle with the previous one, we observed significant decreases from 2003–2004 to 2005–2006 among all age groups and from 2007–2008 to 2009–2010 among 6to 11-year-olds, but a significant increase from 2005–2006 to 2007–2008 among those 20 years or older (eTable 4, http://links.lww.com/EDE/A634). Urinary BPA concentrations declined from 2003 to 2010 among younger children; however, among young people of age 12–19 years and those 20 years or older, there was a decline only from 2003–2004 to 2005–2006. This analysis is consistent with prior reports but includes more recent data and specifically focused on time trends. As has been suggested previously, this decline might represent random variation6; however, it is also plausible that there has been a true reduction in BPA exposure. As early as 2003, public concern about BPA generated advice on how to avoid exposure,7 by changing consumption habits; this has been shown to affect urinary BPA concentrations.8 In addition, removal of BPA from products would reduce exposures. It will be important to continue monitoring BPA concentrations, as additional removal of BPA from products may further reduce body burdens. It is also important to consider what is used as a substitute, to avoid merely replacing one endocrine disruptor with another.5 In conclusion, BPA concentrations have declined among 6to 11-year-olds in recent years, but remain highest in this age group, which may be the most vulnerable to environmental toxicants.1 Additional research should consider the health effects of BPA exposure particularly in the pediatric population, where outcomes—especially those related to obesity and cardiovascular risk—remain relatively understudied.