The U.S. has seen child obesity rates rise significantly over the last two decades, with low-income and racial/ethnic minority children particularly affected. Even at very young ages, many inner-city children show elevated rates of overweight and obesity. Data from the National Health and Nutritional Examination Survey (NHANES) for 2003-2004 indicate that the national prevalence of overweight (≥ 85th and <95th percentile in BMI for age/gender) among children ages 2-19 is 16.5% and the prevalence of childhood obesity (≥ 95th percentile in BMI for age/gender) is 17%.
New York City has particularly suffered from this epidemic of childhood obesity. Recent studies of NYC children show that 15-19.4% of children are overweight and an additional 22-27% of children are obese. We see similar trends in our cohort study: 21% of 5 year olds were obese, as were 25% of those followed to age 7. These trends are concerning and have significant public health implications: childhood obesity is associated with increased risk of metabolic syndrome, type 2 diabetes, and cardiovascular disease and thus poses a major health issue in the years to come.
What We Know
Early-life exposures to environmental endocrine disruptors may be contributors to obesity.
Endocrine disruptors are chemicals that mimic, block, or disrupt hormones. This disruption can halt or increase production of hormones, or change the way hormones travel through the body.
The rise in childhood obesity clearly has multiple causes, with the bulk of the literature, both scientific and lay press, identifying both individual behavior (e.g., high fat diets, sedentary behavior) and societal and systemic issues (e.g., suburbanization, car dependence, and agricultural and food policies) that contribute to this increase. However, there is an emerging hypothesis that prenatal and early life exposures to environmental endocrine disruptors play a role in the obesity epidemic by altering metabolic programming in childhood.
Endocrine Disrupting Chemicals: Polycyclic Aromatic Hydrocarbons (PAH) and Bisphenol-A (BPA)
Polycyclic aromatic hydrocarbons (PAH) are a family of chemicals created during the incomplete combustion process of fossil fuels. They are a known carcinogen to humans and they also have endocrine disrupting effects. Evidence, including our own, suggests that exposure to PAH tends to be disproportionately high among low-income, urban and minority populations because of the disproportionate location of outdoor pollution sources in these areas, which include diesel bus depots and major commercial roadways.
Bisphenol-A (BPA) is found in polycarbonate plastics and epoxy resins. It is one of the highest volume chemicals produced worldwide, with over six billion pounds produced each year. Human exposure to BPA is widespread, including in our own Center cohort in New York City. However, effects of chronic, low-dose BPA exposure in children are largely unknown.
Prenatal PAH and Obesity
Several lines of research indicate that exposure to PAH is associated with higher weight, with human data showing effects of prenatal exposure. Recent cell culture and mouse studies suggest that PAH alters fat metabolism and induce weight gain. Mouse studies have shown that exposure to PAH causes gains in fat mass, while cell culture studies have shown that exposures to PAH prevent normal lipolysis, the process by which fat cells shed lipids and shrink in size. Another line of research implicating PAH in weight gain is the literature available on the effects of smoking during pregnancy. Cigarette smoke contains high concentrations of PAH, and numerous human studies have shown that, despite the negative effects on birth weight, smoking during pregnancy is associated with higher weight in offspring, with effects seen in childhood, adolescence and into adulthood.
Our own findings from the Mothers and Newborns study, which follows pregnant women and children in New York City from birth to adolescence show that exposure to higher concentrations of PAH increased obesity risk: children of women exposed to high levels of PAH during pregnancy were nearly twice as likely (1.79 times) to be obese at age 5, and more than twice as likely (2.26 times) to be obese at age 7, compared with children of mothers with lower levels of exposure. The 7-year-olds whose mothers were in the highest exposure group had, on average, 2.4 lbs. more fat mass than did children of mothers with the lowest exposure.
Prenatal BPA and Obesity
There have been relatively few epidemiologic studies on effects of BPA on obesity and related health outcomes. However, a 2008 cross-sectional study of 1,455 adults sampled in NHANES found that urinary BPA concentrations were significantly associated with risk of diabetes and cardiovascular disease. In a small study from Japan, BPA concentrations were significantly higher among the 7 obese women compared to the 19 non-obese women, with a positive correlation between BPA and BMI. The Center has been exploring the relationship between obesity and BPA in our New York City cohort. The work is currently ongoing.
The Center’s obesity studies are one of the first to present evidence that chemicals in the environmental can contribute to obesity in human beings. Future research will focus on identifying other examples of these “obesogens” and ways to reduce them.
What You Can Do
Get involved in community and nationwide efforts to improve outdoor air quality:
- Report idling vehicles to 311.
- Support the NYC government initiative to require all buildings to burn #2 fuel oil.
- Sign up for air quality updates at Clean Air NY
- Add your air pollution solution to plaNYC and help spread ideas how to make our city a greener, greater place to live
- For more community resources you can contact our lead community partner, WE ACT for Environmental Justice
- Call the Environmental Protection Agency today to put BPA on the “Chemical of Concern List” — (202) 564-4332 or email: PolicyOffice@epa.gov
- Ask your senator to co-sponsor the Safe Chemicals Act
- Contact your favorite companies and tell them to make BPA-free products
- Ask your employer to use BPA-free products
Fresh indoor air is important for your family’s health. Reduce indoor air pollution through the following ways:
- Do not smoke & do not let others smoke in your home
- When cooking and grilling make sure there is appropriate ventilation by using fan or open window
- Leave windows open in good weather to allow indoor air to be replaced by fresh outdoor air. However, if the outdoor air pollution index is high, keep windows closed until conditions improve.
- Use low-VOC paints
- Clean the filters of your air conditioner and dehumidifier regularly
- Eat a diet full of fresh fruits and vegetables since they are a great source of antioxidants that can offset the affect of PAH exposure
- Dust with a damp cloth regularly
- Try to avoid using spray pesticides and learn about integrated pest management IPM Brochure (English) and IPM Brochure (Spanish)
Avoid possible BPA exposure in food and baby formula
- Try not to microwave, boil and freeze plastics. Instead, heat food and drinks in containers made from ceramic or porcelain, or glass, or stainless steel.
- Wash plastics by hand, NOT in dishwasher.
- Avoid old or scratched plastics– recycle them instead.
- Nurse your baby when possible. By breastfeeding, you give your baby healthy nutrients. If you cannot nurse, try powdered formula; liquid formulas in cans may contain BPA.
- Only use plastic containers like baby bottles labeled “BPA-free”
- Replace canned goods with paper cartons or glass jars-especially if the food is acidic like tomatoes (BPA is found in the lining of canned goods). Save money by using dried beans, legumes, and grains
Receipts can also contain BPA. If you don’t need it, don’t grab it!
- Place receipts in envelopes
- Keep away from children
- Wash hands with soap and water after touching receipts & money.
- Try not to hold receipts with wet hands or after using lotion or sanitizer (they can let BPA get into the skin easier)
Learn Your Numbers: Plastic Labels
- Find recycling labels on the bottom of plastics. Some plastics are more harmful than others. Less harmful plastics are labeled with a 1,2,4, or 5 — they are not known to leach any chemicals that are suspected of causing cancer or disrupting hormones.
- Avoid plastics labeled with 3,6, or 7
- BPA is marked “PC” or the recycling label #7
- Label #6 or “PS” is Styrofoam. Benzene (material used in production) is a known human carcinogen. Butadiene and styrene (the basic building block of the plastic) are suspected carcinogens.
- Label #3 or “PVC” is Vinyl. To soften into its flexible form, manufacturers add “plasticizers” during production. Traces of these chemicals can leach out of PVC when in contact with foods.