Mix of stress and air pollution may lead to cognitive difficulties in children

January 16, 2020

Science Daily/Columbia University's Mailman School of Public Health

Children with elevated exposure to early life stress in the home and elevated prenatal exposure to air pollution exhibited heightened symptoms of attention and thought problems, according to researchers at Columbia University Mailman School of Public Health and Columbia Psychiatry. Early life stress is common in youth from disadvantaged backgrounds who also often live in areas with greater exposure to air pollution.

Air pollution has negative effects on physical health, and recent work has begun to also show negative effects on mental health. Life stress, particularly early in life, is one of the best-known contributors to mental health problems. The new study is one of the first to examine the combined effects of air pollution and early life stress on school-age children. Results appear in the Journal of Child Psychology and Psychiatry.

"Prenatal exposure to polycyclic aromatic hydrocarbons, a neurotoxicant common in air pollution, seems to magnify or sustain the effects of early life social and economic stress on mental health in children," says first author David Pagliaccio, PhD, assistant professor of clinical neurobiology in psychiatry at Columbia Psychiatry.

"Air pollutants are common in our environment, particularly in cities, and given socioeconomic inequities and environmental injustice, children growing up in disadvantaged circumstances are more likely to experience both life stress and exposure to neurotoxic chemicals," says senior author Amy Margolis, PhD, assistant professor of medical psychology in psychiatry at Columbia Psychiatry.

"These exposures have a combined effect on poor mental health outcomes and point to the importance of public health programs that try to lessen exposure to these critical risk factors, to improve not only physical, but psychological health," says Julie Herbstman, PhD, associate professor of environmental health science and director of the Columbia Center for Children's Environmental Health at Columbia Mailman School of Public Health.

Data were from the CCCEH Mothers and Newborns longitudinal birth cohort study in Northern Manhattan and the Bronx, which includes many participants who self-identify as African American or Dominican. Mothers wore an air monitoring backpack during the third trimester of pregnancy to measure exposure to air pollutants in their daily lives. When their children were 5 years old, mothers reported on stress in their lives, including neighborhood quality, material hardship, intimate partner violence, perceived stress, lack of social support, and general distress levels. Mothers then reported on their child's psychiatric symptoms at ages 5, 7, 9 and 11.

The combined effect of air pollution and early life stress was seen across several measures of thought and attention problems/ADHD at age 11. (Thought problems included obsessive thoughts and behaviors or thoughts that others find strange.) The effects were also linked to PAH-DNA adducts -- a dose-sensitive marker of air pollution exposure.

The researchers say PAH and early life stress may serve as a "double hit" on shared biological pathways connected to attention and thought problems. Stress likely leads to wide-ranging changes in, for example, epigenetic expression, cortisol, inflammation, and brain structure and function. The mechanism underlying the effects of PAH is still being interrogated; however, alterations in brain structure and function represent possible shared mechanistic pathways.

Earlier studies making use of the same longitudinal cohort data found that prenatal exposure to air pollution combines with material hardship to significantly increase ADHD symptoms in children. A separate study found a combination of air pollution and poverty lowered child IQ.

https://www.sciencedaily.com/releases/2020/01/200116155436.htm

Flame retardants and pesticides overtake heavy metals as biggest contributors to IQ loss

January 14, 2020

Science Daily/New York University

Adverse outcomes from childhood exposures to lead and mercury are on the decline in the United States, likely due to decades of restrictions on the use of heavy metals, a new study finds.

Despite decreasing levels, exposure to these and other toxic chemicals, especially flame retardants and pesticides, still resulted in more than a million cases of intellectual disability in the United States between 2001 and 2016. Furthermore, as the target of significantly fewer restrictions, experts say, flame retardants and pesticides now represent the bulk of that cognitive loss.

NYU Grossman School of Medicine researchers found that IQ loss from the toxic chemicals analyzed in their study dropped from 27 million IQ points in 2001 and 2002 to 9 million IQ points in 2015 and 2016.

While this overall decline is promising, the researchers say, their findings also identify a concerning shift in which chemicals represent the greatest risk. Among toxin-exposed children, the researchers found that the proportion of cognitive loss that results from exposure to chemicals used in flame retardants, called polybrominated diphenyl ethers (PDBEs), and organophosphate pesticides increased from 67 percent to 81 percent during the same study period.

"Our findings suggest that our efforts to reduce exposure to heavy metals are paying off, but that toxic exposures in general continue to represent a formidable risk to Americans' physical, mental, and economic health," says lead study investigator Abigail Gaylord, MPH, a doctoral candidate in the Department of Population Health at NYU Langone. "Unfortunately, the minimal policies in place to eliminate pesticides and flame retardants are clearly not enough."

The substances analyzed are found in household products from furniture upholstery to tuna fish, and can build up in the body to damage organs, researchers say. Heavy metals, lead and mercury in particular, are known to disrupt brain and kidney function. In addition, they, along with flame retardants and pesticides, can interfere with the thyroid, which secretes brain-developing hormones. Experts say exposure at a young age to any of these toxins can cause learning disabilities, autism, and behavioral issues.

In their investigation, the researchers found that everyday contact with these substances during the 16-year study period resulted in roughly 1,190,230 children affected with some form of intellectual disability. Overall childhood exposures cost the nation $7.5 trillion in lost economic productivity and other societal costs.

"Although people argue against costly regulations, unrestricted use of these chemicals is far more expensive in the long run, with American children bearing the largest burden," says senior study author Leonardo Trasande, MD, MPP, the Jim G. Hendrick, MD Professor at NYU Langone Health.

Publishing online Jan. 14 in the journal Molecular and Cellular Endocrinology, the new study is the only long-term neurological and economic investigation of its kind, the authors say. The investigators analyzed PBDE, organophosphate, lead, and methylmercury exposures in blood samples from women of childbearing age and 5-year-olds. Data on women and children was obtained from the National Health and Nutrition Examination Survey.

The researchers used results from several previous environmental health studies to estimate the annual number of IQ points lost per unit of exposure to each of the four main chemicals in the study. Then, they estimated the lost productivity and medical costs over the course of the children's lives linked to long-term intellectual disability using a second algorithm, which valued each lost IQ point at $22,268 and each case of intellectual disability at $1,272,470.

While exposure to these chemicals persists despite tightened regulations, experts say Americans can help limit some of the effects by avoiding the use of household products or foods that contain them.

"Frequently opening windows to let persistent chemicals found in furniture, electronics, and carpeting escape, and eating certified organic produce can reduce exposure to these toxins," says Trasande, who also serves as chief of environmental pediatrics in the Department of Pediatrics at NYU Langone.

Trasande notes that the impact of these chemicals may be worse than their study can capture since there are far more hazards that affect brain development than the four highlighted in the investigation, and other potential consequences beyond IQ loss. "All the more reason we need closer federal monitoring of these substances," she says.

The study authors say they plan to explore the cost of exposure to endocrine-disrupting chemicals in other countries.

https://www.sciencedaily.com/releases/2020/01/200114101724.htm