Low-income families are more likely to live in more polluted areas and also undergo more everyday stress, compared to their wealthier counterparts. For pregnant low-income women, that combination can prove harmful to the health of their fetuses, a new study has found.
Researchers at UC Berkeley and the University of California, San Francisco sifted through studies looking at exposure to both everyday stress and chemicals such as cigarette smoke and air pollution. In results published last month in the journal Plos One, the researchers found worse birth outcomes for chemical exposure alone than for chronic stress alone. But combined, the negative effects were multiplied. That result was even clearer for smoking than air pollution, as few studies looked at air pollution and stress together.
“We're just scratching the surface to try to understand the extent to which stress enhances vulnerability” to environmental pollution, said Rachel Morello-Frosch, a professor of environmental science, policy and management at UC Berkeley and one of the authors of the study.
Nayamin Martinez, the director of the Central California Environmental Justice Network, said communities that disproportionately experience pollution often accept it as a fact of life.
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Her agency is working to empower people by equipping neighborhoods with sensors that let them detect chemical hotspots. Martinez recounted the story of one town where chemical storage tanks were place next to a playground. Yet there was no regulation that could compel the company to move their tanks because they were classified as “small producers.”
While enough attention hasn’t been given to the issue, Martinez said, studies like the recent one are helpful to gather “data backing up what we know is happening, but we don't have the scientific evidence to prove it.”
The studies reviewed by UC researchers use factors such as socioeconomic status, education level and race to define low- and high-stress groups. The researchers then correlated women’s stress and chemical exposure, based on their location or testimony, with the babies’ birth weight.
Low birth weight, defined as less than 5 pounds, 8 ounces, puts infants at greater risk of health issues, and babies often have a harder time gaining weight and fighting infection. Later in life too, they may be more prone to health problems such as diabetes and heart disease.
More studies are needed to bolster the findings and reveal what’s going on in the body when it’s exposed to stress along with chemicals or pollution.
“It’s useful to stir more discussion and to suggest that we should be doing more. But it is not definitive,” said Beate Ritz, a professor of epidemiology at UCLA who also studies how environmental factors affect child development.
“This underlying chronic stress is something we need to be paying more attention to,” said Ritz. Her work has shown that the chronic, nagging stress of depression or the inability to improve circumstances can hurt birth outcomes even more than events such as a robbery or losing a job.
Several California areas have some of the country’s worst air quality, with seven of the state’s cities making it onto the American Lung Association’s top 10 most polluted U.S. cities list. The Sacramento metropolitan region checks in at No. 8 for ozone and No. 14 for spikes in particle pollution.
For a week or more, emissions can bake in the California sun to produce ozone, which causes asthma and lung problems.
The Los Angeles area, on the other hand, has better circulation but roughly 18 million people there emit much more. And many California cities suffer the pollution caused by being boxed in by highways, where cars on packed highways contribute to ozone and particle pollution.
The U.S. Environmental Protection Agency sets the limits for pollution exposure based on vulnerable groups, such as the elderly and children. “What this review suggests is that there are social factors that can also create vulnerable populations,” Morello-Frosch said.
“This gets at a lot of the environmental justice issues that communities have been raising for quite a while and now the science is starting to play catch-up.”