Hispanic women in Los Angeles exposed to air pollution, stress deliver lower-birth-weight babies: study

Hispanic women in Los Angeles who were exposed to air pollution and stress during pregnancy were more likely to deliver low birth weight babies, a new study has found.

Exposures to such contaminants and psychological stress disrupted delicate and precisely programmed fetal growth processes during early- to mid-pregnancy, according to the study, published on Tuesday in JAMA Network Open. 

“Although air pollution has a harmful effect on many different populations, our study identified the effects on expectant mothers who are already most vulnerable,” first author Zhongzheng (Jason) Niu, a postdoctoral scholar at the University of Southern California’s (USC) Keck School of Medicine, said in a statement. 

Infants with reduced birth weights face heightened risks of neonatal mortality and possible complications like breathing problems, brain bleeding, jaundice and infections, according to the authors. 

Low birth weight is also connected to the long-term development of certain diseases, such as diabetes, heart disease, high blood pressure, intellectual disabilities, metabolic syndrome and obesity.  

While scientists were already aware that air pollution is linked to lower birth weight and future disease risks, Niu explained that “the addition of high perceived stress is another factor” that exacerbates these circumstances. 

“Protecting pregnant women from these risks would ultimately protect future generations,” he said. 

To draw their conclusions, Niu and his colleagues said they combed through data from 2015-2021 from 628 predominantly low-income Hispanic pregnant women in Los Angeles. 

The data came from USC’s Maternal and Developmental Risks from Environmental and Social Stressors Center, while patients were primarily recruited from Eisner Health in downtown Los Angeles and the Los Angeles County/USC prenatal clinic. 

Clinicians collected bio-specimen data, medical records and residential information during patient appointments, and the mothers-to-be completed stress-level questionnaires to gauge their perceptions of stress, according to the study.

The researchers also assessed neighborhood-level stressors by using a statewide metric called CalEnviroScreen Score, which serves to pinpoint areas that have been disproportionately burdened by multiple sources of pollution. 

The average age of the patients was 28 years, with 73 percent self-identifying as Hispanic and 32 percent listing Spanish as their preferred language, according to the study. 

About 21 percent of the mothers reported high stress in their lives, while 60 percent lived in an area characterized by a disproportionately high pollution burden, the authors found. 

Using four local air monitoring stations, the researchers assessed the effects of three components of polluted air: PM 2.5 and PM 10 — particulate matter with diameters of less than 2.5 microns and less than 10 microns, respectively — as well as nitrogen dioxide. 

Pollution from PM 2.5 comes from the combustion of gasoline, oil, diesel fuel and wood, while PM 10 emissions are a result of dust and smoke, the authors noted.

Nitrogen dioxide is released when fossil fuels are burned at high temperatures, the researchers added.

Exposure to all the pollutants in early- to mid-pregnancy was associated with lower birth weight, the scientists found. 

However, those mothers who both had high stress scores and lived in the most environmentally burdened neighborhoods delivered babies with the greatest decreases in birth weight. 

Pregnant individuals in this group who were exposed to the highest levels of PM 2.5 while four to 20 weeks pregnant gave birth to infants weighing 34 grams (1.2 ounces) less in birth weight. 

Meanwhile, those exposed to the highest concentrations of PM 10 while nine to 14 weeks pregnant delivered babies weighing 39.4 grams (1.39 ounces) less, according to the study. 

Exposure to nitrogen dioxide had even greater impacts. Those women exposed while nine to 14 weeks pregnant gave birth to babies with a 40.4-gram (1.43-ounce) decrease in birth weight, the authors observed. 

Pregnant individuals exposed to nitrogen dioxide while 33 to 36 weeks pregnant reported the biggest reduction in birth weight: 117.6 grams (4.15 ounces), according to the study. 

“Despite reductions in air pollution in California, we are still seeing harmful effects of air pollutants on birth weight, a key indicator of baby’s future health, in vulnerable populations,” senior author Carrie Breton, a professor of population and public health sciences at the Keck School of Medicine, said in a statement. 

“The most vulnerable women are those who are hit with multiple types of stressors, and experience stress in different ways,” she continued.  

Going forward, Breton stressed the importance of considering a combination of stressors and pollutants in fostering healthy fetal growth. 

“Continuing to monitor air pollutants still needs to be a priority,” she added. “Reducing individual and neighborhood stressors should also be a priority, particularly at the policy level.”