Using the animal testing model, Texas A&M University researchers have found that harmful levels of ammonium sulfate in the atmosphere can produce birth defects and even fatalities during pregnancy.

The team of researchers from Texas A&M’s Colleges of Agriculture and Life Sciences and Geosciences and the Texas A&M Health Science Center joined with colleagues from the University of California-San Diego. Using female rats, the team examined the adverse health effects of exposure to fine particulate matter consisting of ammonium sulfate commonly found in many locations around the world. While large amounts can be found in Asia, it can also be found in Houston and Los Angeles.

Renyi Zhang, Texas A&M Distinguished Professor of Atmospheric Sciences, said in a telephone interview Friday that nine out of 10 people worldwide breathe air containing high level of pollutants, according to research done by the World Health Organization. About one of every nine global deaths can be attributed to exposure to air pollution, which totals more than 7 million deaths a year.

“People typically believe that ammonium sulfate may not be terribly toxic, but our results show large impacts on female pregnant rats,” Zhang said. “It is unclear yet what is causing these profound effects, but we speculate that the size of nanoparticles or even the acidity may be the culprit.”

Zhang said numerous studies have been done to show the insidious and dangerous shorter-term effects of air pollution, but far less data was available about its more lasting impacts.

“While epidemiological studies have been widely adopted to assess the health effects of air pollution, these tend to yield little insight into adverse outcomes and long-term effects,” Zhang said.

In the United States, about a third of the population lives under poor air quality conditions, according to a 2018 report from the U. S. Environmental Protection Agency. Zhang said that locally, the Brazos Valley can see its air quality negatively impacted by larger nearby cities, though at lower levels.

“In College Station, you can have blue skies, but have a lot of nanoparticles in the air,” he said. “In our study, we emphasized nanoparticles. The sky still looks blue, but nanoparticles can be even more dangerous.”

Zhang said that the animal model is a valuable approach to combine with epidemiological studies and make larger findings and “provide more insight into” potential health risks for humans, plant life and other animals in nature.  

He said sulfate is mainly produced from coal burning, which is a major energy source for much of the world in both developed and developing countries. Ammonium is derived from ammonia, which is produced from agricultural, automobile and animal emissions, “so this certainly represents a major problem worldwide,” Zhang said.

According to a university release, previous studies have shown pollution to impair metabolic and immune systems in animal offspring, but this research team’s study shows “definitive proof” of decreased fetal survival rates in rats, as well as shortened gestation rates that can result in smaller body weight. Damage to brains, hearts and other organs were also found in the adult rat models.

“However, our results show that prenatal exposure to air pollution may not dispose offspring to obesity in adulthood,” said Zhang’s colleague on the study, Guoyao Wu, who is a Texas A&M University Distinguished Professor.

“Nutrition and lifestyle are likely major factors contributing to the current obesity epidemic worldwide,” Wu said via a university release.

The researchers had their findings published in the current issue of PNAS (Proceedings of the National Academy of Sciences).

The team also found that during the winter months in India and China, where severe haze events frequently occur, fine particulate matter levels were especially high, at several hundred micrograms per cubic meter.

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