Higher ozone exposure linked to low birth weight in low- and middle-income countries 

Mohammed El-Said
8 Min Read

A new study has found that pregnant women who are exposed to ground-level ozone pollution are more likely to have low birth weight babies in low- and middle-income countries, such as the Middle East and North Africa. The study said that women who breathe ozone gas give birth to babies who weigh less than women who breathe cleaner air.

Ozone in the air we breathe can harm our health, especially on hot, sunny days when ozone reaches unhealthy levels. Researchers think that even relatively low levels of ozone can have negative health effects.

The study, published recently in the journal Science Advances, followed up on previous research that showed a link between ozone and low birth weight in high-income countries. To explore this issue, the researchers analyzed data on nearly 700,000 births in low- and middle-income countries.

“Good” ozone and “bad” ozone

Ozone gas, O3, is made of three oxygen atoms. It forms in the Earth’s atmosphere from emissions from polluting sources, such as carbon dioxide from car exhaust, volatile organic compounds from solvents, and methane from agriculture or power plants.

Ozone can be good or bad depending on where it is. Good ozone is naturally found in the upper atmosphere, the stratosphere, where it acts as a shield that protects living things from harmful ultraviolet rays and the damage of ozone layer depletion. But bad ozone is found at ground level, where it causes concern to researchers who believe it has harmful effects on human and plant health.

Study co-author Mingkun Tong, a professor of health sciences at Peking University in China, said that health problems that affect mothers and newborns are the main cause of neonatal death, and about 8% of newborn deaths are due to exposure to tiny pollutants called PM2.5 during preterm birth, which also lead to low birth weight.

The researchers tracked the condition of 697,148 newborns in 54 countries from 2003 to 2019. The team found that newborns from South Asia, North Africa, and the Middle East – except the Arab Gulf states – had the biggest reductions in birth weight because of ozone air pollution. The results also showed that low birth weight is linked to early death and many other health problems later in life.

The results agree with what a previous study published in August 2022 in the journal Environmental Pollution said, that pregnant women who are exposed to outdoor air pollutants – including ozone – have smaller babies, as well as a higher risk of preterm birth and various health problems later in life.

Tong points out that high temperatures in dry countries like Egypt make the effects of ozone gas on newborn health worse.

Low birth weight

Low birth weight refers to babies who are born weighing less than 2,500 grams (2.5 kilograms). A typical newborn baby weighs about 3,060 grams. A low birth weight baby may be healthy even if he is small. But a low birth weight baby can also face many serious health problems.

Many biological and behavioural factors can cause low birth weight, but the study showed that maternal exposure to outdoor air pollution, such as fine particulate matter (PM2.5) and ozone, can have a big impact. “Our findings show that ozone exposure is a major risk factor for low birth weight, especially in countries with high levels of air pollution in the Global South,” Tong says.

The researchers used ozone concentration data to estimate how much ozone gas the mothers breathed. They found that birth weight dropped by 19.9 grams for every extra 10 parts per billion of peak-season ozone concentration, a measure that the World Health Organization suggests as an indicator of long-term ozone exposure.

The authors estimate that in 123 low- and middle-income countries, the average low birth weight due to ozone exposure in 2019 was 43.8 grams. Ozone-related birth weight reductions were worst in the Middle East, South Asia, and North Africa. This effect was strongest in countries like India, Pakistan, Afghanistan, Egypt, Iraq, and Iran.

Mohamed Al-Basiouni, a professor of pediatrics at Mansoura University – Egypt, who did not take part in the study, explains that the peak time for ozone pollution is in the middle of the day – noon – and that the cleanest times of the day are in the early morning or at the end of the day. Al-Basiouni said that ozone gas raises the rate of asthma attacks and worsens complications in pregnant women, and the situation gets worse if the mother has heart problems.

Ozone also harms the nervous system of the fetus, according to the professor of pediatrics, who agrees with what the study authors said, that ozone gas affects the weight of the fetus and may lead to premature birth, as well as its effects on the behavioural and neurological development of the child.

Prevention is the solution

Al-Basiouni stresses the importance of early diagnosis of medical conditions related to air pollution with ozone gas so that its effects can be treated, but at the same time, he points out the importance of avoiding exposure to these pollutants and educating pregnant women to be careful and stay away from areas and times where pollutants are high.

The study’s co-author says the same: “Pregnant women can limit outdoor activities and stay indoors on days when ozone pollution is high. Also, air purifiers or specialized ozone removal filters with activated carbon may help lower pollutants.”

The World Health Organization’s air quality guidelines recommend that the peak season ozone exposure level be 60 µg/m3, so government agencies can set up and enforce their air quality standards and regulations to cut down ozone emissions, and healthcare providers can work together in public awareness campaigns to reduce ozone emissions, according to Tong, who also notes the need to educate pregnant women about the health risks of ozone pollution and provide advice on how to reduce exposure.

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Mohammed El-Said is the Science Editor for the Daily News Egypt with over 8 years of experience as a journalist. His work appeared in the Science Magazine, Nature Middle East, Scientific American Arabic Edition, SciDev and other regional and international media outlets. El-Said graduated with a bachelor's degree and MSc in Human Geography, and he is a PhD candidate in Human Geography at Cairo University. He also had a diploma in media translation from the American University in Cairo.
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