Millions of children worldwide develop asthma annually due to traffic-related pollution

About 4 million children worldwide develop asthma each year because of inhaling nitrogen dioxide air pollution, according to a study published today by researchers at the George Washington University Milken Institute School of Public Health (Milken Institute SPH). The study, based on data from 2010 to 2015, estimates that 64 percent of these new cases of asthma occur in urban areas.

The study is the first to quantify the worldwide burden of new pediatric asthma cases linked to traffic-related nitrogen dioxide by using a method that takes into account high exposures to this pollutant that occur near busy roads, said Susan C. Anenberg, PhD, the senior author of the study and an associate professor of environmental and occupational health at Milken Institute SPH.

"Our findings suggest that millions of new cases of pediatric asthma could be prevented in cities around the world by reducing air pollution," said Anenberg. "Improving access to cleaner forms of transportation, like electrified public transport and active commuting by cycling and walking, would not only bring down NO2 levels, but would also reduce asthma, enhance physical fitness, and cut greenhouse gas emissions."

The researchers linked global datasets of NO2 concentrations, pediatric population distributions, and asthma incidence rates with epidemiological evidence relating traffic-derived NO2 pollution with asthma development in kids. They were then able to estimate the number of new pediatric asthma cases attributable to NO2 pollution in 194 countries and 125 major cities worldwide.

Key findings from the study published in The Lancet Planetary Health:

  • An estimated 4 million children developed asthma each year from 2010 to 2015 due to exposure to NO2 pollution, which primarily comes motor vehicle exhaust.
  • An estimated 13 percent of annual pediatric asthma incidence worldwide was linked to NO2 pollution.
  • Among the 125 cities, NO2 accounted for 6 percent (Orlu, Nigeria) to 48 percent (Shanghai, China) of pediatric asthma incidence. NO2's contribution exceeded 20 percent in 92 cities located in both developed and emerging economies.
  • The top 10 highest NO2 contributions were estimated for eight cities in China (37 to 48 percent of pediatric asthma incidence) and for Moscow, Russia and Seoul, South Korea at 40 percent.
  • The problem affects cities in the United States as well: Los Angeles, New York, Chicago, Las Vegas and Milwaukee were the top five cities in the U.S. with the highest percentage of pediatric asthma cases linked to polluted air.
  • Nationally, the largest burdens related to air pollution were found in China at 760,000 cases of asthma per year, followed by India at 350,000 and the United States at 240,000.

Asthma is a chronic disease that makes it hard to breathe and results when the lung's airways are inflamed. An estimated 235 million people worldwide currently have asthma, which can cause wheezing as well as life-threatening attacks.

The World Health Organization calls air pollution "a major environmental risk to health" and has established Air Quality Guidelines for NO2 and other air pollutants. The researchers estimate that most children lived in areas below the current WHO guideline of 21 parts per billion for annual average NO2. They also found that about 92 percent of the new pediatric asthma cases that were attributable to NO2 occurred in areas that already meet the WHO guideline.

"That finding suggests that the WHO guideline for NO2 may need to be re-evaluated to make sure it is sufficiently protective of children's health," said Pattanun Achakulwisut, PhD, lead author of the paper and a postdoctoral scientist at Milken Institute SPH.

The researchers found that in general, cities with high NO2 concentrations also had high levels of greenhouse gas emissions. Many of the solutions aimed at cleaning up the air would not only prevent new cases of asthma and other serious health problems but they would also attenuate global warming, Anenberg said.

Additional research must be done to more conclusively identify the causative agent within complex traffic emissions, said the researchers. This effort, along with more air pollution monitoring and epidemiological studies conducted in data-limited countries will help to refine the estimates of new asthma cases tied to traffic emissions, Anenberg and Achakulwisut added.

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Materials provided by George Washington University. Note: Content may be edited for style and length.


Asthma may contribute to childhood obesity epidemic

Toddlers with asthma are more likely to become obese children, according to an international study led by USC scientists.

The finding is a turnabout for children's health as obesity has often been seen as a precursor to asthma in children, not the other way around. The study, conducted by a team of 40 scientists including researchers at the Keck School of Medicine of USC, was recently published in the European Respiratory Journal.

This is the largest study yet about early-onset asthma and obesity. It focused on more than 20,000 youths across Europe. It shows that, beyond wheezing and shortness of breath, asthma can lead to bodies that make young people more susceptible to other health problems later in life.

Lida Chatzi, the senior author and professor of preventive medicine at USC, says asthma and obesity pack a one-two punch against children's health, which raises concern about a public health crisis due to their prevalence.

"We care about this issue because asthma affects approximately 6.5 million children -- about one in 10 -- in the United States," Chatzi said. "It's a chronic childhood disorder and if it increases the risk of obesity, we can advise parents and physicians on how to treat it and intervene to help young children grow up to enjoy healthy, adult lives."

For two decades, scientists have documented the parallel epidemics of childhood asthma and obesity, with focus on how obesity is a risk factor for asthma. In adults, obesity is an important risk factor for new asthma, especially among women, but the relationships appear to differ in children. Few studies look at the problem the other way around to understand how asthma contributes to obesity in kids, which prompted scientists to undertake this research.

Drawing upon big data on children's health collected across Europe, the scientists investigated 21,130 children born between 1990 and 2008 across nine countries, including Denmark, France, Germany, Greece, Italy, the Netherlands, Spain, Sweden and the United Kingdom.

The children were diagnosed by physicians with asthma at 3 to 4 years old and the scientists followed toddlers into childhood up to 8 years of age. Their goal was to focus on health risks of early-onset asthma.

On average, the scientists found that children diagnosed with asthma had a 66 percent higher risk of becoming obese than those without an asthma diagnosis. For children with persistent wheezing symptoms, their risk of developing obesity was 50 percent greater compared to children without such symptoms. Children with active asthma were nearly twice as likely to develop obesity than those without asthma and wheezing, according to the study. The findings are consistent with previous, but smaller, longitudinal studies conducted in the United States that observed asthma increased the risk of obesity.

The causal direction between asthma and obesity is not well understood. Asthma is regarded as a barrier to children's physical activity that might lead to accumulation of fat in the body, while higher doses of inhaled corticosteroids had been hypothesized to increase risk of obesity in children with asthma. According to the study, children with asthma who used medication had the strongest risk of developing obesity.

Since both asthma and obesity have their origins early in life, it is possible that the asthma-obesity association is also established in this critical time window of child development. Previous studies have shown that in utero exposures, such as prenatal diet or maternal obesity, are associated with increased risk of both disorders.

"Asthma may contribute to the obesity epidemic. We urgently need to know if prevention and adequate treatment of asthma can reduce the trajectory toward obesity," said Frank Gilliland, professor of preventive medicine at the Keck School of Medicine, who participated in the study.

According to the U.S. Centers for Disease Control and Prevention, about 40 percent of Americans, or 93 million, are obese. The estimated annual medical cost of obesity nationwide was $147 billion in 2008, the CDC estimates. Obesity is linked to diseases such as diabetes, high blood pressure and stroke.

The CDC reports the number of people with asthma in the United States is growing every year. About one in 12 Americans is afflicted with the illness. In smoggy places, like California's San Joaquin Valley, about 1 in 6 children suffer from asthma, the highest rate in the country.

In Europe, 1 in 8 people die due to lung diseases -- or about one person per minute. It includes well-known diseases like asthma and lung cancer and other less-known diseases like chronic obstructive pulmonary disease, which is now the third most common cause of death, according to the European Respiratory Society.

Testosterone explains why women more prone to asthma

An international research team has revealed for the first time that testosterone protects males against developing asthma, helping to explain why females are two times more likely to develop asthma than males after puberty.

The study showed that testosterone suppresses the production of a type of immune cell that triggers allergic asthma. The finding may lead to new, more targeted asthma treatments.

One in nine Australians (2.5 million people) and around one in 12 Americans (25 million) have asthma, an inflammatory airway condition. During an asthma attack, the airways swell and narrow, making it difficult to breathe. In adults asthma is two times more prevalent and more severe in women than men, despite more being more common in boys than girls before puberty.

In 2016, the city of Melbourne, Australia, experienced a 'thunderstorm asthma' event that was unprecedented internationally in its scale and severity of consequences, with almost 10,000 people visiting hospitals over a two-day period. Thunderstorm asthma refers to allergic asthma thought to be initiated by an allergy to grass pollen. Many people with no history of asthma experienced severe asthma attacks.

Dr Cyril Seillet and Professor Gabrielle Belz from Melbourne's Walter and Eliza Hall Institute, with Dr Jean-Charles Guéry and his team at the Physiopathology Center of Toulouse-Purpan, France, led the study, published today in the Journal of Experimental Medicine.

Dr Seillet said hormones were speculated to play a significant role in the incidence and severity of asthma in women. "There is a very interesting clinical observation that women are more affected and develop more severe asthma than men, and so we tried to understand why this was happening," Dr Seillet said.

"Our research shows that high levels of testosterone in males protect them against the development of allergic asthma. We identified that testosterone is a potent inhibitor of innate lymphoid cells, a newly-described immune cell that has been associated with the initiation of asthma."

The research team found that innate lymphoid cells -- or ILC2s -- 'sensed' testosterone and responded by halting production of the cells.

"Testosterone directly acts on ILC2s by inhibiting their proliferation," Dr Seillet said. "So in males, you have less ILC2s in the lungs and this directly correlates with the reduced severity of asthma."

ILC2s are found in the lungs, skin and other organs. These cells produce inflammatory proteins that can cause lung inflammation and damage in response to common triggers for allergic asthma, such as pollen, dust mites, cigarette smoke and pet hair.

Professor Belz said understanding the mechanism that drives the sex differences in allergic asthma could lead to new treatments for the disease.

"Current treatments for severe asthma, such as steroids, are very broad based and can have significant side effects," Professor Belz said.

"This discovery provides us with a potential new way of treating asthma, by targeting the cells that are directly contributing to the development of allergic asthma. While more research needs to be done, it does open up the possibility of mimicking this hormonal regulation of ILC2 populations as a way of treating or preventing asthma. Similar tactics for targeting hormonal pathways have successfully been used for treating other diseases, such as breast cancer."

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