New Delhi: Around 86 percent of people living in urban areas worldwide, the equivalent of about 2.5 billion people, are exposed to unhealthy particulate matter levels. This resulted in 1.8 million more deaths in cities globally in 2019, according to a new study published in Lancet Planetary Health magazine.
According to another study published in the same journal, nitrogen dioxide (NO2) pollution caused nearly 2 million asthma cases in children worldwide in 2019. Two out of three cases occurred in urban areas.
The studies highlight the need for strategies to improve air pollution and reduce the risk of harmful emissions, especially among children and the older generation.
PM2.5 resulted in 1.8 million more deaths in 2019
In the first study, the researchers focused on PM2.5, which are fine particles 2.5 micrometers or less in diameter.
PM2.5 is the major environmental risk factor for disease, and its inhalation is known to increase the risk of premature death from conditions such as heart disease, respiratory disease, lung cancer and lower respiratory infections.
More than 55 percent of the world’s population lives in cities. Yet, there has been little research on how the PM2.5 disease burden in urban areas compares to a global scale to date. In most of the estimates, PM2.5 was analyzed only in megacities. In the new study, researchers examined PM2.5 concentrations and related mortality in more than 13,000 cities globally between 2000 and 2019.
There was a wide variation in PM2.5 by region. The largest regional growth was observed in urban areas in Southeast Asia, including India. Between 2000 and 2019, the average population-weighted PM2.5 concentration had increased by 27 percent.
In Southeast Asian countries, the death rate due to PM2.5 in 100,000 people increased from 33 percent to 63 percent to 84 percent. According to the first study, these countries saw the highest increase in mortality due to PM2.5.
The World Health Organization (WHO) 2005 Guidelines for Annual Average PM2.5 Exposure states that the annual mean concentration of PM2.5 should not exceed 10 micrograms per cubic metre. Also, the 24-hour average exposure should not exceed 25 micrograms per cubic meter more than three times a year.
The study noted that in 2019, around 86 percent of urban residents worldwide lived in areas exceeding WHO guidelines, resulting in more than 1.8 million deaths.
Over two decades, decreasing PM2.5 in urban areas did not correspond to the same level of reduction in PM2.5-attributable mortality in countries, the researchers found.
For example, African, European, and North and South American cities saw 18 percent, 21 percent, and 29 percent reductions in PM2.5 concentrations.
The fact that the reduction in concentrations did not correspond to the same level of reduction in mortality due to PM2.5 indicates that other demographic factors, such as an aging population and poor general health, are influential factors of pollution-related mortality. are drivers, the study said.
A Lancet statement, citing Veronica Southerland of George Washington University in the US and lead author of the study, said that much of the world’s population still lives in areas with unhealthy levels of PM 2.5. Avoiding the large public health burden caused by air pollution will require strategies that not only reduce emissions but also improve overall public health to reduce vulnerability, he said.
Limitations of the study included the fact that some uncertainties in the values could not be fully accounted for, such as the use of nationwide baseline disease rates in the calculation of mortality. In addition, the study only assessed the effect of 2.5 on mortality, without accounting for other health burdens caused by PM 2.5, such as low birth weight, premature birth and cognitive impairment, the study authors wrote. mentioned in.
Air pollution in cities responsible for two-thirds of asthma cases in children
In the second study, the researchers focused on NO2, an air pollutant emitted by vehicles, power plants, industrial construction, and agriculture. NO2 serves as a marker for transport-related air pollution. According to previous research, transportation-related air pollution is associated with both asthma exacerbations and new-onset asthma in children. However, to date, there has been no study that specifically looked at the trends in the burden of transport-related NO2 pollution or pediatric asthma incidence in urban areas.
The researchers calculated global NO2 concentrations with up to one kilometer resolution by combining satellite data with datasets on different types of land uses, such as roads and green space.
To estimate the incidence of pediatric asthma due to NO2 between 2000 and 2019, in 13,189 urban areas around the world, researchers applied NO2 concentrations to population and baseline asthma rates, the study said.
In 2019, there were 1.85 million new pediatric asthma cases associated with NO2, the researchers found. Also, it was 8.5 per cent of all new cases reported that year.
Two of the three pediatric cases caused by NO2 occurred in the 13,189 urban areas included in the study. In 2019, NO2 was responsible for 16 percent of all new pediatric asthma cases in urban areas.
At least 1.2 million pediatric asthma cases in urban areas can be attributed to NO2 pollution in both 2000 and 2019, the study said.
However, the rate fell from 176 per 100,000 children to 156 per 100,000 children. With an increase of 14 percent in the urban population, the rate decreased by 11 percent.
The Lancet statement, citing Dr Susan Annenberg of George Washington University in the US and first author of the study, said the study results demonstrate the significant impact of combustion-related air pollution on the health of children in cities globally. Huh. She is also the corresponding author of both studies. Annenberg said NO2 concentrations have been trending downward for decades in locations with effective air quality management programs, and this has been beneficial to children’s respiratory health.
They noted that despite these improvements, current NO2 levels continue to contribute significantly to the incidence of pediatric asthma. This highlighted the fact that reducing air pollution should be an important element of children’s public health strategies.
Limitations of the study included the fact that baseline pediatric asthma rates in low- to middle-income countries may have been underestimated, leading to an underestimation of the effects of asthma due to NO2.
In addition, due to the lack of data on urban rates and the prevalence of asthma within countries, national pediatric asthma rates were used.
The authors noted in the study whether the incidence of pediatric asthma is linked to NO2, a traffic-related air pollution mix, or a widespread combustion-related air pollution mix.
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