Study: New Delhi Is Again World’s Most Polluted Capital
新德里再次成为全球污染最严重城市
New Delhi was the most polluted capital city last year, just like it was in 2018. That finding comes IQ AirVisual, a Swiss-based group that studies air-quality measurements from around the world.
India was home to 21 of the world's 30 most polluted cities, the group reported.
该组织报告称，全球污染最严重的30个城市中，有21个位于印度。
IQ AirVisual said the study measured levels of a kind of particulate matter (PM), called PM2.5, in major population centers.
IQ AirVisual称，这项研究测量了主要人口中心一种被称为PM2.5的颗粒物的水平。
Researchers chose to examine PM2.5 because it "is the pollutant widely regarded as most harmful to human health," the report said.
研究人员选择检查PM2.5，因为它“被公认为对人体健康最有害的污染物。”
These small particles, less than 2.5 microns in length, can go deep into the lungs. High PM2.5 levels can cause health problems, including cancer and heart disease, the report notes.
Researchers examined data about PM2.5 concentrations in the air. The information was collected hourly, from ground-based monitoring systems.
研究人员检查了空气中的PM2.5浓度数据。这些信息每小时会通过地面检测系统收集一次。
In 2019, New Delhi's average yearly concentration of PM2.5 in a cubic meter of air was 98.6, the report said. That is more than twice the level of Beijing, which had an average of 42.1 during the year. Beijing was the ninth most polluted capital city, the study found.
New Delhi's harmful air has a number of causes. They include pollution from motor vehicles and industrial centers, dust from building projects and smoke from the burning of waste.
Late last year, rising air pollution levels forced Indian officials, who called the crisis a public health emergency, to close schools twice.
去年年底，不断上升的空气污染水平迫使印度官员两度下令学校停课，官员称这一危机是公共卫生紧急事态。
The study, however, said India did see "widespread improvements" in PM2.5 levels compared to 2018. These improvements were likely a result of better weather conditions, government cleanup efforts, and an overall economic slowdown.
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