Air pollution levels in Hong Kong have repeatedly reached dangerous levels in the last week, including on Monday morning. The South China Morning Post reported Monday that at times, the air quality was so bad that government recommendations encouraged everyone—even people without underlying health conditions—to stay inside.
Weather conditions, including wind patterns, over the last two days have contributed to the smog. However, some are concerned that the smog cannot be chalked up entirely to winter weather patterns. As Agence France-Presse reported, the number of days when smog posed a high health risk have doubled in the last year and environmental activists are pushing for more electric cars and cleaner fuels, despite a steady decline in pollution near roads.
Smog has become a perennial issue in Hong Kong. In just one month last winter, hundreds of thousands of Hong Kong residents went to their doctors' offices due to smog-related issues, the Guardian reported in February.
According to the Morning Post, nitrogen dioxide was the main reason that the air quality was so bad. Nitrogen dioxide "primarily gets in the air from the burning of fuel," according to the Environmental Protection Agency—basically, it comes from cars and other vehicles. When lots of it is in the air, nitrogen dioxide can make asthmatics' lives particularly difficult. It can also lead to increases in the levels of particulate matter and ozone levels through chemical reactions.
Ozone and particulates are both regulated as air pollutants in the United States, too. According to the Centers for Disease Control and Prevention's website, particulate matter is associated with heart and lung disease. Only two cities in the United States had air quality classified as "unhealthy for sensitive groups" on Monday. Both were in New Jersey.
Levels in Hong Kong have since declined a bit since Monday morning; by Monday night, only one station reported an Air Quality Health Index measure that landed in the "very high" health risk category. Air quality is also forecast to pose a moderate to very high health risk on Tuesday morning.
