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Chinese experts have blamed the volatile organic compounds in hair spray, perfume and air refreshers for the recurring air pollution in the country as the dreaded smog returned to haunt the Beijing city on Monday.
The air quality index in Beijing climbed to 213, which is categorised by the World Health Organisation, (WHO) as "very unhealthy".
Beijing, the city of over 21-million people, every year experiences the problem of air pollution, which in recent years has dropped to moderate levels following series of measures initiated by the government since 2015 restricting the use of coal and shifting polluting industries out of the range.
China has been fighting a tough war against smog for years. It has cut life expectancy in some Chinese regions and the government has asked its citizens to buy masks and air purifiers to protect themselves during peak pollution days.
Beijing has a four-tier alert system for pollution, with red the highest, followed by orange, yellow and blue.
The orange alert means the air quality index is forecast to exceed 200 for three consecutive days.
During high alerts, heavy polluting vehicles and trucks carrying construction waste are banned from roads and some manufacturing firms cut production.
The Beijing Municipal Environmental Protection Bureau reported on Thursday that from January to September, the average concentration of PM 2.5 in Beijing dropped by 16.7 per cent compared to last year.
While several studies have been conducted on the reasons for heavy pollution in Beijing and Northern part of China attributing to heavy industrialisation and emissions of automobiles, experts now blame the volatile organic compounds (VOCs) for contributing to the poor air quality in the city.
The VOCs are a group of carbon-based chemicals that easily evaporate at room temperature. Many common household materials and products, such as paints and cleaning products, give off the VOCs.
The VOC compounds comprise 12 per cent of PM 2.5 in Beijing, and call for regulating these "less significant" sources, state-run Global Times quoted experts as saying.
The VOCs are concentrated in aerosols like perfume, hair gel, insecticide and cleaning agents, as well as kitchen and gas stations, Wang Gengchen, a research fellow at the Chinese Academy of Sciences' Atmospheric Physics Institute, told the daily.
These VOCs do not directly produce PM 2.5, but generate particle pollutants through a series of physical and chemical reactions, Wang said.
A Beijing Municipal Environmental Protection Bureau report released in May said that life emissions account for 12 per cent of the city's total emissions, which equals industrial emission.
Shi Aijun, deputy dean of the Beijing Academy of Environmental Sciences, told Science and Technology Daily that the proportion of pollution caused by everyday life activities is increasing in Beijing.
"The data is only an estimate," Wang said, adding that the ratio will decline in winter when coal burning increases and urban areas will see a higher concentration than the suburbs.
Policies should be made to deal with indirect pollution sources since strict measures have already been taken on vehicles and coal burning which contribute to almost half of the total PM 2.5 in Beijing, Wang said.
These "less significant" sources (VOCs) should not be ignored, Peking University Professor Tang Xiaoyan told the Science and Technology Daily on Saturday.
