Wednesday, April 18, 2018

AQI to monitor air quality should also include the toxic VOCs

Air pollution has become a matter of great concern now both for the environment as well as human health. But, when we talk of air pollution, it is the particulate matter, both PM2.5 and PM10, which garner the most attention. Most advisories for air pollution also define actions to control ‘particle’ pollution and how to avoid exposure to particulate matter. But, we ignore other important pollutants such as volatile organic compounds or VOCs, which are gases that are released into the air from products or processes. 

VOCs can be present in both indoor and outdoor environments.

Sources of indoor VOCs include household products like cleaners and disinfectants, paints and other solvents, air fresheners, cosmetics and deodorants, acetone in nail polish removers, dry-cleaned clothing, and pesticides. Glues and adhesives, permanent markers, varnishes, photographic solutions, copiers and printers are other sources of indoor VOCs.

Petroleum products and diesel, wood burning, industrial emissions and chemical solvents are sources of outdoor VOCs.

VOCs are the main precursors to the formation of surface or ground level or tropospheric ‘bad’ ozone and particulate matter, which together form smog. Smog is known to have adverse effects on human health and the environment. Chemical reactions between nitrogen oxides (NOx) and VOCs in sunlight form the ground level ozone, which is harmful, unlike the ozone layer high up in the atmosphere, which acts as a shield and protects from harmful UV rays. The thinning of this stratospheric ‘good’ ozone layer is seen as a hole, colloquially called ‘ozone hole’. Traffic emissions constitute more than half of the ozone precursors.

Acute exposure to VOCs causes irritation of the eyes, nose and throat, headaches, loss of coordination and nausea. Long-term exposure damages the liver, kidneys and the brain.

Some VOCs such as benzene are suspected or known to cause cancer in humans. The International Agency for Research on Cancer (IARC) has classified benzene as Group 1 carcinogen i.e. confirmed as carcinogenic to humans. World Health Organization (WHO) guidelines on benzene say that “No specific guideline value has been developed for air. Benzene is carcinogenic to humans, and no safe level of exposure can be recommended”.

The AQI takes into consideration eight pollutants (PM10, PM2.5, NO2, SO2, CO, O3, NH3 and Pb) and their levels are constantly monitored. However, the AQI does not monitor the quantity of VOCs.

But, VOCs are also major toxic air pollutants, which are also hazardous to human health, more so, because they are also present in high concentrations in the indoor environment causing prolonged exposure. VOCs have long-term adverse effects on health unlike particle pollutants, which have immediate impact such as acute asthma exacerbation or an acute cardiac event. Benzene, a VOC, is a known human carcinogen.  

There is therefore a need to create public awareness about VOCs, their sources and harmful effect on health as a first step towards controlling and preventing exposure to this health hazard. Also, regulations should be in place to monitor the environmental levels of these toxic air pollutants.

Dr KK Aggarwal
Padma Shri Awardee
Vice President CMAAO
Group Editor-in-Chief IJCP Publications
President Heart Care Foundation of India
Immediate Past National President IMA

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