Particulates blown away but ozone emerges as primary health threat

Gurugram : 25 June, 2019 (Hindustan Times)

Gurugram has recorded five days in June when ozone was the city’s ‘prominent pollutant’, CPCB data shows

GURUGRAM: While the city is currently witnessing its best air in weeks with lower than usual levels of atmospheric particulate matter (PM), another pollutant— ozone — has emerged as the primary threat to citizens’ health.

Gusty winds, which varied between the speeds of 35 and 40 kmph, were recorded in the city on Monday evening.

So far this month, Gurugram has recorded five days when ozone was the city’s ‘prominent pollutant’, data from the Central Pollution Control Board (CPCB) has showed. During the same period last year, the prominent pollutant was recorded as PM2.5 on all days, indicating that concentration of ground-level ozone is on the incline this summer.

According to a recent analysis of CPCB data by the Centre for Science and Environment (CSE), Gurugram had unsafe levels of ozone on at least 15 days between April 1 and June 15, whereas CPCB data shows that there were only three days during the same period last year when ozone exceeded the safe limit.

On June 23, for example, the concentration of ozone touched 222ug/m3. Such spikes were also reported on June 20, when ozone levels touched a maximum of 256ug/m3, and on June 8 when it touched 268ug/m3, the highest concentration recorded in the city this year.

Experts called this trend alarming as prevalence of ground-level ozone, in turn, proves that other pollutants, such as NOX and SOX are also present in high quantities.

Polash Mukherjee, an air quality expert with the National Research Development Corporation (NRDC) of India, explained, “Ozone is a composite, or secondary pollutant, which is formed due to chemical reactions undergone by other pollutants, such as sulphur oxides and nitrogen oxides. Heat, which is a catalyst, facilitates these reactions. Hence, higher concentrations of ozone are seen during summer months.”

This explanation was seconded by Namita Gupta, a citybased air quality consultant. Gupta said that the presence of sunlight has a direct impact on formation of ground-level ozone.

“The reasons for particularly high ozone levels this summer can be attributed to the recent heat wave, and generally higher temperatures as compared to last year.”

Due to the direct impact of heat and sunlight, ozone is present in higher quantities during the day, and begins tapering off after noon every day. This is also reflected in CPCB’S daily data for Gurugram. Unlike the ‘good’ ozone present in the earth’s ozone layer, which protects us from harmful ultraviolet (UV) radiation, ground-level ozone can have adverse impacts on human health, experts warned.

Nirajan Raje, a former member of the Supreme Court mandated Environment Pollution Control Authority (EPCA) and a Gurugram resident, said that the health risk associated with ozone pollution is high because of its invisibility. “One cannot see ozone, which is a gaseous pollutant. But one can feel ozone. It causes irritation of skin, tighten ing of chest, and other issues. In summer months, people tend to ascribe these symptoms as a direct result of heat. This is only partly true,” Raje said, adding that ozone is a highly reactive gas and can severely exacerbate respiratory ailments, such as asthma.

Increasing levels of ozone have also been reported from neighbouring Delhi. According to the CSE, Delhi recorded ozone as its primary pollutant for 17 days between April 1 and June 15 last year. During the period this year, that number rose to 28 days.

To deal with this problem, CSE recommended that governments take active steps to curb vehicular emissions, increase electric mobility, scale up public transport and pedestrian infrastructure, deploy citywide parking management to curb use of private vehicles, and aggressively control industrial emissions. Kuldeep Singh, regional officer, Haryana State Pollution Control Board (HSPCB), declined to provide a comment. 

Causing several health problems


Ozone is formed through photochemical reactions involving pollutants like nitrogen oxide and volatile organic compounds that take place in the presence of sunlight Days in June when ozone was the dominant pollutant What is ozone pollution?

Ozone occurs in both the upper atmosphere of the earth (i.e. the 'ozone layer') and at the ground level. The ozone in the atmosphere protects us from harmful ultraviolet rays, whereas ground level ozone is a harmful pollutant.

Ground-level ozone is not directly emitted into the air by vehicles, industries, waste burning or other primary sources. It is formed by chemical reactions between oxides of nitrogen, carbon monoxide and volatile organic chemicals in the presence of sunlight and heat.

High levels of ozone indicate prevalence of pollution from primary sources, such as industries, vehicles, diesel generator sets and others.

Ozone concentrations tend to peak on hotter, sunnier days. Ground-level ozone can also be transported over long ranges by winds, which gain velocity on hotter days.

What are its effects ?

Breathing ozone can induce chest pain, coughing, throat irritation and airway inflammation. Ozone can also harm lung tissue and reduce lung function, worsen bronchitis and asthma.

Children, senior citizens, and those suffering from prior respiratory illnesses are particularly vulnerable. Those with specific genetic characteristics, such as people with low intake of vitamins C and E, are at greater risk from exposure.

Exposure to ozone is particularly high risk as it is an invisible pollutant, and its presence cannot be picked up by low-cost air quality monitors, which only detect particulate matter.