Delhi: How vehicular emissions are fuelling assault on your health
NEW DELHI: A new study gives a full-year characterisation of volatile organic compounds (VOCs), which are gases emitted into the air when anything is burnt that has carbon during industrial processes or use of certain machines.
The study found that vehicular emissions and solid fuel combustion were the dominant sources of VOCs in Delhi.
Scientists monitored VOCs for 146 days in 2019 for four seasons — summer, monsoon, post-monsoon and winter. The traffic-related emissions, they said, contributed about 31% of the VOCs measured over the entire period and were significant over the year, comprising about one-third of all the sources. Solid fuel combustion factors, consisting of phenols, furans and nitrogen-containing compounds, contributed about 28%, while secondary VOCs contributed about 31%. The formation of secondary VOCs depends on meteorological conditions and primary VOCs.
According to the study, titled “Seasonal variability and source apportionment of non-methane VOCs using PTR-TOF-MS measurements in Delhi”, VOCs have an adverse impact on health, and citing a few previous studies, it stated that in urban and industrial areas, exposure to elevated levels of certain VOCs, such as benzene, toluene, xylene and ethylbenzene (BTEX), could cause acute and chronic health conditions, including sperm abnormalities, reduced fetal growth, cardiovascular disease, respiratory dysfunction and asthma. Benzene and BTEX are also carcinogenic.
The study was carried out by scientists from IITs in Kanpur, Delhi and Jodhpur, and Physical Research Laboratory, Ahmedabad, and accepted in the “Atmospheric Environment” journal.
The average concentration was found to be the highest in post-monsoon (October-November) at 199.6 parts per billion volume (ppbv). It was 151.2pppv in monsoon (July-September), 131.3ppbv in winter (December-February) and 78.7ppbv in summer (March-June). There is no prescribed standard for VOCs, except for benzene at 5µg/m3 and benzo(a)pyrene at 1ng/m3. Seasonal variation of VOCs’ sources describes the importance of meteorology and season-specific activities.
Sachchida N Tripathi of the civil engineering department at IIT Kanpur, the lead author of the study, said, “VOCs have harmful effects on health and they also condense into particulate matter and, thereby, contribute to organic aerosol formation.” He added, “VOCs are precursors to organic aerosols, therefore identification of their sources is important to design effective mitigation strategy.”
In this study, for the first time, emissions from vegetation contributing towards biogenic sources were quantified. It contributed around 9.4% and 4.3% during summer and monsoon, respectively. “Trees also emit VOCs and due to higher temperature in summer, the volatility was higher,” said Tripathi.
The research said a stringent mitigation and control action plan was needed to reduce primary non-methane VOC sources such as vehicular emissions and solid fuel combustion. “The results will be important for not only the academic community, but also for the policy-makers to make informed decisions for the abatement of non-methane VOCs,” the study emphasised. “These compounds are responsible for the formation of secondary organic aerosols and ozone (O3), their control strategies will also reduce O3 and particle pollution in the city,” it added.