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The Times of India, New Delhi, 13 November 2006
Benzene responsible for this spell of smog
Volatile Organic Compound Levels Rising: Study
Maneesh Pandey | TNN
New Delhi: As a thick blanket of smog smothers the city every morning, pollution
experts are not only pointing to the usual suspects — nitrogen oxides (Nox) and
ozone — this time. It’s the rising concentration of lesser-known volatile organic
compounds (VOCs) like benzene, toluene, xylene, styrene and butadine that’s
worrying them more.
The level of benzene, for one, is giving them quite a headache. While its
presence was in the range of 3-17 mg/m3 last year, it has jumped to 47 mg/m3 in
October this year. Says Anuradha Shukla of CRRI: ‘‘A study done by the CRRI at
Mathura Road found the concentration of benzene to be 34.474 mg/m3, as
against the global standard of 5-16 ug/m3, and that of toluene at 200 mg/m3,
which was higher than the WHO-prescribed weekly average concentration of 260
mg/m3.’’
These volatile organic compounds (VOCs) in the atmosphere react with
sunlight and Nox to give smog, which leaves particulate matter and groundlevel
ozone that is especially harmful for senior citizens, children, and people with
heart and lung conditions, bronchitis, and asthma.
Solvents used in paints, cosmetics, formaldehyde used in plywood products,
car exhaust, gasoline-powered lawn and garden equipment, and emissions from
industries are the key sources of VOCs. Benzene levels, in particular, can
increase from emissions from burning coal and oil, motor vehicle exhaust, and
evaporation from gasoline service stations. As tobacco contains high levels of
benzene, tobacco smoke is another source of benzene in air.
Even last year, the Central Pollution Control Board (CPCB) had reported
benzene levels in Delhi in the range of 3-17 mg/m3. ‘‘But the online and real time
monitoring in Siri Fort this year shows an alarming increase during the months of
October and November. It was as high as 47 mg/m3 towards the end of October.
The levels have remained high during November as well,’’ says Anumita
Roychowdhury of the Centre for Science and Environment (CSE).
So, why is this bad news? Breathing very high levels of benzene can cause
dizziness, rapid heart rate, headaches, tremors, confusion, and
unconsciousness. Long-term exposure can affect the bone marrow and decrease
red blood cells, leading to anemia. It can also cause excessive bleeding and
affect the immune system. Benzene is also considered as a potential carcinogen.
Evaporation during handling of crude oil and petrol is one of the main sources
of VOC emissions. ‘‘Delhi has already introduced 1% benzene petrol and a cap
on total aromatic content of petrol. Even then, benzene levels are increasing.
Clearly, we need close monitoring and a stronger benchmark for fuel quality. It is
also important to ensure that catalytic converters in all petrol vehicles are working
properly,’’ says Roychowdhury.
‘‘India has not yet set an ambient air quality standard for benzene or other
VOCs, but the current benzene levels in Siri Fort are high compared to the
European standard of 5 mg/m3 or even the UK standard of 16 mg/m3,’’ she says.
‘‘The standard of benzene is minimum in Japan, which has fixed it at 3 mg/m3,
followed by EU’s 5 mg/m3,’’ adds Shukla.
Incidentally, CPCB had proposed to set the air quality standard for benzene at
10 mg/m3 from 2005, but this has not been implemented. And while CRRI has
monitored air quality at ITO and Siri Fort intersections, its director P K Nanda
says, ‘‘There is need for more research on the pollution sources and the
quantification of emissions due to real traffic on a broader scale.’’
TOXIC TRAVAILS
What are VOCs?
They are volatile organic compounds which have high enough vapour pressure
under normal conditions to enter the atmosphere. A wide range of carbon-based
molecules, such as aldehydes, ketones, and hydrocarbons are VOCs
What are the sources?
Paint thinners, dry cleaning solvents, and some constituents of petroleum fuels
What are the health hazards?
Exposure to VOCs can cause eye allergy, choke upper respiratory tract, lead to
nasal congestion, rash, headache and nausea
Benzene, in particular, has been branded a carcinogen by the International
Agency for Research on Cancer. According to WHO estimates, lifetime exposure
to even 1 mg/m3 of benzene increases the risk of leukemia in four in one million
people
Breathing very high levels of benzene can result in death, while high levels can
cause drowsiness, dizziness, rapid heart rate, headaches, tremors, confusion,
and unconsciousness
Long-term exposure to benzene affects bone marrow, decreases red blood
cells, leading to anemia. It can also affect the immune system