Pollution zone

Published: Thursday 31 July 2008

-- Plants spell out air pollution in Varanasi

researchers at Benaras Hindu University (bhu) have used plants to study the impact of air pollution at the genetic level, the first-time ever, in Varanasi. They placed a locally available plant, Tradescantia pallida, at four locations, of which three were highly polluted. "We performed the experiment keeping in mind that the pollution in the city is very high between October and April," said Prajapati, the lead researcher.

They measured the concentration of various air pollutants including rspm (respirable suspended particulate matter--particulate matter less than 10 micron in size). While other pollutants were within the prescribed limit, rspm exceeded the permissible limit of 100 gm/m3 prescribed by the Central Pollution Control Board. "rspm was in the range of 105-150 gm/m3 at the three polluted sites and it could be detrimental to human health," he added.

The researchers collected young anthers from inflorescences to see the number of micronuclei in them. Micronuclei are dna-containing extra cellular bodies formed due to genetic aberrations.

"Formation of micronuclei is an abnormal condition where part of chromosomes break up and its nucleus forms many micronuclei, about 1/10th of the nucleus size," says Prajapati. The results showed that plants kept in areas having higher traffic emissions had higher micronuclei frequencies than samples kept at Sarnath, the fourth relatively unpolluted site.

Statistical analysis showed that frequency of micronuclei increased with increase in rspm level in the air. Increase in concentration of various pollutants led to damage at chromosomal level of the T. pallida plant. "Due to heterogeneity of air pollutants it was not possible to trace the particular compound that does the damage," said Prajapati.

"However, there is no evidence of the same phenomenon occurring in human beings," he said. According to M Agrawal, professor at department of botany in bhu, "Although genetic anomalies in plants and the risk of health problems in human cannot be equated, this experiment can be very useful as a proxy for assessing human risk. Particulates that carry heavy metals are most dangerous to human health, they accumulate in the leaves of the plant, contaminate the food chain."

"In a joint study with the Institute of Medical Science in the university, we have found a correlation between the concentration of NO2 and rspm inhaled and inadequate growth of the foetus during the last stages of pregnancy and increase in abortion due to birth defects, she added. The study was published recently in the journal Environmental International.

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