Watch before you eat

Air pollution contributes to heavy metals in vegetables

By Biplab Das
Published: Tuesday 31 January 2012

FARMERS in urban outskirts mostly rely on wastewater for growing vegetables. The level of air pollutants like aerosols is also high in these areas. Scientists have found that both these factors have a cumulative effect on the quality of the vegetables.

The research by Banaras Hindu University (BHU) has shown that plants grown in such conditions have high levels of heavy metals which exceeds the limits set under the Prevention of Food Adulteration Act of 1954.

imageThe researchers grew spinach, radish and tomato in earthen pots and exposed them to both aerosols and wastewater. The pots were placed at three different sites— Tadia, a rural agricultural belt, Cantonment area and a highway near BHU campus in Varanasi. Pots exposed to clean water at the BHU campus acted as control.

Deposition was found to be maximum for lead followed by copper, nickle, chromium and cadmium. Among sites, aerosol deposition was found to be maximum at the highway—the region receives high dose of pollutants from heavy vehicles, small-scale industries and railway emissions.

The team found that the vegetables exposed to both aerosol and wastewater accumulated 10–30 per cent higher amounts of heavy metals in edible parts like leaves, fruits and roots. The results also showed that the accumulated heavy metals contribute to dietary intake of them ranging from 1.34 to 110.40 microgram per gram through leaves (spinach), 1.04 to 105.86 microgram per gram through root (radish) and 0.608 to 82.19 microgram per gram through fruits (tomato).

Wastewater irrigation led to more accumulation in the root vegetables while air pollution resulted in more metals in leafy vegetables. The researchers also reported higher levels of heavy metals in vegetables than observed earlier.

Cadmium can cause cancer while lead can lead to behavioural problems, learning disabilities, seizures and even death. Nickel can cause allergic reaction and copper if ingested in high dose can lead to harmful effects on DNA. Kumar Shubhashish, one of the researchers says, that besides posing a threat to people who consume such vegetables, such accumulation also decimates soil microbial population, which, in turn, disrupts soil nutrient cycling, leading to deterioration of soil sustainability and food quality.

The study will be published in the February issue of Ecotoxicology and Environmental Safety.

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