Watch before you eat

Air pollution contributes to heavy metals in vegetables

By Biplab Das
Last Updated: Saturday 04 July 2015

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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  • It is astonishing and

    It is astonishing and terrifying information because we as nutritionists recommend higher intake of green leafy vegetables. With the results of the study of BHU it is necessary to think before recommending. Further research is needed to prove absorption of these heavy metals

    Posted by: Anonymous | 8 years ago | Reply
  • Its not about the green leafy

    Its not about the green leafy vegetables but the manner they are grown and cultivated. If the farms are located by the railway tracks or by the highway where there is heavy flow of traffic, there is bound to be heavy concentration of heavy metals in the air. There are numerous studies to prove that heavy metals are absorbed in the body. Another reason is cultivation near polluting industries which spoils the groundwater. hence the way out is to eat organic vegetables or to buy from a fixed vegetable vendor who can source least contaminated vegetables. Personally, certified organic vegetables are better as they can be trusted most.

    Posted by: Anonymous | 8 years ago | Reply