| Yummy, but... Diwali sweets wrapped in silver foil
New Delhi, Nov. 1: Scientists have detected high levels of lead on thin food-grade silver foil used on Indian sweets and are questioning the age-old tradition of giving sweets a cosmetic coat of silver.
Indian food laws specify that food-grade silver foil should be 99.9 per cent pure, but are silent about the remaining 0.1 per cent of its makeup. This leaves a margin of 1000 parts per million for contaminants.
Scientists at the Industrial Toxicology Research Centre in Lucknow analysed 161 silver foil samples and found that more than half failed to meet the required purity of 99.9 per cent. Half of the foil samples studied contained lead. Copper was present in 86 per cent of the samples and cadmium in 28 per cent, the scientists said in a research paper set to appear in a forthcoming issue of the international journal, Food Additives and Contaminants.
We wanted to find out what the other 0.1 per cent of foil contains, said Mukul Das, head of the food toxicology division at the centre. This study tells us that it is important for food standards authorities to specify limits for heavy metals in foil, Das said.
The average level of lead in contaminated foil samples was 301 micrograms per gram. This is unacceptably high, said Thuppil Venkatesh, head of biochemistry and director of the national lead poisoning centre at St Johns Medical College in Bangalore.
Lead has no useful biological function in the body, Venkatesh said. The average lead level in the foil samples was 6000 times higher than the maximum permissible limit of lead in water set by the World Health Organisation ' 50 micrograms per kg.
While eating a few sweets coated with foil would not lead to dangerously high lead levels in the body, the scientists said the lead concentrations they detected in the foil justify concerns about long-term exposure from prolonged consumption.
On prolonged exposure, even low concentrations (5 micrograms per decilitre) of lead in the blood can lead to genetic damage. At twice that concentration, lead can begin to impair the intellectual abilities of young children, Venkatesh said.
Several Indian sweets, including burfi, gulab jamun, malai pan, and laddoos, have silver foil coatings.
Das said the lead may creep in as a contaminant either during the purification of the silver or while it is being flattened into the shape of a foil. Processing agents used during purification may be a source of lead, he said.
The team observed workers pounding silver into a foil. They would place silver ribbons between two flat sheets made out of the intestinal walls of cattle or deer and hammer the silver into the flattened foil shape.
Small-scale industries refused to reveal details of how they produced the flat sheets from animal entrails. They considered it a trade secret, said Das. We just dont know where the lead comes from, he said.
Venkatesh said the study should provide reason enough to question the use of silver in sweets. It has no other purpose except making them look good.
Das said eliminating the use of silver foil would need a change in public attitudes. It would help to recall that all that glitters isnt gold, he said.
The centre had picked up 178 samples of foil from small-scale processing units around Lucknow and found that only 161 were silver foils. The other 17 were aluminium foils but fraudulently labelled silver.