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Food colours are being added to a sweet food.—Fahim Siddiqi/White Star
Food colours are being added to a sweet food.—Fahim Siddiqi/White Star

KARACHI: Samples of unbranded food colours collected from various parts of the city have been found to have high concentration of heavy metals, a study conducted recently said.

Titled Assessment of heavy metals in locally available unbranded food colours available in the vicinity of Karachi, the study was conducted by Dr Aamir Alamgir Khan, Sundus Fatima and Nimra Ayub under the supervision of Prof Moazzam Ali Khan at Karachi University’s Institute of Environmental Studies.

Under the study, 48 locally available unbranded samples of food colours (green, red, orange, purple, yellow and maroon) were collected from Malir, Shah Faisal Colony, PIB Colony, Gulshan-i-Iqbal, Saddar, Surjani Town, Nazimabad, Federal B Area, Quaidabad and Sohrab Goth.

These samples were tested to check the level of nickel, cadmium, arsenic, chromium and lead.

‘Children at high risk of poisoning if they consume them regularly’

“During sample collection, we saw that these food colours are not only purchased by the general public for use in traditional dishes, they are also used by local street vendors for preparing drinks, candies, sweets, gola ganda as well as dairy products,” Dr Aamir Alamgir at the IES told Dawn.

People of Karachi especially children were at a high risk of metal poisoning, if they consumed these types of products on regular basis, he added.

According to Dr Khan, food colours are either produced naturally or derived synthetically and undergo assessment, like other food additives, in developed countries.

The case of Pakistan is, however, different where there is little regulation on food manufacturers.

“There are no national guidelines on food colour. Internationally, however, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) is responsible for evaluating the safety of food additives,” he said.

The WHO, he said, encouraged national authorities to monitor and ensure that food additives in food and drinks produced in their countries comply with permitted uses, conditions and legislation.

According to the general FAO/WHO guideline, the maximum allowable limit for lead in food products is 0.1ppm, 0.2ppm for nickel, 0.1ppm for arsenic and 0.1ppm for cadmium.

There are no guidelines available for chromium in food.


The analysis showed that nickel concentration in samples ranged between 1.42ppm and 4.77ppm (parts-per million) whereas cadmium concentration ranged between 0.16ppm and 1.81ppm.

Most samples had arsenic traces below detectable limits. The maximum level of arsenic was observed in maroon colour (0.153ppm), collected from Federal B Area.

The highest concentration of nickel (4.77ppm) and cadmium (1.81ppm) was found in orange samples collected from Liaquatabad and Malir Halt, respectively.

Lead concentration varied between 1.24ppm and 6.38ppm. The minimum and maximum concentration of lead was observed in maroon samples collected from PIB Colony.

The minimum concentration of chromium (0.36ppm) was found in green samples collected from PIB Colony while the maximum concentration of chromium (3.89ppm) was found in red samples collected from Liaquatabad.

Use of low cost natural mineral pigments, according to researchers, is the main source of such metal contamination in food products as they contain cadmium, lead, arsenic and chromium.

The use of arsenic contaminated water and nickel as preservative in processing and packaging as well as poor quality utensils used in food preparation were other sources of contamination, the study said.

“Living organisms require varying amounts of heavy metals, for instance iron, zinc, copper and manganese. All metals, however, are toxic at higher concentration,” Dr Khan explained, adding that human body could get exposed to heavy metals through different sources, including polluted air.

“Harmful effects depend on the duration and intensity of metal exposure to human body. In the case of food, it is important to see how frequently contaminated food is being taken as heavy metals start getting deposited in the body and negatively affect different organs, if they exceed certain limit,” he said.

At high levels of acute exposure, lead damaged brain and central nervous system to cause coma, convulsions and even death. At lower levels of exposure that caused no obvious symptoms and that previously were considered safe, lead was now known to produce a spectrum of injuries to the human body, Dr Khan said, adding that there appeared to be no threshold level below which lead caused no injury to the developing human brain.

“The biological effects of chromium strongly depend on its specific chemical form. The health hazards associated with exposure to chromium are dependent on its oxidation state,” he said, emphasising the need for regulating food products.

Published in Dawn, March 19th, 2018