KARACHI: While the Sindh government is yet to wake up to the growing threat of contaminated food chain, a local study has shown that commonly consumed food items, such as chicken meat, lentils and even potatoes, both in raw and cooked form, are tainted with metals known for causing human poisoning.

Titled An experimental study of arsenic and lead concentration in common food sources, the study has recently been published in the International Journal of Community Health Sciences.

The Department of Community Health Sciences of Aga Khan University has collaborated with the Department of Environmental and Preventive Medicine of Jichi Medical University in Japan for the study, which was conducted by Dr Abdul Ghani, Dr Ambreen Sahito, Dr Shahla Naeem, Dr Zafar Fatmi and Dr Fujio Kayama.

Samples of lentils, potatoes and chicken meat were brought from the open market in Karachi. They were washed and cooked for 20 minutes in tap water in utensils made of aluminium, iron, stainless steel and black-coated non-stick cookware.

Levels of arsenic and lead were assessed both in raw and cooked form of these food items.

None of them is found free of lead, arsenic

The study’s findings showed that none of the food items were free of lead and arsenic. The concentration of lead and arsenic in tap water was 1.3ng/g and 2.5ng/g, respectively.

Uncooked potato had 10.3ng/g of lead and 3.5ng/g arsenic. The concentration of lead in chicken and potato cooked in iron cookware was 23ng/g and 13.4ng/g, respectively.

Lentils cooked in aluminium and steel cookware had high concentration of lead (55.1 and 34.6ng/gm, respectively). The arsenic level was high in cooked chicken muscle meat regardless of type of cooking utensils and ranged from 41.3ng/g to 47.7ng/g compared to other food items.

“The chicken meat was uniformly contaminated with high arsenic levels irrespective of the utensil material used for cooking. Thus, chicken meat could be potentially contaminated from external environment (mostly likely during poultry raising). Aluminium or steel utensils have particular interaction with lentils and cause leaching of lead during cooking,” it says.

‘Safe levels’

According to the study, the provisional tolerable weekly intake (PTWI) for arsenic was withdrawn by Joint Food and Agricultural Organisation/World Health Organisation’s Expert Committee on Food Additives (JECFA) in 2011 because of the uncertainty regarding its safety for human health.

Reports suggest that lower levels of arsenic below PTWI levels were also associated with lung cancers. Exposure to 0.01–0.04 mg/kg/day arsenic is reported to increase the risk for several internal cancers and adverse health outcomes.

Lead exposure, according to the WHO, is preventable but there is no known level of lead exposure that is considered safe.

“Lead in the body is distributed to the brain, liver, kidney and bones. It is stored in the teeth and bones, where it accumulates over time. Human exposure is usually assessed through the measurement of lead in blood.

“Lead can have serious consequences for the health of children. At high levels of exposure, lead attacks the brain and central nervous system to cause coma, convulsions and even death. Children who survive severe lead poisoning may be left with mental retardation and behavioural disorders,” the WHO says.

Sources of contamination

The study also points to the possible sources of lead contamination and says that despite control of lead in petrol since 2001, studies have reported high blood lead levels in Pakistan. Exposure still occurs through secondary sources (mainly food) due to its widespread contamination of the general environment.

The groundwater in Indus river, it says, is contaminated with arsenic and approximately 13 million people are potentially exposed in Pakistan. Also, several food items including vegetables, grains and fish have been reported to be contaminated with arsenic, mainly by groundwater.

“The experiment was a part of larger observational study conducted in urban and rural Sindh which was conducted to determine lead and arsenic exposure to pregnant women, newborns and children. It was found that the weekly arsenic intake by young children through food was high (188 µg/kg bw) and around 14pc of the children’s weekly arsenic intake was exceeding the provisional tolerable weekly intake (PTWI) level.

“The logical next step was to identify the main sources of food commonly contributing to high level of exposure among the vulnerable population. This study confirms that the common food items consumed by the population including lentils, potato and chicken were contaminated with lead and arsenic,” it says.

It suggests investigation into poultry vaccination and feed in Pakistan where chicken feed is mostly prepared from small-sized sea and freshwater fish, waste materials of animals (blood and non-consumable parts) and low-quality grains.

It cites another study which reported that chicken feed in poultry farms may contain arsenic as high as 43.7µg/g (43700ppb). Findings also showed direct strong relationship of the accumulation of arsenic in different tissues of broiler chicken and amount of arsenic in feed.

Studies have also shown that arsenic is excreted by chickens in their manure and remains in the environment for longer time.

These excretory products are used as fertilisers in agricultural fields, elevating soil arsenic loads and leading to expanded chain of human arsenical exposure.

It recommends researching other food items especially those for children, the junk foods which are being frequently consumed, for analysing concentration of arsenic and lead.

“Chronic exposure to lead and arsenic have potential for increasing the risk for cancerous and non-cancerous disease burden. Therefore, strict enforcement of regulation regarding prevention of contamination, during raising of chickens, processing and packaging of food items is required. Exposure from lead and arsenic can be reduced by regulating food items and quality of cooking utensils,” it suggests.

Published in Dawn, August 22nd, 2018