Students' dietary exposure to lead is well below the provisional tolerable weekly intake set by the World Health Organisation, a Food & Environmental Hygiene Department study has found.

The department today told lawmakers 345 food samples were taken for analysis by its Food Research Laboratory.

The dietary exposure to lead for an average secondary school student was estimated to be 1.98μg/kg bw/week while that for the high consumers was 5.09. Both figures are well below the World Health Organisation's provisional tolerable weekly intake figure of 25.

The department said both average and high consumers among students are unlikely to experience major toxicological effects from lead in food.

Main source

The main dietary source of lead identified in the study were vegetables, which contributed to about 58% of total food exposure. This was followed by food groups "meat, poultry, eggs and their products" and seafood which contributed 21% and 15% of total exposure.

Fruit and cereals accounted for 4% and 2% of total exposure while milk and dairy products accounted for less than 1%.

Further analysis on meat, poultry, eggs and their products found that lime-preserved eggs had the highest level of lead, which alone accounts for 79% of the contribution by this food group or 17% of total dietary exposure.

Traditionally, lead compounds have been used for processing lime-preserved eggs. However, alternate methods which use copper or zinc compounds to replace the lead are available.

Excluding these eggs, dietary exposure to lead from other foods in the group was only 0.09 μg/kg bw/week, or 5% of total dietary exposure.

Oyster alert

Oysters were found to have the second highest level of lead in the study. Exposure from oysters accounts for 8% of total dietary exposure, or half of the seafood contribution.

Vegetables should be washed and soaked thoroughly to remove dust and soil and to reduce lead levels. Before preparing food, wash hands.