Quiz: Cadmium in food

Cadmium, a heavy metal that occurs naturally in the earth's crust, ranks high on the list of environmental toxins that pose considerable health threats. According to the Hong Kong Centre for Food Safety, cadmium is ingested mainly through food.

Plants, animals, fish and shellfish will absorb cadmium when grown in a contaminated environment. Human activities may also release cadmium into the environment. For smokers, tobacco smoke is a key source of cadmium exposure.

Cadmium exposure may lead to kidney dysfunction, osteoporosis, cancer, cardiovascular disease and other serious conditions. "Cadmium is virtually everywhere, and it is taken up into the human body and bio-accumulates for decades in the kidney," says Dr Stephan Clemens of the University of Bayreuth in Germany.

Clemens is the lead author of a study published earlier this month in the journal that examined how cadmium accumulates in certain plants. He suggests using breeding techniques to develop crops that transport less of the heavy metal to the grain.

The Joint Food and Agriculture Organisation/World Health Organisation Expert Committee on Food Additives has established a provisional tolerable monthly intake of 25 micrograms per kilogram of body weight. In Hong Kong, the Food and Environmental Hygiene Department has been conducting routine surveillance for cadmium and other heavy metals in foods collected from import, wholesale and retail levels.

Quiz yourself on cadmium below.

a. rice


b. choi sum

c. corn

a. abdominal cramps

b. flu-like symptoms

c. tingling hands

a. 0.1 to 0.2 microgram


b. 0.5 to 1 microgram

c. 1 to 2 micrograms

a. X-ray


b. blood test

c. urine test

1. a (it was reported that 10 per cent of Chinese rice contained excess cadmium); 2. all are correct; 3. c (and about 10 per cent is inhaled when cigarette is smoked); 4. b or c