Melamine contamination highlights food chain risks

Hong Kong mother Shirley Lo stocked her refrigerator with soymilk and switched to buying imported chocolates for her son after melamine was found in baby formula and milk products in China.

But when eggs from China tested positive for melamine in Hong Kong late last month, Ms Lo threw up her hands in despair.

"It's horrifying," she said. "It's clear it has gone into basic foods and into our food chain. My son has been trying to comfort me, saying he must be very strong because his body must be full of this stuff and yet he is not sick".

The discovery of melamine in eggs as well as in baby formula, milk products, biscuits, chocolates and other foodstuffs containing milk derivatives confirms what experts have long suspected; that the chemical is deeply embedded in the human food chain.

And it's not just melamine; heavy metals such as lead and mercury which can cause brain damage, as well as cadmium, a compound used in batteries, pesticides and antibiotics are all present in the human food chain.

"In China, food safety is not a concern and all sorts of things like Sudan red, Malachite green are added in food, so food contamination is widespread," said Peter Yu, a professor of biology and chemical technology at the Hong Kong Polytechnic University.

The melamine saga has surprised even some food producers, who say they find it hard to keep up with strange additives that are added to food. Melamine, for example, was added to baby formula to cheat protein level tests.

Tens of thousands of children in China have fallen ill with kidney problems in recent months, and at least four have died, after being fed infant formula that was later found to have been mixed with melamine.

But with the discovery of melamine in eggs, apparently due to contaminated feed given to chickens, the chemical appears to be far more entrenched in the human food chain than first thought.

Melamine and its derivatives are widely used in animal feed and pesticides in China but no one knows how harmful they can be to people after prolonged exposure.

Experts say the limits are arbitrary and called for more tests and science when imposing safety limits.

"The limits are derived from animal studies but we don't know what our exposure is. What if we are accumulating more than is safe?," said Chan King-ming, biochemistry professor at the Chinese University.

A World Health Organisation official said this week some of the affected children in China, most of whom are believed to be under the age of three, have "crystals" in their kidneys. Some might need surgery to avoid potentially deadly kidney failure.

In Hong Kong, parents have thronged public clinics to get their children tested for melamine by laboratories that analyse urine samples with sophisticated spectrometers.

Permanent liver damage can be caused when crystals suddenly form into large numbers of tubules in the kidneys of children that have consumed melamine, causing chronic kidney failure and requiring dialysis and even kidney transplants later on in life.