THE 17 per cent jump in the number of cancer cases since 2010 cannot be regarded as a matter of course ("Sharp rise in number diagnosed with cancer"; June 21).

It cannot be explained on the basis of the ageing of our population.

We must look for extraneous causes.

For example, there was a village in China where a large number of residents suffered from cancer of the oesophagus. This was traced to the preserved, seasoned vegetables the villagers regularly consumed.

The village chickens picked up scraps of food from the ground and also developed the disease.

During the Vietnam War, the Americans used Agent Orange to defoliate the forests. Many of those who came into contact with the chemical developed leukaemia and lymphoma.

We import practically all our food; insecticides and other harmful chemicals in them may escape detection during random checking.

Regular chemical fogging is also carried out here by some households. The active ingredient, cypermethrin, is a neurotoxin classified as a possible human carcinogen, or cancer-inducing substance.

Cypermethrin can remain in the environment for up to three months. It is quite soluble and may bind to soil particles to contaminate the groundwater.

There are probably many other possible extrinsic carcinogenic factors existing in our environment that we are not aware of.

It is up to us to be vigilant and try to discover some of these harmful environmental factors.

Ong Siew Chey (Dr)