Chemical link to mass fish deaths?

The mass fish deaths in Bishan-Ang Mo Kio Park ("Mass fish deaths again at Bishan-Ang Mo Kio Park"; last Wednesday) are puzzling, although a fish expert from the National University of Singapore explained that the cause could have been low oxygen levels related to climate conditions.

I wonder why the effects of climate change should be so localised; they should also apply to other parts of the island and our neighbouring countries.

A similar incident, involving mass lobster deaths, occurred in the Bay of Fundy, between New Brunswick and Nova Scotia of Canada, and was reported in the media in 2010.

The deaths were eventually traced to the pesticide sprayed on farms and carried down by the river to the sea.

The active ingredient of the pesticide was cypermethrin, which is extremely toxic to fish.

Cypermethrin is also the active ingredient in the insecticide used in chemical fogging, which is widely and frequently carried out in Singapore to control the mosquito population.

Perhaps it is worthwhile for the authorities to look into this possibility in the mass fish deaths here.

Cypermethrin, besides being toxic to humans as a neurotoxin, is classified as a carcinogen or cancer-inducing agent.

It is also being investigated for its possible role in Parkinson's disease.

Ong Siew Chey (Dr)

A version of this article appeared in the print edition of The Straits Times on July 28, 2015, with the headline 'Chemical link to mass fish deaths?'. Print Edition | Subscribe