PUB, the national water agency, thanks Mr Lee Chee Chee for his letter ("How is water supply being kept safe?"; Forum Online, Sept 2).

The pesticides used for fogging have undergone the World Health Organisation (WHO) Pesticide Evaluation Scheme and have been certified safe and suitable for public health use.

The concentration used in fogging strictly follows the manufacturer's recommendations and is safe for the environment.

PUB monitors raw water in our reservoirs closely, and from our monitoring data, we have not detected these pesticides in the raw water.

Furthermore, raw water from the reservoir is first treated at the waterworks to WHO drinking water quality guidelines before it is supplied to households.

PUB welcomes public feedback and members of the public can call the PUB 24-hour call centre at 1800-2255 782 (1800-Call PUB) or e-mail PUB_One@pub.gov.sg

Lim Mong Hoo

Chief Specialist (Water Quality)

PUB, The National Water Agency