PUB, the national water agency, thanks Mr Lee Chiu San for his feedback ("Outdoor fogging ineffective, hurts wildlife"; Forum Online, Dec 22).

The fogging at Lorong Halus Wetland is carried out by PUB to keep the midge population in check.

While midges are part of the aquatic ecosystem and do not bite, or carry or spread diseases, we have carried out fogging to minimise the nuisance that a mass emergence of midges brings to park users and residents.

Fogging is currently conducted twice weekly. We will monitor and step down on the fogging frequency if the midge situation improves.

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

The concentration used in fogging is carefully controlled to be at its lowest effective dosage to minimise risks to the environment.

The pesticides can also be effectively removed during the water treatment process.

PUB monitors raw water in our reservoirs closely and the raw water is treated at the waterworks to WHO drinking water quality guidelines before it is supplied to households.

Nevertheless, members of the public who are sensitive to fogging may wish to avoid close proximity during fogging operations.

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

Ridzuan Ismail

Director

Catchment and Waterways Department

PUB