Most mosquito-breeding spots are found in homes and not at construction sites.
This makes the job of detecting breeding spots harder because, unlike entering construction sites, the authorities cannot go into homes easily or frequently to check on them, said Minister for the Environment and Water Resources Masagos Zulkifli yesterday.
"This is why we have to emphasise repeatedly that every household must constantly do the necessary ground actions to remove potential breeding spots in their own homes," he said.
Mr Masagos was giving Parliament an update on mosquito control efforts in the light of the Zika outbreak last month.
He said the National Environment Agency did 748,000 inspections between January and July - 638,000 of them in homes and 4,400 at construction sites.
Half of the 10,000 or so mosquito-breeding habitats found were in homes, while only 5 per cent were at construction sites, he said in his reply to Dr Tan Wu Meng (Jurong GRC), Ms Foo Mee Har (West Coast GRC) and Non-Constituency MPs Dennis Tan and Daniel Goh.
Mr Masagos also said the authorities have stepped up enforcement action against errant contractors.
For instance, construction sites exceeding $50 million in project value have to employ full-time environmental control officers, while those with sites valued between $10 million and $50 million must employ such part-time officers.
The authorities have also issued stop-work orders and prosecuted repeat offenders in court.
"This combination of measures... has helped bring about a significant reduction in the percentage of inspected construction sites found with mosquito breeding - from 30 per cent in the 1990s to 11 per cent in 2013 to about 9 per cent today," Mr Masagos said.
He added that, between January and July, 2,200 households were fined after inspectors found breeding spots in their homes.
"Whether it is a home or a construction site, we must be as vigilant," Mr Masagos said.
"Everyone must do their part to make sure they do the five-step mozzie wipeout as a daily habit, to ensure that they don't give the mosquitoes a chance to breed."