Risk factors of fly breeding in household food waste collection bins after waste sorting in Fengxian District, Shanghai

Background The Regulations on the Management of Domestic Waste in Shanghai has been implemented in Shanghai since July 1th, 2019, which classifies domestic waste as recyclable waste, hazardous waste, household food waste, and residual waste. Household food waste collection bins are an important place for fly breeding.

Objective The purpose of this study is to investigate fly breeding and its risk factors in household food waste collection bins in residential areas in Fengxian District, Shanghai, and to provide evidence for controlling the density of flies in residential areas and improving waste sorting policies.

Methods The breeding rate of fly larvae and infestation rate of adult flies in household food waste bins were estimated in Fengxian District of Shanghai from August 6th to 28th, 2019, following the fly larva visual inspection method and adult fly visual inspection method of the Vector density monitoring method Flies (GB/T 23796-2009). Type of residential areas, adult flies effectively isolated by bin lips, any residuals left, household food waste collection bins' placement, collection hours, sun shading, wash schedule, and involvement of volunteers and property management were recorded by trained investigators.

Results Among the 299 household food waste collection bins investigated, 16 were found fly larvae, and the breeding rate of fly larvae was 5.35%; 69 were found adult flies, and the infestation rate of adult flies was 23.08%. Residuals left in household food waste collection bins (OR=166.56, 95% CI:17.51-1584.59), household food waste collection bins not effectively isolating adult flies (OR=26.16, 95% CI:4.06-168.70), and no volunteer service (OR=15.50, 95% CI:1.32-182.44) were the risk factors for breeding of fly larvae; complexes of multi-storied or high-rise buildings (versus complexes of villas, OR=11.06, 95% CI:3.29-37.15), complexes of self-built houses in rural areas (versus complexes of villas, OR=10.45, 95% CI:2.85-38.53), residuals left in household food waste collection bins (OR=9.42, 95% CI:3.59-24.75), and household food waste collection bins not effectively isolating adult flies (OR=63.59, 95% CI:20.74-195.00) were the risk factors for the infestation of adult flies.

Conclusion Leaving residuals in household food waste collection bins and not effectively isolating adult flies are the risk factors for fly breeding in household food waste collection bins in residential areas. It is important to train property managers and volunteers on waste sorting, so as to reduce the fly breeding rate.