Assessing a drop box programme: A spatial analysis of discarded needles

Abstract

Background Distributing sterile injection equipment to injection drug users is one of few proven ways of lowering the transmission rate of blood borne viruses. Distribution of equipment has also been linked to increased needle discarding, which is a public health risk for both injectors and their host communities. Drop boxes (anonymous and public-access sharps containers) are a promising and increasingly popular means of reducing unsafe disposal, yet there is little empirical research to support or guide their implementation. Methods Using a dataset containing the locations of 7274 discarded needles and syringes collected monthly in the non-park open spaces of a 2.5 km 2 neighbourhood of Montréal, Canada for a period of five years, we compared levels of discards before and after the installation of 12 drop boxes. We used quasi-Poisson regression to test the effects of drop boxes on monthly counts of collected discards for areas within a walking distance of 25, 50, 100 and 200 m of a drop box. We adjusted for known time-dependent covariates linearly and unknown time-dependent covariates using a smoothing function. Results We found strong evidence of reduced discarding following the installation of drop boxes; drop boxes were associated with reductions of up to 98% (95% CI: 72–100%) and significant reductions for areas up to 200 m from a drop box. Reductions were inversely proportional to walking distance from drop boxes. No measure of weather or use of needle exchange programmes (NEPs) had a consistent relationship with discard counts. Conclusion Our research suggests that IDUs changed their needle-disposal behaviour in response to increased safe disposal options. In addition to being relatively low-threshold, economical and rapid, drop boxes appear to be a highly effective intervention to reduce discarded needles.