Impact of a national ban on highly hazardous pesticides on suicide and agricultural productivity in Nepal

Pesticide self-poisoning is a major contributor to suicide in low- and middle-income countries. Between 2019 and 2021, Nepal banned several highly hazardous pesticides and replaced high-concentration aluminium phosphide tablets (3 g 56%) with products of alternative formulations and lower concentration. This study examines the impact of these regulations on pesticide suicides and agricultural productivity. National data on pesticide suicides (April 2017–August 2024) were obtained from two forensic toxicology laboratories. Pesticides were grouped into categories. Logistic regression estimated odds ratios (ORs) for changes in pesticide involvement between the pre-ban (April 2017–February 2020) and post-ban (September 2021–August 2024) periods. Post-ban provincial variation in pesticide suicides was assessed using age-standardised rates and standardised mortality ratios (SMRs). Joinpoint regression was used to assess trends in crop yields (2005–2023). A total of 3,005 and 1,331 pesticide suicides were analysed in pre- and post-ban periods, respectively. The mean monthly number of identified pesticide suicides declined by 56.9% (85.9 to 37.0). The proportions of pesticide suicides involving the categories of organophosphorus pesticides, carbamates, and organochlorines, including banned pesticides such as dichlorvos and triazophos, decreased. In contrast, phosphine gas-generating pesticides increased proportionally (31.1% to 48.2%), largely driven by aluminium phosphide. Post-ban suicides were more common amongst males (56.0%), individuals aged 15–44 years (52.8%), and in Bagmati and Lumbini Provinces (SMRs = 1.26 and 1.35) than their counterparts. No adverse changes in rice, pulse, or vegetable yields were observed. Nepal’s 2019–2021 pesticide regulations were associated with reduced involvement of banned organophosphorus pesticides, carbamates, and organochlorines. However, continued aluminium phosphide deaths warrant surveillance and further regulatory action. Our findings were similar compared to previous studies monitoring pesticide exposures after a ban. There are potential policy implications from this study. In Nepal, the 2019–2021 bans were followed by fewer suicides involving banned pesticides without declines in major crop yields, but aluminium phosphide remained prominent after regulation.