Pesticide Exposure and Suicidal Ideation in Rural Communities in Zhejiang Province, China/Exposition Aux Pesticides et Idees Suicidaires Dans Les Communautes Rurales De la Province Du Zhejiang En Chine/Exposicion a Plaguicidas E Ideas Suicidas En Comunidades Rurales De la Provincia De Zhejiang, China (2009)

Introduction The use and availability of pesticides are significant concerns in the field of mental health, not only because these chemicals are used in suicide attempts (1) but also because their possession may be directly associated with mental disorder. Suicide rates are reported to be higher in areas where organophosphates are used (2) and exposure is a possible risk factor for Parkinson disease (3,4) and Alzheimer disease, (3) for depressive and anxiety disorders (5,6) and for mortality ascribed to mental disorder. (7) However, research in this area remains controversial. (8,9) Pesticides have been widely used in agriculture since the 1950s (10) but, despite precautionary measures, intentional and occupational poisoning remain major concerns. For example, pesticide ingestion was implicated in 62% of suicides in China between 1996 and 2000, which corresponds to around 175 000 cases per year. (1,11) Suicide in China accounts for 44% of all suicides worldwide. (12) Moreover, suicide is the fifth leading cause of death in China (13) overall and the leading cause in 15-34-year-olds. (14) In rural areas, suicide rates are 2-5 times those in urban areas (13, 15) and, in contrast to Western populations, the rate is higher in women than men. (13) Although mental disorder, especially depression, is associated with suicide, (16) the link between suicide and mental disorder may be relatively weak in China. (13) The reasons for the high rate and unique pattern of suicide in China have yet to be established. Organophosphate pesticides are used widely in China and the potential for exposure is high. Despite this, the mental health risks of prolonged exposure remain unclear. We investigated the association between the storage of pesticides at home and recent suicidal ideation in rural China by analysing data from a province-wide survey of mental disorders that was carried out in 2001 as part of a WHO and Chinese Ministry of Health project. Methods The study was performed in Zhejiang province, a densely populated coastal province of China that in 2000 had a total population of 45 million, 70% of which lived in rural areas. It is one of the most developed provinces in China and in 2000 had an average per capita gross domestic product (GDP) of 13 461 renminbi (US$ 1660), the fourth highest among Chinas 31 provinces and independent municipalities. Sample size The survey was designed to ascertain a prevalence of mental disorder of 15% with 1% precision. In addition, the sample size was increased to 15 000 to enable comparisons to be made according to gender and urban or rural residence. The ratio of urban to rural residence was estimated to be 1:2. (17) Sampling procedure The survey employed a multistage sampling process that has previously been described in detail by Shi et al. (18) The sampling frame was the province-wide computerized household registry, which was updated during the 2000 national census. Seven indicators (i.e. population density, birth rate, the proportion of non-agricultural labourers, per capita GDP, illiteracy rate, crude death rate and proportion aged > 65 years) for 11 cities and 63 rural counties were subjected to a principal components factor analysis. Two factors accounted for 65.2% of the variance. The factor scores were then used to construct five strata: (i) 5 cities (comprising 45.5% of the total urban population); (ii) 6 cities (comprising 54.5% of the total urban population); (iii) 19 counties (comprising 30.2% of the total rural population); (iv) 13 counties (comprising 20.6% of the total rural population); and (v) 31 counties (comprising 49.2% of the total rural population). This analysis considered only the three rural strata, which broadly corresponded to mountain, plains and coastal regions. Groups of three, two and five counties were selected from the three rural strata (mountain, plains and coastal regions, respectively) by sampling in proportion to the population aged 15 years or over. …