PhD Defence: Associations of Residential Exposure to Pesticides and Cleaning Agents with Asthma and Related Symptoms

Summary dissertation

Evidence suggests that the prevalence of asthma and allergic symptoms have risen rapidly over the past decades. It has been suggested that occupational exposure to pesticides is associated with an increased risk of asthma and related respiratory symptoms in adults. There is also the suggestion that adults who use cleaning agents professionally or in the home have an increased risk of asthma and related respiratory symptoms. In addition, there is increasing concern that some cleaning agents being used in households might be associated with an increased risk of asthma and allergic symptoms in children. However, the current evidence on the effect of exposure to pesticides and cleaning products among children and adolescents is limited. 
In Chapter 2, It was found that a small proportion of the study participants lived near (i.e., within 50 or 100 m) agricultural fields with the selected crops relevant for pesticide use (approximately 7% of the population residing within the 100 m). The results indicated further that 40 and 64 percent of the PIAMA participants lived within 500 and 1,000m buffers, respectively. It was hypothesised that participants who lived within 500 and 1,000m buffers tended to have minimal pesticide exposure compared to participants who lived within 50 and 100 m. 
Chapter 3 examined whether living close to crops that are likely treated with pesticides is associated with asthma and related respiratory symptoms among PIAMA participants at the time of 14 years of follow-up. However, we found no evidence that living close to agricultural fields assumed to have been treated with pesticides is associated with an increased risk of asthma and related respiratory symptoms. 
In Chapter 4, it was found that the use of cleaning agents in the household was not associated with increased risks of asthma, rhinitis, and eczema in adolescents who participated in the PIAMA study at the time of 14 years of follow-up. 
Chapter 5 presents the opportunity for the development of studies investigating the effects of environmental exposure to pesticides on the development of asthma and related respiratory symptoms in children. However, this Chapter cannot provide a comprehensive review of the effects of pesticide exposure on human health in Tanzania due to limited data and literature on the subject.  
This thesis set out to investigate the effects of environmental exposure to pesticides and cleaning agents on the prevalence of asthma and allergic symptoms in adolescents who participated in the PIAMA. We observed no association between these environmental factors (environmental exposure to pesticides and cleaning agents) and the risk of asthma, related respiratory symptoms, and allergic symptoms in adolescents. There is a need to develop a birth cohort study that will investigate the influence of environmental exposure to pesticides and the use of cleaning agents on the development of asthma, allergic symptoms and lung function in children in developing countries.