Measured and modelled environmental exposure of residents to pesticides

Abstract

Most people, if not all, will be exposed at least once in their life-time to a certain level of pesticide(s). For non-occupationally exposed groups, a great portion of this exposure can be attributed to dietary intake and the remaining to environmental exposure. In the Netherlands, the application of pesticides on agricultural fields has raised concerns from residents living close to these. In order to understand if a certain disease is related to an exposure to any given chemical, we first need to identify the exposed vs non-exposed population and also understand the levels, duration and frequency of exposure. The aim of my thesis is on investigating residents’ environmental exposure to pesticides by studying drivers of this exposure as well as temporal and spatial variability in different pesticides concentration. Chapter 2 details the methodology used to study residential exposure to pesticides and a list of (practical) lessons learned. Chapter 3 described the spatial and temporal variation of 46 different pesticide concentrations in air outside and inside homes. Here, we saw that most pesticide concentrations were 5–10 times higher in outdoor air during the spraying period when comparing with the non-spraying period. Concentrations were overall higher closer to the fields (<250 m) then further away. Environmental exposure to pesticides via air may occur year-round. Chapter 4 focused on the indoor dust matrix. House dust that was collected from vacuuming floors (VFD) and from newly placed clean doormats (DDM). Pesticides were found in indoor dust of all homes included in our study and we found that people living close to fields were exposed year-round to pesticides in house dust. Chapter 5 studied personal exposure in the residential setting. Handwipes and urine samples were collected in parallel. Concentrations in hand wipes were overall higher during the spraying period when compared to the non-spraying period and higher in farmer families compared to non-farmer families. Chapters 6 developed a deterministic model framework (OBOmod) to assess exposure of residents living near fields. This framework describes levels in the environment from the moment pesticides are sprayed until they end up in the air and house dust. The model evaluation shows that, for most model outputs, the framework can be used in support of i) health and epidemiological studies, and ii) regulations and policy making. Chapters 7 reviewed the findings from each chapter and discussed on new evidence, comparison with previous works and future research paths. My recommendation for further improving residential exposure assessment to pesticides can be summarized in four points: 1) Perform research in areas where sideways or upward spraying techniques are used; 2) Focus more on pesticide levels in house dust, as it can be especially important in exposure of more vulnerable populations, like toddlers; 3) Improve the modelling framework, by means of more verification and making it accessible to all; 4) Studies on mixtures in relation to possible adverse health effects are needed. Particularly, for pesticides with the same mode of action and frequently detected in our samples.