Review Methods to Address Issues in Environmental Health Epidemiology

The advent of evidence-based practice in health has led to widespread acceptance of reviews in clinical and healthcare fields. Similarly, review methods in environmental epidemiology offer a unique opportunity of collating and analyzing highly heterogenous data, i.e., human and animal data, for unbiased decision making. Thus, this dissertation focuses on the use of systematic review and scoping review (a type of systematic review) methods to understand specific issues in environmental health.

The aims of this dissertation were to investigate: (i) the associations between chemical nutrients/contaminants, temperature, and harmful algal blooms due to Karenia brevis in the North American region; (ii) the environmental effects of a novel insecticide, cycloxaprid (CYC), on target and non-target insect species; and (iii) the effect of land use, land cover, and climate change on incidence of Japanese Encephalitis (JE) disease among Asian populations.

We performed a scoping review of the existing literature to get an overview of the scientific advancements and status quo of emerging evidence related to the associations between temperature, chemical nutrient/contaminants, and K. brevis blooms. We recommended increasing the availability and accessibility of contaminants data in aquatic systems and enhancing contaminant data coverage to account suggestive shift in the distribution of K. brevis blooms.

Further, we aimed to find answers to specific questions related to JE infection and CYC. Our objective was to identify and retrieve international research, assess the quality of evidence to confirm if the current knowledge is based on relevant evidence, and to address any uncertainties or conflicting evidence to draw meaningful conclusions for future research and unbiased decision making. Findings of the CYC systematic review suggested conducting additional research to clarify the mechanism of action of cycloxaprid and its metabolites on target and non-target insect species. The findings from the JE systematic review suggested that future research must focus on conducting high-quality ecological and individual-level studies.

In conclusion, use of systematic and scoping review methods unveils the quality of evidence and informs future environmental health research.