Overall, climate change is likely to increase human exposure to agricultural contaminants in the United Kingdom. The magnitude of the increases will be highly dependent on the contaminant type. The risks of many pathogens and particulate and particle-associate contaminants to human health could therefore increase significantly. These increases predicted in the U.K. agricultural environment can, however, be managed for the most part through targeted research and policy changes.
The sources of chemicals and pathogens of agricultural origin are likely to vary in the future because of climate and nonclimate factors. The potential for source variance arising from behavioral responses (e.g., intensification of management and altered patterns of chemical and manure use) will also be a compounding factor affecting the contaminant sources. Climate change is anticipated to fuel increased use of pesticides and biocides as farming practices intensify. Intensification may also lead to increased levels of occupational contact, increasing potential for zoonoses. Extreme weather events will mobilize contaminants from soils and fecal matter, potentially increasing their bioavailability.
Climate change will also affect the fate and transport of pathogens and chemical contaminants in agricultural systems. Increases in temperature and changes in moisture content are likely to reduce the persistence of chemicals and pathogens, whereas changes in hydrologic characteristics are likely to increase the potential for contaminants to be transported to water supplies. Models are available for predicting the effect of climate change on many selected pathways and processes, although models for certain transport routes (e.g., flood immersion and dust transport) may need developing or transferring from other sectors.
Overall, we anticipate that climate change will result in an increase in risks of pathogens and chemicals from agriculture to human health. As the current links between agricultural exposure and human health are unclear, it is not possible to estimate the magnitude of these changes or to conclude whether these increases in exposure are acceptable or unacceptable in terms of health end points. For chemicals, we believe that it is possible to manage many of these risk increases through better regulation, monitoring, and the development of a long-term research program. It is more difficult to predict the inputs and behavior of biological contaminants, so these may be more difficult to control than chemical substances. There are many major knowledge gaps and uncertainties, and we advocate that future work focuses on the following:
- The development of targeted surveillance schemes for presence and health effects of pathogens and chemicals arising from agriculture. This could include generation of quantitative microbial data in the environment (including nonculturable microorganisms), information on the presence and transport of anti biotic resistance genes, and data on occurrence of algal blooms and associate toxins.
- The development of future scenarios of land-use, social, technological, and economic change in order to assess how inputs of chemicals and pathogens may change into the future. Given the potential contribution of imported food as a source of disease burden and issues of traceability back to food processing, imported goods should also be considered.
- Generation of experimental data sets and models for exposure pathways (e.g., flood immersion, dust transport in air, post-application volatilization) that as yet have not been studied in any detail. Models for some of these exposure pathways already exist in other sectors, and these may be easily adapted to the agricultural systems. This work should include the development of an improved understanding of the uncertainties and limitations of climate scenario data for future agricultural contaminant fate.
- Refinement of regulatory models and procedures in light of new knowledge and existing risk assessments for contaminants need to be regularly updated.
This work should involve U.K. government departments and monitoring agencies (e.g., the Health Protection Agency, the Environment Agency, and Research Councils). A suggested timeline for these recommendations is provided in .
Possible time lines and strategy for research, surveillance, and risk mitigation for the predicted increases in human exposure to biological and chemical contaminants from agriculture.
The relationship between chemical and biological contaminants of agricultural origin and the health of the population is complex. The complexity of the relationship is increased by the projected variability of climate and extreme weather events anticipated under the climate change scenarios. Future studies into the risks of agricultural contaminants to health should therefore be multidisciplinary and pull together expertise in epidemiology, toxicology, land use, environmental chemistry, economics, and social science. Finally, it is important to recognize that agricultural systems are linked to the wider environment, and the implications of changes in inputs to and from these must not be ignored.