Agricultural interventions to reduce PM2.5 in the UK: impacts on health and the economy.

BACKGROUND: Exposure to particulate matter is linked to increased mortality, respiratory and cardiovascular diseases, including lung cancer, ischaemic heart disease and asthma, among other adverse health outcomes. Emissions of particulate matter from agriculture occur directly from farming activities and from reaction of ammonia with acidic pollutants to form fine particles (PM2.5: particles with diameter of 2.5 μm or less). In the United Kingdom, ammonia has slightly increased in recent years, in contrast to other PM2.5 sources. In addition, NH3 emissions can contribute to nitrogen deposition, which, in excess of critical thresholds, may result in biodiversity loss.

OBJECTIVES: Our objectives were to assess the effectiveness and cost-effectiveness of inter-related interventions to: (1) assess the annual health impacts of air pollution (PM2.5) from intensive livestock agriculture and farming on the general population; (2) valuate the effectiveness and cost-effectiveness of the specific interventions at the national level; (3) assess impacts on ecosystems; and (4) examine the extent to which rural residents are concerned about agriculture and their health.

DESIGN AND METHODS: We performed a health impact assessment based on PM2.5 exposures associated with three levels of agricultural intervention. We also performed an economic analysis, capturing valuation of health and productivity, and costs to the national health service, as well as an assessment of ecosystem impacts based on nitrogen deposition and biodiversity loss. A survey of rural residents' health was undertaken to investigate links between self-reported health and agriculture.

INTERVENTIONS: The three intervention scenarios comprised 19 individual mitigation actions at a farm level, each with differing uptake levels in low, medium and high scenarios.

MAIN OUTCOME MEASURES: The health impact assessment and economic analyses included all-cause mortality, and incidence of lung cancer, ischaemic heart disease, cerebrovascular disease, and childhood asthma incidence. The ecosystem analysis examined biodiversity loss, and the rural residents survey addressed respiratory, gastrointestinal, and neurological diseases.

RESULTS: Modest changes in PM2.5 concentrations across the United Kingdom associated with the low, medium and high intervention scenarios resulted in relatively small impacts compared to national baseline levels of mortality and morbidity (i.e. -0.01% to -0.05%). Overall, United Kingdom-wide avoided costs ranged from £78.1 to £93.4M, with much lower annual avoided costs to the national health service. All habitats had a relative increase in biodiversity under all scenarios with expected benefits of £3.4-4M. There were 450-500 respondents in each of the 2 waves of the rural resident surveys. No associations were identified between any self-reported disease occurrence and farm-related variables.

LIMITATIONS: Our approach used several different models, requiring important assumptions and uncertainties. Respondents to the residents' survey tended to be aged over 45 and female and findings are applicable primarily to this demographic.

CONCLUSIONS: Based on the modest modelled changes in PM2.5 concentrations associated with the intervention scenarios, we estimated small impacts with human health, as well as economic and ecosystem effects. We found no evidence of self-reported health issues in relation to farms or farming practices.

FUTURE WORK: Impacts from alternative farming interventions should be assessed to maximise PM2.5 reductions in the United Kingdom.

FUNDING: This article presents independent research funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme as award number NIHR129449.