Impacts of nitrogen deposition in the natural environment on pollen allergy and respiratory infection outcomes in Belgium

Allergic disorders related to pollen exposure are associated with an important burden of disease because of their high prevalence, often life-long morbidity impact, and their role in increasing the susceptibility to respiratory viral infections. Therefore, aeroallergen exposure is a major public health concern. The prevalence of allergies to aeroallergens is increasing due to various interactions between changes in the environment, including air pollution and climate warming, and lifestyle. One of the possible, yet underexplored, additional drivers of increasing aeroallergen and allergy prevalence is nitrogen deposition. Excessive environmental nitrogen enrichment through fossil fuel combustion and intensive agriculture is altering plant and pollen distributions and abundances, the timing, duration, and intensity of pollen seasons and potentially the allergenic properties of pollen grains. These combined changes are expected to have multiple impacts on the prevalence and severity of allergic diseases and potentially respiratory infections. NITROPOL-BE’s main objective is to understand how nitrogen deposition affects pollen allergy burden in Belgium, adjusting for potential confounding by air pollution and climate. First, we will examine the effects of nitrogen enrichment and induced plant community shifts on pollen abundance, species composition, and pollen potency by setting up a monitoring scheme in natural environments across a nation-wide nitrogen enrichment gradient. Second, we aim to experimentally test the hypothesis that nitrogen enrichment induces increased potency of airborne pollen through quantifying pollen allergens and clinically testing allergen potency of pollen of allergenic grass and tree species collected in natural environments and from plants subjected to experimental nitrogen enrichment. Finally, we aim to explore the burden of allergic and respiratory disease including the recent COVID19 outbreak attributable to nitrogen deposition and aeroallergen exposure and to evaluate health care costs and benefits under a range of nitrogen deposition scenarios and policy interventions through a disability-adjusted life-year (DALY) approach. NITROPOL-BE will engage a multidisciplinary team of scientists, biodiversity conservationists, policymakers, and citizens (allergy patients) in Belgium. It aims to provide the scientific basis and evidence to support regional nitrogen deposition reduction and environmental policies as well as national health policies.