Photo by Alex Jones on Unsplash
Photo by Alex Jones on Unsplash

Is nitrogen fertiliser supercharging allergy-causing pollen?

Embargoed until: Publicly released:
Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Observational study: A study in which the subject is observed to see if there is a relationship between two or more things (eg: the consumption of diet drinks and obesity). Observational studies cannot prove that one thing causes another, only that they are linked.

Cells: This is a study based on research in micro-organisms, cells, tissue, organs or non-human embryos.

Nitrogen-fertilised grasslands may produce six times more pollen than their unfertilised counterparts, according to international researchers, who compared pollen samples from 25 nitrogen-fertilised and 25 non-fertilised grasslands in Belgium. The study found an average pollen count of 3.6 mg/m2 for the fertilised grasslands - 6.2 times higher than the unfertilised grasslands with 0.6 mg/m2 of pollen. They also tested if the pollens were more likely to cause allergic responses from people. They found that immune cells in the blood of 20 people were more sensitive to nitrogen-fertilised pollen than non-nitrogen-fertilised pollen.

Journal/conference: Lancet Planet Health

Organisation/s: Allergy and Clinical Immunology Research Group, KU Leuven, Belgium

Funder: The NITROPOL-BE project (B2/212/P1/NITROPOL-BE), was funded by the Belgian Science Policy Office in the framework of Belgian Research Action through Interdisciplinary Networks (BRAIN-be 2.0). RS and LVG are supported by a Fonds Wetenschappelijk Onderzoek senior clinical investigator fellowship (1805523N and 18B2222N, respectively).

Media release

From: The Lancet

Peer-reviewed / Observational + Experimental study / Plants + Cells

The Lancet Planetary Health: Pollen from grassland with nitrogen fertiliser may be more likely to trigger hay fever than pollen from unfertilised grasslands, study suggestsNitrogen fertilised grasslands may produce six times more pollen than their unfertilised counterparts, suggests a study published in The Lancet Planetary Health journal. The study also suggests pollen from fertilised grasslands is more likely to trigger hay fever than pollen from unfertilised grasslands.

Over recent decades, the rate of pollen allergies has increased globally. One reason for this rise is thought to be atmospheric nitrogen pollutants affecting pollen and leading to an increased release of allergens; however little research has looked at the impact of nitrogen fertilisers, a major source of environmental pollution, on pollen.

This study compared pollen samples from 25 nitrogen-fertilised and 25 non-fertilised grasslands in Belgium. The study found an average pollen count of 3.6 mg/m2 for the fertilised grasslands - 6.2 times higher than the unfertilised grasslands with 0.6 mg/m2 of pollen.

The study also looked at how allergenic the pollen was by taking the blood of 20 people and exposing it to the pollen from the two types of grassland. When comparing the sensitivity of the participant’s immune cells (basophils), they found on average that they were five times more sensitive to the pollen from the fertilised grasslands than the unfertilised grassland. The authors say to confirm the allergy response further research should expose participants themselves to pollen and then study their immune response.

Authors say this study is the first to suggest a clear relationship between nitrogen fertiliser and pollen count and its ability to trigger allergies and that the findings highlight an urgent need for strategies to not only address nitrogen fertiliser’s impact on biodiversity and the environmental, but also the human health impact posed by nitrogen pollution.

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