Is climate change affecting hay fever and pollen counts?

A study published in the Proceedings of the National Academy of Sciences February 2021 has shown that the last 30 years have resulted in ever-rising pollen counts and longer pollen seasons in the USA.

The higher the Pollen Count (the number of pollen grains per cubic metre of air), the greater the number of children and adults affected by Allergic Rhinitis (or ‘hay fever’). Whilst this study did not under take a population-based assessment of the burden of pollen-associated disease, the authors used long-term pollen data from 60 North American stations from 1990 to 2018, spanning 821 site-years of data to assess the fluctuations in Pollen Counts. They used Earth system model simulations to quantify the role of human-caused climate change in continental patterns.

The study showed widespread advances and lengthening of pollen seasons (+20 days) and increases in pollen concentrations (+21%) across North America, which are strongly coupled to observed warming. Human forcing of the climate system contributed ∼50% of the trend in pollen seasons and ∼8% of the trend in pollen concentrations. They conclude that anthropogenic climate change has already exacerbated pollen seasons in the past three decades.

The impact of this study is two-fold;

  • The last 30 years of data gives insight into rising pollen counts correlating with anthropogenic climate dynamics
  • There is a need for long term data monitoring of pollen-associated-disease prevalence, economic and health impact

Primarily, this study suggests documents a longterm trend in the prevalence exposure of pollens in the USA.

Questions are also raised about whether climate alone influences these statistics, or whether land-use, drainage, agriculture and patterns of urbanisation may also result in these trends.

It cannot prove that the prevalence of allergic rhinitis or allergic asthma has also increased, or any of the suggested likely impacts of this condition, such as interaction between viral disorders and pollen count exacerbations, A&E attendance figures, economic impacts, school attendance, cognitive and physical performance.

Nonetheless, these figures are a stark reminder about how many moving parts are potentially impacting upon the health of ourselves and our children as they grow.

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