finding 13.3 : key-message-13-3

The frequency and severity of allergic illnesses, including asthma and hay fever, are likely to increase as a result of a changing climate. Earlier spring arrival, warmer temperatures, changes in precipitation, and higher carbon dioxide concentrations can increase exposure to airborne pollen allergens. (Likely, High Confidence)



This finding is from chapter 13 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

Due to limited resources and requirements imposed by the Federal Advisory Committee Act, the decision was made that this chapter would be developed using an all-federal author team. The author team was selected based on expertise in climate change impacts on air quality; several of the chapter authors were authors of the “Air Quality Impacts” chapter of the U.S. Global Change Research Program’s (USGCRP) Climate and Health Assessment.5ec155e5-8b77-438f-afa9-fbcac4d27690 This chapter was developed through technical discussions of relevant evidence and expert deliberation by the report authors via weekly teleconferences and email exchanges. The authors considered inputs and comments submitted by the public; the National Academies of Sciences, Engineering, and Medicine; and federal agencies.


Description of evidence base:

Considerable evidence supports the conclusion that climate change and rising levels of CO2 affect key aspects of aeroallergen biology, including the production, temporal distribution, and potential allergenicity of aeroallergens.14835bc7-3df6-4fac-9e9a-2863c09e800a b7869aef-b3cd-40c5-9efd-588abf7af927 c60ed28e-5ec3-4b9b-8b41-c6c29e4fda70 f89543d6-09bf-436c-8f7e-c0f908473457 b95e5f99-5555-476e-a026-09597b43f8be This evidence includes historical trends indicating that climate change has altered seasonal exposure times for allergenic pollen.1c917926-3eba-452b-bd2b-f9e88b374312 These changes in exposure times are associated with rising CO2 levels, higher temperatures, changes in precipitation (which can extend the start or duration of pollen release times), and the amount of pollen released, the allergenicity of the pollen, and the spatial distribution of that pollen.1bc9d76c-14c8-4245-9ccb-1355cdc48d0b be4c7d95-2b71-45fb-b901-b68f5c1ad057 2d1ffd71-6c31-4d2e-9867-bdf330be45c1 025515fc-f83a-47ff-b547-92ade9513c15

Specific changes in weather patterns or extremes are also likely to contribute to the exacerbation of allergy symptoms. For example, thunderstorms can induce spikes in aeroallergen concentrations and increase the incidence and severity of asthma and other allergic disease.713cd919-826b-426d-bf51-761a58ec7f22 471472b2-1c16-40db-99e2-b529ab7e417b However, the specific mechanism for intensification of weather and allergic disease is not entirely understood.

Overall, climate change and rising CO2 levels are likely to increase exposure to aeroallergens and contribute to the severity and prevalence of allergic disease, including asthma.971ee908-7da0-416e-8b6c-a72984d129ba There is consistent and compelling evidence that exposure to aeroallergens poses a significant health risk in regard to the occurrence of asthma, hay fever, sinusitis, conjunctivitis, hives, and anaphylaxis.036ba27d-8341-4f6d-ad66-1288e53dee65 12159d43-9762-4788-9a10-8e0ad5ab4d9a 8e7c1bc6-33dc-479d-a0d7-0d8c90f647bf b1d1a01e-78e1-4b26-a8b4-513c43a7240c Finally, there is evidence that synergies between aeroallergens and air pollution, especially particulate matter, may increase health risks for individuals who are simultaneously exposed.7a9fde66-dbc1-4152-bd11-2d68d4e7d66a f978dc0e-2a56-4bc9-9c67-d2f2a1de0914 3eabd82a-4bf8-4a43-9716-a019a02d9d8d

New information and remaining uncertainties:

While specific climate- and/or CO2-induced links to aeroallergen biology are evident, allergic diseases develop in response to complex and multiple interactions, including genetic and nongenetic factors, a developing immune system, environmental exposures (such as ambient air pollution or weather conditions), and socioeconomic and demographic factors. Overall, the role of these factors in eliciting a health response has not been entirely elucidated. However, recent evidence suggests that climate change and aeroallergens are having a discernible impact on public health.c9c2ea5f-223f-4594-b182-40b473c6e665 4beaa115-1cbe-404e-a62d-4a943c946820

There are a number of areas where additional information is needed, including regional variation in climate and aeroallergen production; specific links between aeroallergens and related diseases, particularly asthma; the need for standardized approaches to determine exposure times and pollen concentration; and uncertainty regarding the role of CO2 on allergenicity.

Assessment of confidence based on evidence:

The scientific literature shows that there is high confidence that changes in climate, including rising temperatures and altered precipitation patterns as well as rising levels of atmospheric CO2, will increase the concentration, allergenicity, season length, and spatial distribution of a number of aeroallergens. These changes in aeroallergen exposure are, in turn, likely to impact allergic disease.

References :

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