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Trouble In The Air: Warmer Temperatures Lengthen Midwest Ragweed Pollen Season

Kim Knowlton

Posted February 21, 2011

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Spring is just around the corner, even if I can see snowflakes falling today. As part of the annual Rite of Spring, I’ll be calling my physician to get allergy medicine lined up. For me -- as for 36 million other Americans with seasonal allergies - -the approach of warmer weather means (along with daffodils) there’ll soon be spring pollen to deal with.

But a new study just released in the journal the Proceedings of the National Academy of Sciences (PNAS) suggests something more troubling in the air: Warmer weather in the last 15 years has already made autumn ragweed pollen seasons longer --by as much as 13 to 27 days in a swath of Midwestern states from Texas northward into Canada. Ragweed is one of the worst allergic plant offenders- it’s the #1 cause of fall allergies

I was among the co-authors on the new PNAS study, along with other university researchers and experts from national laboratories. It’s the first time anyone’s been able to pull together enough recent pollen data from a wide area to show that rising temperatures are already affecting pollen season length.

We knew already that springtime was coming 10 to 14 days earlier than it did 20 years ago. But this new work measures the length of the ragweed pollen season in the US for the first time, and finds it's getting longer as temperatures rise, especially the farther north you go. (States like Minnesota and Wisconsin showed some of the strongest effects.) If these warming trends continue (as they’re projected to) under a changing climate, the health of people with severe allergies or asthma could really suffer.

For me, watery, itchy eyes, a runny nose, sneezing and congestion, is a treatable nuisance, though it makes my workdays less productive. However, for an estimated 23 million Americans with asthma (including 7 million kids), about 70% of whom also have allergies, pollen season can be a severe health threat, since pollen can trigger asthma attacks. Allergies & allergy-driven asthma already cost the US $32 billion annually.

I worked on a 2007 NRDC report that looked at second way that a changing climate can impact pollen, air pollution and health. Carbon dioxide, or CO2, makes ragweed and other plants grow lusher, larger, and produce more pollen. Rising temperatures also worsen concentrations of ground-level ozone smog. More than 110 million Americans live in areas where late summer means both unhealthy smog & ragweed pollen. I’ve blogged on this before.

So in the face of longer, more intense airborne pollen and pollution seasons, what are we to do? There are definitely positive steps we can take:

  • Check out daily, local pollen and air pollution conditions if you or a family member is allergic or has asthma. EPA’s AirNow website and the National Allergy Bureau both provide info.
  • Change your clothing after spending time outdoors, and wash your hair and bedding to minimize your time in close contact with pollen.
  • Beyond these and other steps to reduce individual exposures, we need an expanded monitoring network of pollen sample collection sites; more meteorological data stations; systems to gather information on pollen’s local health effects; and more information on carbon pollution emissions sources, too, to better understand their interconnections.

The ways that climate change is impacting the nation’s health are coming into sharper focus. We need to keep our federal agencies’ climate change program funding, and strengthen environmental/health monitoring networks, to help our most vulnerable communities design and implement effective ways to respond to a changing climate.

Is there anything more important to invest in than health?

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KN SmithFeb 22 2011 11:34 PM

This is really interesting research that should be getting a lot more attention. I wonder if all the projections of the economic consequences of climate change take into account the increase in allergies, since this is going to reduce worker productivity measurably for sure...

Kim KnowltonFeb 23 2011 12:35 PM

Nick, Your comment brings up a really important point: Most studies that project the costs of climate change deal largely with infrastructure damage, and ignore its effects on people's health. That's a huge oversight. As you point out, we need to account for reduced worker and student productivity, medical costs, years of healthy life lost -- those kind of human costs are critical to include, too. Thanks!

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