How Climate Change Impacts Allergies and Asthma



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By P.K. Daniel 

Walk outside. What do you breathe?

You hope for clean air, free of harmful allergens and irritants, but climate change and air pollution are making that less likely. For the 1 in 7 Americans with respiratory conditions, the implications are troubling.

Many doctors and scientists think climate change is one factor behind a rise in allergies and the recent extreme pollen seasons in some areas of the country. Plants are blooming earlier and longer. And the extended growing season, fueled by rising temperatures and more frost-free days, is having an adverse effect on those with allergies and asthma.

“Climate warming itself will increase outdoor allergens,” says Norman H. Edelman, MD, senior consultant for scientific affairs with the American Lung Association. “Not only are allergy seasons getting longer, but also the climate’s getting hotter and that’s affecting ozone levels. And ozone is an airway irritant that causes inflammation in people who have asthma.”

Increased levels of airborne allergens and irritants means a higher risk for asthma flares and allergy exacerbations. A 2011 U.S. Department of Agriculture study reports that since 1995 the ragweed season has been extended by 2-4 weeks.

There is also the possibility that some airborne allergens may become more prevalent and potent as a result of increases in carbon dioxide.

Is Fracking Polluting the Air?

Another environmental concern is hydraulic fracturing, also known as fracking. It is the process of injecting liquid at high pressure into subterranean rocks to force open fissures and extract oil or gas. At the same time, it releases methane and other chemical compounds into the air that can be inhaled, potentially triggering asthma or making respiratory symptoms worse.

The Agency for Toxic Substances and Disease Registry (ATSDR), a federal public health agency of the U.S. Department of Health and Human Services, has received petitions to evaluate citizen concerns related to fracking operations.

Very little data has been collected to evaluate the health effects of fracking via emissions from compressor stations, holding ponds, silica use or increased truck traffic related to these operations. In the most extensive air monitoring, the Colorado Department of Health, ATSDR’s cooperative agreement partner, found some 64 air contaminants related to air exposures surrounding a compressor station. However, it was not possible to evaluate the actual health impact of the exposures.

Bottom line: More investigation is needed to evaluate fracking’s effect on air quality and health.

Jay M. Portnoy, MD, Director of Allergy, Asthma & Immunology at Children’s Mercy Hospitals & Clinics in Kansas City, Missouri, addressed climate change and its effects at the annual scientific meeting of the American College of Allergy, Asthma & Immunology (ACAAI) in November 2014, in Atlanta.

“The prevalence of allergies and asthma has been increasing at least since the 1960s,” he says. “This change is directly related to increases in atmospheric carbon dioxide. Higher levels of CO2 cause plants to make more pollen, and the pollen is more potent.”

And then there’s the so-called “priming effect” caused by up-and-down temperatures common in early spring. During an initial rise in spring temperature, grass and trees release a first round of pollen; the resulting allergic reaction primes the immune system for more severe reactions later in the season, says Stanley Fineman, MD, an allergist and immunologist with Atlanta Allergy & Asthma and ACAAI past president.

Dr. Fineman stressed that it’s important for people to see a board-certified allergist for testing to find out what they are allergic to. “Once these allergens are identified, the patient can follow published reports of pollen counts and take precautions,” he says.

During these longer allergy seasons with higher pollen counts, patients may find they need to use higher doses or more potent medication to control symptoms.

“Alternatively, they may require daily medication instead of ‘as needed,’ and the length of time that daily medication is needed will likely be extended,” says Sakina Bajowala, MD, an allergist-immunologist at Kaneland Allergy & Asthma Center in North Aurora, Illinois.

The most reliable source for pollen and mold counts is from the National Allergy Bureau (NAB) at the American Academy of Allergy, Asthma & Immunology (AAAAI) website www.AAAAI.org.

“The NAB counts are based on actual sampling by board-certified allergists, rather than predictive modeling,” Dr. Bajowala says. “It is wise for people with allergies and asthma to routinely check pollen counts and air quality. Doing so can help them plan their day. For example, you may wish to limit outdoor activities on days when pollen counts are especially high.”

The Air Out There

Climate change affects air pollution as well, including increased levels of ozone, fine particles and dust, and increases in mold spores are impacting the millions of people with allergies and/or asthma.

Several studies report links between air pollution exposure and the development of asthma. Researchers have found a connection between increased hospital admissions for asthma and dust, dirt, soot and smoke caused by forest fires, wind erosion and human activities such as car and truck emissions, smokestacks and construction.

Major transportation corridors create pockets where pollution levels are higher than surrounding areas, and these areas usually house populations with high rates of asthma and lower incomes. Ozone, the primary ingredient in smog that often blankets urban areas in the summer, is also blown into these communities where mostly minority populations reside.

“Many inner city populations live near highways, and increased auto and truck diesel exhaust have been correlated with increased asthma diagnosis and morbidity,” Dr. Fineman says.

Local air pollution control agencies, as well as the Environmental Protection Agency’s website www.airnow.gov, publish daily air quality updates. Additionally, the American Lung Association has a free app for iPhone and Android devices called State of the Air. It provides daily and next-day air quality information based on zip codes and can provide alerts when air pollution is at unhealthy levels.

Reducing carbon pollution will reduce the number of ozone alerts and particle pollution. “The more we can delay or reduce the amount of climate change caused by carbon pollution, the better off we’re going to be for protecting our health,” says American Lung Association’s Janice E. Nolen, assistant vice president for national policy.

Sea Change

Another climate change issue: flooding and rising sea levels. Both can have a worsening effect on asthma because of the potential increase of mold in both indoor and outdoor air.

Thunderstorm Asthma

While rain is beneficial in improving drought conditions and it can “clean” the air of allergens, thunderstorms have been known to trigger asthma attacks. Indeed, a rise in asthma-related emergency room visits during and after thunderstorms has been reported.

This somewhat rare phenomenon, called “thunderstorm asthma,” may be caused by a plume of mold called Alternaria that is sent into the air just prior to the storms.

“The low barometric pressure associated with storm systems can precipitate the release of mold spores, leading to increased allergy and asthma symptoms in susceptible individuals,” says Sakina Bajowala, MD.

Some studies suggest climate change could result in stronger thunderstorms, with winds spreading more pollen and mold spores. Lightning can also affect asthma since it increases ozone in the air.

Childhood asthma morbidity and mortality numbers in New Orleans, which is below sea level, has been among the highest in the nation – and that was before Hurricane Katrina struck in 2005. Major flooding caused by Hurricane Katrina led to a significant increase in mold, although levels have improved in recent years.

Mold growth can lead to the release of allergens or microbial volatile organic compounds (VOCs), mold’s musty odor that can act as an airway irritant. Living in damp indoor environments – where mold and dust mites thrive – is a risk factor for asthma flares.

Meanwhile, wildfires brought on by drought and dry, hot climates bring their own set of health hazards. Fire causes smoke, which is filled with toxins, VOCs and fine particles.

These substances, which can hang in the air for days, irritate the airways, making asthma worse and increasing the risk of respiratory infections such as bacterial pneumonia and bronchitis. “These particles can blow hundreds of miles,” Nolan says. “And it doesn’t take a lot of exposure or really high levels to do serious harm.”

For people with asthma and allergies, following a management plan that reduces airway inflammation and preventing symptoms year-round are proactive steps against the consequences of climate change. Along with that, check pollen counts and air quality information online or on TV newscasts, and adapt your daily routine to avoid or minimize exposure to allergens and irritants.

Talk with an allergist if you think climate or air pollution is impacting your symptoms and ask whether you need to adjust your management plan or medication schedule. Find out whether immunotherapy treatments for pollen, mold or other allergens are right for you.


Reviewed by Stanley Fineman, MD, Tera Crisalida, PA-C and Eileen Censullo, RRT