Introduction

Most health care providers involved with direct patient care will report that the number of patients with allergies and asthma is increasing. Patients who have had these conditions for years report that their symptoms are getting worse. There seems to be a direct correlation with air that patients breath and the development of allergies and asthma and the worsening of symptoms. It is important for physicians to understand the connection to chemicals in our air and allergies and asthma to help provide the best comprehensive and integrative treatment approach.

Allergies and Asthma

According to the American Academy of Allergy, Asthma and Immunology, https://www.aaaai.org, allergies and asthma can be due to a reaction to a drug, pet, food, pollen, trees, and grasses. The immune system responds to allergen by releasing histamine and chemical mediators that cause symptoms, an IgE mediated event.

Seasonal allergic rhinitis is most often caused by pollen as well as triggered by smoke and air pollution. Classic rhinitis symptoms include nasal congestion, rhinorrhea, sneezing and itching. Nonallergic rhinitis causes year-round symptoms, and this condition differs from allergic rhinitis because the immune system is not involved—not an IgE mediated event but can also be linked to air pollution, dust.¹

Asthma presents as wheezing, shortness of breath, chest tightness or pain, and coughing. Asthma involves airway inflammation, intermittent airflow obstruction, and bronchial changes. Asthma can be triggered by allergies such as pet dander, dust mites, pollen, or mold. Non-allergic triggers include cold air or changes in the weather, dust, smoke, and air pollution. Asthma, like allergies, is an immune mediated condition. A trigger or antigen exposure leads to lymphocyte and cytokine response creating airway inflammation and asthma symptoms.¹

Environmental toxicants can alter immune response and function in the body and are linked to immune-mediated diseases such as asthma and allergies. The pro-inflammatory immune response induced by exposure to some toxicants contributes to cellular changes involved in allergies and asthma. The immune system is composed of multiple organs and cells and an appropriate immune response involves the interaction of multiple cell types, immunoglobulin, and cytokines. These responses are altered by exposure to certain chemicals and/or toxicants creating immunotoxicity.²

Air Pollution

Outdoor air pollution is caused by solid and liquid particles and certain gases that are suspended in the air. These come from car and truck exhaust, factories, dust, pollen, mold spores, volcanoes, and wildfires. They are from fossil fuels—coal, petroleum and wood, car exhaust, factories, and wildfires—and form through chemical reactions in the air.³ Outdoor air pollution consists of particulate matter (PM), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2). arsenic, cadmium, lead and mercury, pesticides, and volatile organic compounds (VOCs).³ Climate change is expected to create more outdoor air pollution. Warmer temperatures, change in precipitation patterns, higher ocean acidity, and reduced sea-ice cover will have effects on concentrations of toxicants in the environment. Higher temperatures mean more ozone air pollution, increase in pests and subsequent increase in pesticide use in agriculture.^{4 ,5}

Indoor air is just as bad if not worse than outdoor air in some homes. Common chemicals and toxicants found include carbon monoxide (CO), formaldehyde from pressed wood products, lead, nitrogen dioxide (NO2) pesticides, radon, indoor particulate matter, tobacco smoke– toxic metals, solvents, and volatile organic compounds (solvents, PAHs). These come from the following:

• Fuel-burning combustion appliances
• Smoking indoors
• Fireplaces
• Building materials and furnishings as diverse as:
• Deteriorated asbestos-containing insulation
• Newly installed flooring, upholstery or carpet
• Cabinetry or furniture made of certain pressed wood products
• Products for household cleaning and maintenance, personal care, or hobbies
• Central heating and cooling systems and humidification devices. ⁶

Outdoor sources such as radon, pesticides, and outdoor air pollution also pollute indoor air.

The Connection

To help emphasize the link between toxicants present in air pollution and asthma and allergies, a few examples are outlined here.

Polyaromatic hydrocarbons (PAHs) are created when organic materials are burning in high temperatures. PAHs can react with ultraviolet light and other pollutants (e.g., ozone, nitrogen oxides and nitrate radicals). They enter the lungs causing inflammation and affecting respiratory health. There is an association between exposure to PAHs, concentrations of air pollutants, and allergic and non-allergic asthma, including increased symptoms of asthma, risk of asthma exacerbations, and decreased lung function.⁷

The use of insecticides and pesticides around the home is linked to allergies and asthma. A large Canadian cohort study found an association between exposure to organophosphates and reduced lung function in the adult general population and pyrethroids and reduced lung function in children and adolescents.⁷

Mercury from coal burning powerplants can travel long distances in the air and end up in both children and adults. Blood concentrations of mercury from air pollution in children are associated with allergies, asthma and elevated IgE.⁷

Cadmium is present in cigarette smoke and is also released from natural sources such as volcanos and forest fires. Studies show that urinary elevations of cadmium is linked with asthma. The blood level of cadmium had an association with self-reported asthma and allergies.⁷ Chronic exposures to arsenic and lead is also associated with asthma and allergies.⁷

Volatile organic compounds (e.g., solvents, formaldehyde) are present in outdoor ad indoor air. Exposure is linked to allergies, asthma, airway inflammation, respiratory symptoms, oxidative stress, and decreased lung function.⁸

Avoidance

A discussion of avoiding toxicants present in air pollution is challenging since it is difficult to control outdoor air. Many chemicals in outdoor air are determined by the size of the city where someone lives, number of cars in the road, air traffic, nearby industry, and agriculture, and is dependent on temperature, precipitation, and many other factors. So, we do the best we can with avoidance and improving our air quality. According to the Environmental Protection Agency and the American Lung Association, there are ways to help improve air quality both outdoors and indoors.

Some ways to help improve outdoor air include the following:

• Commit to one day a week to carpool or public transportation
• Refill your gas after dark.
• Instead of idling at a drive-through, park your car, and go inside.
• Join your company’s travel reduction program, ride-share system, or light rail pass.
• On No Burn Days, choose not to burn a fire in your fireplace or backyard.
• Don’t use pesticides around the yard
• Stop smoking anything and vaping
• Don’t grill meat and fish at high temperatures

Some ways to help improve indoor air include

• HEPA air filtration in the bedroom
• Stop smoking anything or vaping
• Change cleaning and personal care products to eliminate VOCs
• Don’t use non-stick pans to eliminate PFOS
• No solvent based or fragranced products in the home
• Use non-toxic mattresses, furniture, carpeting and paint
• Test your home for radon

Summary

The evidence is clear that toxicants from air pollution play a role in allergies and asthma symptoms. Physicians should always be aware of the air quality where they practice and screen patients for chemical exposure. This type of approach to health addresses the root cause of allergies and asthma. Educating patients on avoidance and ways to improve air quality is key to prevention and management of asthma and allergies.

References

1. AAAAI | American Academy of Allergy, Asthma & Immunology. Accessed 8/15/2022
2. Duramad P, Holland NT. Biomarkers of immunotoxicity for environmental and public health research. Int J Environ Res Public Health. 2011 May;8(5):1388-401.
3. World Health organization. Ambient Outdoor air pollution. Sept 2021. https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health. Accessed 8/13/2022
4. Balbus JM, et al. Implications of global climate change for the assessment and management of human health risks of chemicals in the natural environment. Environ. Toxicol. Chem. 2013;32:62–78.
5. Moe SJ, et al. Combined and interactive effects of global climate change and toxicants on populations and communities. Environ Toxicol Chem. 2013 Jan;32(1):49-61.
6. Environmental protection agency. Introduction to air quality. Dec 16, 2021. https://www.epa.gov/indoor-air-quality-iaq/introduction-indoor-air-quality. Accessed 8/12/2022
7. Mattila T, et al. Scoping Review-The Association between Asthma and Environmental Chemicals. Int J Environ Res Public Health. 2021 Feb 1;18(3):1323.
8. Kwon JW, Park HW, Kim WJ, Kim MG, Lee SJ. Exposure to volatile organic compounds and airway inflammation. Environ Health. 2018 Aug 7;17(1):65