Effect of co-exposure to air pollution and house dust endotoxin on asthma and wheeze

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Project Period: 
Project Investigator(s): 
Angelico Mendy, Peter Thorne, UI Department of Epidemiology
Darryl Zeldin, Paivi Salo, NIEHS
Richard Cohen, Jesse Wilkerson, Social and Scientific Systems, Inc.
Charles Weir, HHS Office of Emergency Management

Air pollutants and house dust endotoxin are ubiquitous in our environment. Air pollutants exacerbate pre-existing asthma and evidence is mounting that it may cause the disease through oxidative stress and destruction of the airway mucosa. Endotoxin is also well known to cause bronchial asthma, although research suggests it might be protective against the atopic phenotype, especially with early-life exposure. Animal studies suggest that co-exposure to both air pollutants and endotoxin may have worse consequences on respiratory health than individual exposures. This study will investigate the effects of co-exposure to environmental pollutants on asthma and wheeze in humans in a representative U.S. sample. The research will lead to an increased understanding of environmental risk factors for asthma and wheeze to enhance prevention of these respiratory conditions.

Project Results: 

Homes in rural states with farming activities such as Iowa tend to have higher concentrations of endotoxin than the homes located in non-rural states. This work contributed to the better understanding of the association of endotoxin with respiratory diseases as well as the factors that might influence this relationship.

The study had three primary findings.

  1. House dust endotoxin and ambient air pollution are risk factors for asthma and animal studies suggest that they might have a synergistic effect on asthma
  2. In a large sample representative of the US population which included 6,488 participants, researchers examined the association of co-exposure to endotoxin and ambient air pollutants such as particulate matter - 2.5 um (PM2.5), nitrogen dioxide (NO2), and ozone (O3) with asthma outcomes
  3. Researchers found that co-exposure to elevated levels of house dust endotoxin and ambient PM2.5 was synergistically associated with emergency room visit for asthma in the past 12 months in all participants and while co-exposure to elevated concentrations of house dust endotoxin and ambient NO2 was associated with the outcome only in children.

Mendy A, Salo PM, Cohn, RD, Wilkerson J, Zeldin DC, Thorne PS. House Dust Endotoxin Association with Chronic Bronchitis and Emphysema. Environmental Health Perspectives (Online), 2018;126(3).

Mendy A, Wilkerson J, Salo PM, Cohn RD, Zeldin DC, Thorne PS. Exposure and Sensitization to Pets Modify Endotoxin Association with Asthma and Wheeze. The Journal of Allergy and Clinical Immunology: In Practice. 2018 Apr 21. Epub ahead of Print

Mendy A, Wilkerson J, Salo PM, Cohn RD, Zeldin DC, Thorne PS. Endotoxin predictors and associated respiratory outcomes differ with climate regions in the US. Environment international. 2018;112:218-26.