MedicalResearch.com Interview with:
Benjamin D. Horne, PhD
Director of Cardiovascular and Genetic Epidemiology
Intermountain Heart Institute
Intermountain Medical Center
Salt Lake City, Utah
MedicalResearch.com: What is the background for this study?
Response: Evidence suggests that short-term elevations (even for just a few days) of fine particulate matter air pollution (PM2.5, which is particulate matter less than 2.5 um or about one-thirtieth the diameter of a human hair) is associated with various poor health outcomes among adults, including myocardial infarction, heart failure exacerbation, and worsening of chronic obstructive pulmonary disease symptoms. Studies of long-term exposure to moderately elevated levels of PM2.5 indicate that chronic daily air pollution exposure may contribute to death due to pneumonia and influenza.
Research regarding the association of short-term elevations in PM2.5 has provided some limited evidence of a possible association between short-term PM2.5 increases and infection with respiratory syncytial virus (RSV) or bronchiolitis in children, but scientifically these reports have been weak and unreliable, probably because they have only looked at a period of a few days to a week after short-term PM2.5 elevations. An evaluation of a very large population in a geographic location that provides a wide variation in PM2.5 levels from lowest to highest levels and that examines longer periods of time after the PM2.5 elevations is needed to determine whether a PM2.5 association with lower respiratory infection exists.
MedicalResearch.com: What are the main findings?
Response: Among young children aged 0-2 years of age, short-term increases in PM2.5 were associated with a 15% higher risk of acute lower respiratory infection (ALRI) for every additional +10 ug/m3 (micrograms per cubic meter) of PM2.5 air pollution level. Acute lower respiratory infection was measured by observing hospital and clinic visits where the final diagnosis was bronchiolitis or an infection that leads to it. The primary pathogen among this age group was RSV. The ALRI hospitalizations or clinic visits occurred primarily about 2-3 weeks after the rise in PM2.5 had been observed. Subanalyses demonstrated that the risk was stronger for hospitalization, although outpatient clinic visits followed a similar but weaker pattern of risk, and essentially no difference in risk was observed between females and males.
Among children aged 3-17 years of age and in adults, a greater risk of acute lower respiratory infection was also observed after short-term elevations in PM2.5 air pollution. For children 3-17 years, a 32% higher risk of ALRI was observed for each +10 ug/m3 of PM2.5, while among adults the risk was 19% higher for every +10 ug/m3 in additional PM2.5 elevation. The influenza virus was the primary pathogen in older children and adults, and the risk peaked after just one week although the risk association remained present and statistically significant for several weeks afterwards. The risk association was most strongly observed for hospitalization for 4 weeks after the PM2.5 elevation, while the effect existed only for the first week after PM2.5 elevation for those only seeking healthcare in an outpatient environment.
MedicalResearch.com: What should readers take away from your report?
Response: This study of short-term elevation of PM2.5 air pollution and acute lower respiratory infection suggests that infectious processes of respiratory disease may be influenced by particulate matter pollution at various levels. The exact biological implications of the study’s findings require further investigation, but this includes the possibility that the air pollution itself may make the human body more susceptible to infection or may impair the body’s ability to fight off the infectious agents. It may be that PM2.5 causes damage to the airway so that a virus can successfully cause an infection or that PM2.5 impairs the immune response so that the body mounts a less effective response in fighting off the infection. This could lead to longer periods of acute lower respiratory infection symptoms or more severe symptoms requiring a higher intensity of medical care for the infected individual. It may also be that periods of acute increases in PM2.5 lead people to stay indoors more where they are in closer contact with others who carry infectious agents and can transmit the infection to them.
Even more, the practical implications for prevention of ALRI and amelioration of symptoms include that when an acute increase in the level of PM2.5 occurs, people should be more vigilant in their efforts to prevent respiratory infections. This may include common infection control methods such as washing hands at appropriate times, avoiding contact with infected individuals and large crowds or concentrated groups of people, and avoiding touching the face including eyes, nose, and mouth.
Other methods can be found here: https://www.cdc.gov/flu/protect/stopgerms.htm. Furthermore, the study suggests that it is possible to reduce risk of ALRI by reducing exposure to the PM2.5 air pollution during times of elevated levels. Methods for reducing PM2.5 exposure include staying indoors in cleaner air buildings, conducting outdoor activities in the early morning hours when air pollution levels are lower, and avoiding roadways and highways where mobile sources of air pollution congregate. Informational sheets about avoiding air pollution exposure can be found here: https://intermountainhealthcare.org/health-information/health-library/patient-handouts/search-results/?Search=air%20pollution, such as the following document regarding air quality in early childhood:https://intermountainhealthcare.org/ext/Dcmnt?ncid=527914751.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: Future research should attempt to replicate this study’s findings in geographically distinct populations. Biological work should also be conducted to examine the causal pathways that may be involved to determine whether air pollution is a cause of susceptibility to acute lower respiratory infection, if it adds to the severity of infection or prolongs recovery, or if other coincidental factors are involved and air pollution is not an actual cause of ALRI risk.
MedicalResearch.com: Is there anything else you would like to add?
Response: One of the approaches that we are pursuing at Intermountain is to utilize short-term elevations in PM2.5 air pollution as a nudge or trigger to change staffing, supply chain, and other healthcare processes and practices to prepare for larger patient influxes at hospitals and clinics. Further, it may be used to improve educational information and delivery of that information for at risk individuals, as well as to initiate contact with recent obstetric patients to remind them about the potential risks and how to ameliorate those risks.
Any disclosures? I have no financial or other possible conflicts of interest to report.
Am J Respir Crit Care Med. 2018 Apr 13. doi: 10.1164/rccm.201709-1883OC. [Epub ahead of print]
Short-term Elevation of Fine Particulate Matter Air Pollution and Acute Lower Respiratory Infection
Horne BD1, Joy EA2,3, Hofmann MG4,5, Gesteland PH6,4, Cannon JB7, Lefler JS7, Blagev DP8,9, Korgenski EK4, Torosyan N10, Hansen GI11, Kartchner D10,12, Pope Iii CA13.
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