Air Pollution Linked to Lung Infections, Especially in Young Children

Exposure to a short-term increase in pollution-causing airborne particles called fine particulate matter 2.5 (PM) is linked to the development of acute lower respiratory infection (ALRI) in young children, as well as additional doctor visits, according to recent respiratory research.

The landmark study is the largest respiratory study to date on this issue, involving more than 100,000 patients. It was published recently in the American Journal of Respiratory and Critical Care Medicine, the journal of the American Thoracic Society. The research was conducted by a team from Intermountain Healthcare, Brigham Young University, and the University of Utah.

"The most important finding of this study is that infectious processes of respiratory disease may be influenced by particulate matter pollution at various levels," said lead author Benjamin Horne, PhD, director of cardiovascular and genetic epidemiology at the Intermountain Medical Center Heart Institute in Salt Lake City, Utah, in a statement. "The exact biological implications of the study's findings require further investigation."

Horne and colleagues studied 146,397 patients, mostly children under 2 years old, who were treated for ALRI between 1999 and 2016 at Intermountain Healthcare facilities throughout Utah's Wasatch Front region. The Wasatch Front is approximately 80 miles long and 10-20 miles wide, bordered on both sides by mountains. It consists primarily of suburbs, but also includes the cities of Salt Lake City, Ogden, and Provo/Orem. About 80% of Utah’s population lives in the region.

ALRI are a major source of morbidity and mortality often caused by viruses such as respiratory syncytial virus and influenza virus. ALRI occur more often in winter and may be associated with greater exposure to elevated ambient air pollution, including PM2.5 and other air pollutants.

Until now, evidence linking short-term elevation in PM2.5 with ALRI was weak and contradictory. The primary aim of this study was to determine if there was an association between these fine particulates and ALRI in very young children, with a secondary objective of finding the same associations for older children, adolescents and adults.

In this study, each short-term 10 μg/m³ increase in PM2.5 was associated with 15%-23% higher odds of contracting an ALRI. In other words, a short-term exposure to elevated PM2.5 air pollution may be associated with greater healthcare utilization for the diagnosis of ALRI among both children and adults.

The higher number of healthcare encounters for ALRI followed the elevated PM2.5 exposure between 1 to 4 weeks. The timeframe differed depending on respiratory pathogen and age of subjects.

PM2.5 levels were estimated based on data from air quality monitoring stations along the Wasatch Front. Measurements were also made at secondary locations. Short-term periods of PM2.5 elevation were matched with the timing of increases in healthcare visits for ALRI.

The research team found ALRI associated with elevated levels of PM2.5 in both children and adults—even in newborns and toddlers up to age 2, who represented 77% (112,467) of those who had an ALRI diagnosis.

Bronchiolitis, a condition in which small breathing tubes in the lungs called bronchioles become infected and clogged with mucus, is the most common acute lower respiratory infection in children.

Fifty percent to 90% of bronchiolitis cases are caused by RSV, which is the most common cause of hospitalization in the first 2 years of life. Sixty-four percent of individuals studied had a diagnosis of bronchiolitis.

"Overall, it took about 2-3 weeks for the ALRI hospitalizations or clinic visits to occur in this study after the rapid rise in PM2.5 had been observed," said Horne.

Seventeen children aged 0-2, 9 children aged 3-17, and 81 adults over the age of 18 died within 30 days of diagnosis with ALRI in an analysis of death rates among the study population.

Horne said it is possible that air pollution makes the 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.”

It could also be that increases in PM2.5 force people indoors, he said, where they spend more time with people who are sick with infectious disease.

According to the statement, motor vehicles contribute about 48% of emissions that lead to the formation of fine particulates. Small industry and businesses such as gas stations and dry cleaners, as well as home heating, emit about 39% of all fine particulates. Large manufacturing accounts for 13%.

Earlier this week, 17 states announced they were suing the Trump administration for a plan announced by the Environmental Protection Agency to reverse Obama-era tailpipe emission rules that were to go into effect in 2022 for vehicle models through 2025, saying the move was a violation of the Clean Air Act.

Nearly 60% of US children live in counties with PM2.5 concentrations above air quality standards.

Reference

Horne BD, Joy EA, Hofmann MG, et al. Short-term elevation of fine particulate matter air pollution and acute lower respiratory infection [published online April 13, 2018]. Am J Respir Crit Care Med. doi.org/10.1164/rccm.201709-1883OC.