Several Pollutants Linked to Increased IBS Incidence Rate

Philip N. Okafor, MD, MPH

Various pollutants increase the incidence rate of irritable bowel syndrome (IBS) in communities.

A team, led by Philip N. Okafor, MD, MPH, Department of Gastroenterology and Hepatology, Stanford University School of Medicine, quantified the relationships between 7 pollutants and the zip code-level incidence of IBS, functional dyspepsia, inflammatory bowel disease (IBD), and eosinophilic esophagitis (EoE) in California.

In previous studie, investigators have found a connection between environmental pollutants and gastrointestinal diseases.

Pollutants and Gastrointestinal Disease

In the study, the investigators linked claims in Optum’s Clinformatics Data Mart (CDM) with environmental exposures in California, identified from CalEnviroScreen 3.0.

The investigators identified adult patients with new diagnoses of each gastrointestinal disease and estimated claims-derived, zip-code level disease incidence rates between 2009-2014 and 2016-2019.

They then took this data and used multivariable negative binomial regression models to test associations between ozone, particulate matter <2.5 microns [PM2.5], diesel emissions, drinking water contaminants, pesticides, toxic releases from industrial facilities, and traffic density and zip-code level incidence of the gastrointestinal disease and a negative control outcome, adjusting for numerous potential confounders.

The results show zip code-level IBS incidence was associated with PM2.5 (P <0.001 in both eras) and airborne toxic releases from facilities (P <0.001 in both eras).

They also calculated that an increase of 1 microgram/m3 in PM2.5 or 1% in toxic releases equates to an increase in the IBS incidence rate of about 0.02 cases per 100 person-years.

For traffic density and drinking water contaminant exposures, these pollutants were linked to increasing IBS incidence. However, in both eras these associations were not significant.

Exposure to PM2.5, drinking water contaminants, and airborne toxins releases from facilities were also linked to functional dyspepsia incidence, but not in both eras.

There were no significant associations found between pollutants and IBD or EoE incidence.

“Exposure to PM2.5 and airborne toxic releases from facilities are associated with higher IBS incidence among a cohort of commercially-insured Californians,” the authors wrote. “Environmental pollutant exposure was not associated with the incidence of IBD and EoE in this cohort.”

Air Pollution

Nearly half of all Americans are now living in regions with unhealthy grades of air pollution, according to the 2022 American Lung Association (ALA) State of the Air Report.

Findings from the 23rd iteration of the annual national report on particulate matter and ozone-related climate health showed that more than 137 million Americans are living in areas with unhealthy levels of particle pollution or ozone—a 2.1 million increase from the 2021 report.

An additional 9 million more Americans were affected by daily spikes in potentially deadly particle pollution than observed last year, and the rate of “very unhealthy” and “hazardous” air quality days in the past 3 years reached an all-time high for the two-decade report.

More than 63 million Americans lived in counties that received an “F,” or failing, grade for spikes in daily particle pollution. By far, the most impacted region in the US during this time period was the West; all but 1 of the 25 worst cities for short-term particle pollution was in the western half of the country.

The Fresno-Madera-Hanford region of California was the lone area to surpass 50 weighted average days of poor particulate matter. Another 11 California cities were in the top 25, as were 9 Pacific Northwest cities.

The study, “Environmental Pollutants are Associated with Irritable Bowel Syndrome in a Commercially Insured Cohort of California Residents,” was published online in Clinical Gastroenterology and Hepatology.