Environmental triggers for inflammatory bowel disease

Inflammatory Bowel Disease (IBD) is an inflammatory condition that affects the bowel, and its cause is complex and not well understood. It is thought that factors such as genetics, environmental influences, and the gut microbiome affect the risk of developing IBD. Some environmental factors that can contribute to the development of IBD include the presence of heavy metals, pesticides, organic pollutants, and air pollution. Heavy metals such as copper, lead, and cadmium can alter the gut microbiome and lead to a ‘leaky gut’ (the damaged lining of the small intestine allows bacteria and foreign substances to enter the bloodstream). Patients with IBD generally have higher concentrations of these metals than people in the general population. Pesticides and organic pollutants can also affect the gut microbiome and contribute to a ‘leaky gut.’

Long-term exposure to air pollution has been linked to the development of not only respiratory conditions but also other inflammatory disorders such as rheumatoid arthritis and multiple sclerosis, which have similar disease development processes to IBD. These factors are thought to have contributed to a 47.5% increase in global IBD cases, from 3.3 million in 1990 to 4.9 million in 2019.

A 2024 literature review of current research regarding the development of IBD and air pollution found correlations with multiple types of gases produced by air pollution. The gases in air pollution include carbon dioxide, nitric oxides, and particulate matter (PM) of varying sizes, which can be produced by cars, factories, and forest fires. For reference, air pollution levels in Australia are generally low, with cities such as Melbourne having an average PM 2.5 of 6.5 μg/m³, below the Australian government target of 8 μg/m³. However, this can increase dramatically, such as during the 2019-2020 bushfires, peaking at 470 μg/m³ on January 14, 2020.

PM particles, once breathed into the lungs, are cleared into the intestine, where they can produce inflammatory molecules and interact with the gut microbiome. Specifically, exposure to PM 2.5 has been associated with IBD, and with increases in PM 2.5 exposure, the chance of needing intestinal surgery increases. Countries with higher air pollution overall have a higher rate of hospitalizations for IBD patients, with every increase of ten units associated with a 40% increase in hospitalizations. Nitric dioxide pollution was also associated with an increase in overall mortality in IBD patients.

More research is needed to investigate the exact disease processes that each air pollutant contributes to the development of IBD, as well as the duration, amount, and length of exposure to air pollution needed to cause them.

Any information provided in this article is not intended as medical advice. If you have any concerns or questions, we recommend discussing them with your doctor.