Study on PAHs and Rheumatoid Arthritis

A new study by Chris D'Adamo and his team found that toxic chemicals from car exhaust, smoking, and backyard grills can increase the risk of developing rheumatoid arthritis (RA), an autoimmune disease. The findings of this study were published in BMJ Open.

These chemicals are called polycyclic aromatic hydrocarbons (PAHs). They are produced when coal, oil, gas, wood, and tobacco are burned. Grilling meat and other foods over an open fire also contributes to the production of PAHs.

Rheumatoid arthritis is an autoimmune and inflammatory disease that primarily affects joints, causing tissue damage and long-term pain. Joints can become deformed, and patients may feel unsteady underfoot. Women are more likely than men to develop rheumatoid arthritis. The cause is unknown, but environmental factors such as genes, gender, age, smoking, diet, and lifestyle are thought to be involved.

Study Details

For the study, the researchers used data from the US National Health and Nutrition Examination Survey, which surveyed about 22,000 adults between 2007 and 2016. Over 1,400 had rheumatoid arthritis. Blood and urine samples were tested to determine levels of PAHs and other chemicals in the body. The 25% of people with the highest PAH levels were most likely to develop rheumatoid arthritis, regardless of whether they were former or current smokers.

Taking into account dietary fiber, physical activity, smoking, income, education, age, sex, and weight, having PAHs (i.e., 1-hydroxynaphthalene) was strongly associated with a higher risk of developing rheumatoid arthritis (80%).

Blood and urine samples taken from about 22,000 adults found that those with the highest PAH levels were at the highest risk of developing rheumatoid arthritis. Increased RA prevalence was observed in participants with the highest quartile of PAH for a variety of individuals, whereas in the fully fitted model, it remained associated only with 1-hydroxynaphthalene. In a perfectly fitted model, PAH body load was found to be associated with RA. Interestingly, smoking was not associated with RA after considering the physical burden of PAH. A mediation analysis showed that PAH body burden accounted for 90% of the overall effect of smoking on RA. PHTHTE and VOC metabolites were not associated with RA in the perfect fit model.

Reference

Beidelschies, M., Lopez, R., Pizzorno, J., Le, P., Rothberg, M. B., Husni, M. E., & D’Adamo, C. (2023). Polycyclic aromatic hydrocarbons and risk of rheumatoid arthritis: a cross-sectional analysis of the National Health and Nutrition Examination Survey, 2007–2016. In BMJ Open (Vol. 13, Issue 5, p. e071514). BMJ. https://doi.org/10.1136/bmjopen-2022-071514