BALTIMORE — A recent study suggests that barbecuing could potentially increase the risk of developing rheumatoid arthritis due to the release of polycyclic aromatic hydrocarbons (PAHs). These particles, which are environmental pollutants, form during the combustion of substances like coal, oil, gas, and wood, as well as during the flame grilling of meat and other foods.
Apart from being produced when food is grilled, PAHs can also originate from smoking tobacco. Upon inhalation, these chemicals enter the body. The study posits that exposure to PAHs may heighten the risk of rheumatoid arthritis, a chronic autoimmune disease where the immune system mistakenly attacks the cells lining the joints. Over time, this leads to damage to these cells, the cartilage, and nearby bone.
Rheumatoid arthritis primarily affects the hands, wrists, and feet, causing joint pain, swelling, and stiffness. The exact cause of this condition remains unclear, but researchers believe it is a complex interplay of genetic factors, sex, age, and environmental factors, including smoking, nutrition, and lifestyle.
Researchers seeking to identify potential risk factors for rheumatoid arthritis analyzed responses to the U.S. National Health and Nutrition Examination Survey (NHANES) collected between 2007 and 2016. They studied a variety of toxicants, including PAHs, PHTHTEs (chemicals used in manufacturing plastics and consumer products), and volatile organic compounds (VOCs) derived from paints, cleaning agents, and pesticides.
This study encompassed nearly 22,000 adults, 1,418 of whom had rheumatoid arthritis, while the remaining 20,569 did not. The team gathered blood and urine samples to measure the total amount of PAH, PHTHTEs, and VOCs in the body. They discovered that 7,090 participants had PAH in their system, 7,024 had PHTHTEs, and 7,129 had VOCs.
Interestingly, the highest odds of developing rheumatoid arthritis were found among those with the top 25 percent of bodily PAH levels, regardless of their smoking status. In particular, people with the PAH 1-hydroxynaphthalene in their body were 80 percent more likely to have rheumatoid arthritis. However, people with high levels of PHTHTEs and VOCs did not show an increased risk of rheumatoid arthritis.
The researchers discovered that the PAHs from smoking were the only tobacco-related factor significantly contributing to the increased risk of rheumatoid arthritis. Indeed, the presence of PAHs accounted for 90 percent of the total effect that smoking had on the risk of this disease.
The study also considered various potentially influential factors, such as dietary fiber intake, physical activity, smoking, household income, educational attainment, age, sex, and body mass index (BMI). According to the research team, led by Dr. Christopher D’Adamo from the University of Maryland School of Medicine, PAH levels are typically higher in adults who smoke. However, PAH exposure can also come from other sources, including indoor environments, motor vehicle exhaust, natural gas, wood or coal burning fires, asphalt road fumes, and grilled or charred foods.
The research emphasizes that poorer households, which often experience worse indoor air quality and may be located near major roadways or high-traffic areas, could be particularly exposed to these sources of PAHs.
As the study is observational, the researchers cannot definitively establish a causal link between pollutants and arthritis. Additionally, the research faced limitations, such as the unavailability of measurements for environmental toxicants in fat tissue. The study also did not measure heavy metal levels in the body, which have been previously associated with rheumatoid arthritis risk. For instance, cigarettes are a significant source of the heavy metal cadmium.
Despite these limitations, the authors assert that, to their knowledge, this is the first study that suggests PAHs not only contribute significantly to the relationship between smoking and rheumatoid arthritis but also independently increase the risk of this disease.
The researchers emphasize the significance of their findings, given that PAHs are prevalent in the environment, originate from various sources, and are mechanistically linked by the aryl hydrocarbon receptor to the underlying pathophysiology of rheumatoid arthritis.
In conclusion, while more research is needed to fully understand the relationship between PAHs and rheumatoid arthritis, the study suggests a potential link that warrants further investigation. Public health initiatives to reduce PAH exposure, particularly in vulnerable populations, may also be a meaningful step towards lowering the risk of developing this debilitating condition.
The study is published in the journal BMJ Open.
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South West News Service writer Alice Clifford contributed to this report.