Research published in the esteemed journal BMJ Open reveals a strong connection between environmental exposure to polycyclic aromatic hydrocarbons (PAH) and increased risk of developing rheumatoid arthritis. PAH, toxic compounds produced from burning coal, oil, gas, wood, tobacco, or even during the grilling of meat, are omnipresent in our environment. Notably, the study sheds light on how PAH potentially mediates the majority of smoking’s effects on the risk of rheumatoid arthritis.
Conducted on a substantial sample size of 21,987 adults using data from the US National Health and Nutrition Examination Survey (NHANES), the study identifies a clear link between high levels of PAH and rheumatoid arthritis, even after accounting for potential influencers such as lifestyle, diet, and socioeconomic factors. Surprisingly, after factoring in PAH levels, smoking did not show a direct association with the disease risk.
This pioneering research emphasizes the critical influence of PAH, not only from smoking but also from diverse sources, underscoring the importance of understanding and managing our environmental exposures. Although this is an observational study, its findings can have far-reaching implications for health policies and personal lifestyle choices. Especially, individuals from lower socioeconomic backgrounds living in areas with poorer air quality might be particularly vulnerable, suggesting the need for targeted interventions.
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. Occupational and Environmental Medicine. https://bmjopen.bmj.com/content/13/5/e071514
Polycyclic Aromatic Hydrocarbons
Polycyclic aromatic hydrocarbons, often abbreviated as PAHs, are a group of over 100 different chemicals that are formed during the incomplete burning of coal, oil, gas, wood, garbage, or other organic substances such as tobacco and charbroiled meat. They are usually found as a mixture containing two or more of these compounds, such as soot.
PAHs are ubiquitous in our environment. They can be found in the air attached to dust particles and can be released from certain industrial processes, vehicle exhausts, cigarette smoke, and even during the cooking of certain foods. In addition to air, they can also be found in soil and water where they have been deposited. Many PAHs are lipophilic, meaning they tend to accumulate in the fat tissues of living organisms, and they can bioaccumulate in the food chain.
Some PAHs are manufactured. These pure PAHs usually exist as colorless, white, or pale yellow-green solids. PAHs are found in a wide range of commercially made products, like medicines, plastics, and dyes. They are also found in creosote, a commonly used wood preservative.
Exposure to PAHs can have detrimental health impacts. Several PAH compounds have been identified as carcinogenic, mutagenic, and teratogenic. Acute exposure can cause eye irritation, nausea, vomiting, diarrhea, and confusion. Long-term exposure can increase the risk of developing cancer, particularly lung, skin, and bladder cancer.
More recently, research has suggested a link between PAH exposure and the risk of developing rheumatoid arthritis. As your article title indicates, connecting the dots between environmental toxins like PAHs and disease risks is a burgeoning and important area of study.
Rheumatoid Arthritis: A Conventional Overview
Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by inflammation of the joints, which typically results in painful swelling, stiffness, and potentially progressive joint damage. It affects around 1% of the global population, and it is most common among women and older individuals. The disease manifests as the body’s immune system mistakenly attacking its own tissues, primarily affecting the lining of joints (the synovium), but it can also affect other organs of the body.
The exact cause of RA is not fully understood, but it is believed to involve a combination of genetic and environmental factors. Certain genetic variations can make an individual more susceptible to the disease, but the presence of these genes doesn’t guarantee its onset. Instead, environmental factors—such as exposure to cigarette smoke, air pollution, or infections—are thought to trigger the disease in people with these genetic predispositions. Certain lifestyle factors like poor nutrition, obesity, and a lack of physical activity are also known to increase the risk of RA.
Symptomatically, RA often presents as tender, warm, swollen joints, joint stiffness that is usually worse in the mornings and after inactivity, fatigue, fever, and weight loss. Over time, the inflammation associated with RA can cause joint deformity and erosion, and it can impact physical function. Diagnosing RA can be complex, involving a series of blood tests, imaging scans, and physical examinations. Although there is no known cure for RA, a variety of treatments can help manage the symptoms, prevent joint damage, and improve overall quality of life. These treatments typically involve a combination of medication, physical therapies, and in some cases, surgery.
BMJ Study: Unveiling the Connection Between PAH and RA
The research published in BMJ Open provides a comprehensive look at how exposure to polycyclic aromatic hydrocarbons (PAH) influences the risk of developing rheumatoid arthritis (RA). The study utilized data from the US National Health and Nutrition Examination Survey (NHANES) conducted between 2007 and 2016, encompassing 21,987 adults. Of the participants, 1,418 had been diagnosed with RA. Researchers used blood and urine samples to measure the concentration of PAH in participants, accounting for potential influencing factors such as dietary fibre intake, physical activity, smoking, household income, educational attainment, age, sex, and weight (BMI).
A standout finding from this study was that individuals in the top 25% of bodily PAH levels had the highest odds of having RA, regardless of their smoking status. After adjusting for the aforementioned influencing factors, the PAH known as 1-hydroxynaphthalene was found to be strongly associated with an 80% increased odds of RA. The association with other environmental toxicants, PHTHTEs and VOCs, which were also studied, disappeared after adjusting for potential confounders.
Interestingly, when researchers controlled for PAH levels in the body, smoking did not demonstrate a significant association with increased RA risk. This suggested that PAHs may mediate much of the relationship between smoking and RA. Further analysis demonstrated that the PAH level in the body accounted for 90% of the total effect of smoking on the risk of RA.
It is important to note, however, that the study was observational and therefore could not definitively establish a causal relationship between PAH exposure and RA. The researchers acknowledged the study’s limitations, such as the lack of measurements of environmental toxicants in fat (adipose) tissue and the absence of measurement of heavy metal levels, which have previously been linked to RA risk. Despite these limitations, this research provides a substantial contribution to our understanding of environmental influences on RA, especially regarding PAH exposure.
Similar Studies
Investigation into the connection between environmental exposure, particularly to polycyclic aromatic hydrocarbons (PAHs), and rheumatoid arthritis (RA) risk is a burgeoning field. As of my knowledge cutoff in September 2021, some related studies have shed light on this complex relationship.
A study published in the journal “Environmental Pollution” in 2016 examined the connection between traffic-related air pollution, a significant source of PAHs, and the risk of RA. The researchers found that individuals living in areas with high traffic pollution had a greater risk of developing RA, suggesting a potential role for environmental pollutants like PAHs.
Another study published in “The Lancet” in 2013 focused on early-life environmental exposure and risk of RA. This research indicated that children exposed to second-hand smoke, another source of PAHs, had an increased risk of developing RA as adults.
In a 2010 study published in “Arthritis Care & Research,” researchers found that occupational exposure to mineral oil, which can contain PAHs, was associated with an increased risk of developing RA in men.
Similarly, an earlier study in 2007 published in the “Annals of the Rheumatic Diseases” found that occupational exposure to certain chemical groups, including PAHs, was associated with an increased risk of developing anti-citrullinated protein antibody-positive RA.
These studies, while not as extensive as the recent BMJ Open study, suggest a potential link between environmental exposure to PAHs and the risk of developing RA. However, more research is required to further clarify and strengthen this link, taking into account other potential risk factors and the exact mechanisms of action.
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. Occupational and Environmental Medicine. https://bmjopen.bmj.com/content/13/5/e071514