A follow-up study of occupational styrene exposure and risk of autoimmune rheumatic diseases

Contributions of Synthetic Chemicals to Autoimmune Disease Development and Occurrence

PURPOSE OF REVIEW

Exposure to many synthetic chemicals has been linked to a variety of adverse human health effects, including autoimmune diseases. In this scoping review, we summarize recent evidence detailing the effects of synthetic environmental chemicals on autoimmune diseases and highlight current research gaps and recommendations for future studies.

RECENT FINDINGS

We identified 68 recent publications related to environmental chemical exposures and autoimmune diseases. Most studies evaluated exposure to persistent environmental chemicals and autoimmune conditions including rheumatoid arthritis (RA), systemic lupus (SLE), systemic sclerosis (SSc), and ulcerative colitis (UC) and Crohn's disease. Results of recent original research studies were mixed, and available data for some exposure-outcome associations were particularly limited. PFAS and autoimmune inflammatory bowel diseases (UC and CD) and pesticides and RA appeared to be the most frequently studied exposure-outcome associations among recent publications, despite a historical research focus on solvents. Recent studies have provided additional evidence for the associations of exposure to synthetic chemicals with certain autoimmune conditions. However, impacts on other autoimmune outcomes, particularly less prevalent conditions, remain unclear. Owing to the ubiquitous nature of many of these exposures and their potential impacts on autoimmune risk, additional studies are needed to better evaluate these relationships, particularly for understudied autoimmune conditions. Future research should include larger longitudinal studies and studies among more diverse populations to elucidate the temporal relationships between exposure-outcome pairs and to identify potential population subgroups that may be more adversely impacted by immune modulation caused by exposure to these chemicals.

Whole-body aging mediates the association between exposure to volatile organic compounds and osteoarthritis among U.S. middle-to-old-aged adults

BACKGROUND

Humans are constantly exposed to various volatile organic compounds (VOCs) because of their widespread sources and characteristic of easy evaporation. Existing evidence regarding the association between VOC exposure and osteoarthritis (OA) risk is limited.

PURPOSE

This study aimed to investigate the associations between individual urinary VOC metabolites (VOCMs) and the VOCM mixture, representing internal exposure levels of VOCs, with prevalent OA risk and to explore the mediating effect of aging and oxidative stress (OS) in these associations.

METHODS

Data from the National Health and Nutrition Examination Surveys 2005-2020 were analyzed. Weighted generalized linear regression was employed to explore the associations between individual VOCMs and OA risk, as well as aging and OS biomarkers. A five-repeated ten-fold cross-validation elastic net model was used to identify critical VOCMs for the weight quantile sum (WQS) analysis, which was performed to explore the VOCM mixture and OA risk association. Parallel and serial mediation analyses were conducted to identify the potential mediators and mediation pathways.

RESULTS

This study included 6578 American adults aged ≥40 years, among whom 1052 (16.0 %) individuals reported prevalent OA. Urinary levels of N-acetyl-S-(benzyl)-L-cysteine, mandelic acid and phenylglyoxylic acid were positively associated with OA risk. Eleven VOCMs with nonzero coefficients were identified and included in the WQS analysis, and results revealed an average increase of 24.4 % in OA risk (OR = 1.244, 95 % CI: 1.041, 1.486) per one-quantile increment in the VOCM mixture. Two aging biomarkers, phenotypic age and biological age, parallelly mediated the association between the VOCM mixture and OA risk, with mediation effect proportions of 9.0 % and 16.4 %, respectively.

CONCLUSIONS

Exposure to VOCs is associated with an increased OA risk in middle-to-old aged American adults. The mediating effect of aging contributes to the association between co-exposure to VOCs and OA risk. Further prospective studies are required to substantiate these findings.

Engineered Stone Fabrication Work Releases Volatile Organic Compounds Classified as Lung Irritants

Engineered stones are often characterized for their crystalline silica content. Their organic composition, particularly that of the emissions generated during fabrication work using hand-held power tools, is relatively unexplored. We forensically screened the emissions from dry-cutting 12 engineered stone products in a test chamber for their organic composition by pyrolysis-gas chromatography-mass spectrometry (GC-MS) plus selected traditional capture and analysis techniques. Phthalic anhydride, which has a Respiratory Sensitization (RSEN) Notation by the American Conference of Governmental Industrial Hygienists (ACGIH), was the most common and abundant compound, at 26-85% of the total organic composition of engineered stone emissions. Benzaldehyde and styrene were also present in all twelve samples. During active cutting, the predominant volatile organic compound (VOC) emitted was styrene, with phthalic anhydride, benzene, ethylbenzene, and toluene also detected. These results have important health implications as styrene and phthalic anhydride are irritants to the respiratory tract. This study suggests a risk of concurrent exposure to high levels of respirable crystalline silica and organic lung irritants during engineered stone fabrication work.

Volatile organic compounds: A proinflammatory activator in autoimmune diseases

The etiopathogenesis of inflammatory and autoimmune diseases, including pulmonary disease, atherosclerosis, and rheumatoid arthritis, has been linked to human exposure to volatile organic compounds (VOC) present in the environment. Chronic inflammation due to immune breakdown and malfunctioning of the immune system has been projected to play a major role in the initiation and progression of autoimmune disorders. Macrophages, major phagocytes involved in the regulation of chronic inflammation, are a major target of VOC. Excessive and prolonged activation of immune cells (T and B lymphocytes) and overexpression of the master pro-inflammatory constituents [cytokine and tumor necrosis factor-alpha, together with other mediators (interleukin-6, interleukin-1, and interferon-gamma)] have been shown to play a central role in the pathogenesis of autoimmune inflammatory responses. The function and efficiency of the immune system resulting in immunostimulation and immunosuppression are a result of exogenous and endogenous factors. An autoimmune disorder is a by-product of the overproduction of these inflammatory mediators. Additionally, an excess of these toxicants helps in promoting autoimmunity through alterations in DNA methylation in CD4 T cells. The purpose of this review is to shed light on the possible role of VOC exposure in the onset and progression of autoimmune diseases.

Relationship between styrene exposure and prolactin secretion in human and animal studies: A systematic review

Styrene is widely used in industrial applications. Inhalation exposure occurs in the industry. Some studies indicated that serum prolactin concentrations increased after exposure to styrene, while other studies found no change. In this systematic review, the search was done with the keywords styrene and prolactin in the PubMed, Science Direct, Web of Science and Scopus databases, regardless of the publication period. 118 studies were obtained and only seven articles were finally selected according to exclusion and inclusion criteria. The effect of styrene on prolactin secretion was selected in both human and animal studies. The increased response was seen in inhalation exposures. Subcutaneous exposure has no significant effect on prolactin levels. The observed responses were both dose-dependent and gender-dependent. Changes in serum prolactin were more frequent in women compared to exposed men. Dopamine depletion was not observed in all studies, so more tests on laboratory animals are necessary to clarify the possible mechanism.

Airborne pollutants as potential triggers of systemic autoimmune rheumatic diseases: a narrative review

The pathogenesis of systemic autoimmune rheumatic diseases (SARDs) is complex and remains insufficiently understood. It is commonly accepted that both intrinsic and extrinsic environmental factors interact to induce a self-reactive immune response. Case reports and observational studies have revealed an association between SARDs and specific airborne environmental factors, but the heterogeneity of the published studies hampers clear conclusions. The aim of this review is to provide an overview of the available epidemiological evidence on the relationship between airborne pollutants and SARDs. We performed a narrative review using the PubMed database. Observational studies have shown significant associations between airborne pollutants and SARDs. Cigarette smoking is strongly associated with the development of rheumatoid arthritis (RA) while the association between cigarette smoke and the development of other SARDs remains controversial. For decades, silica exposure has been linked to systemic sclerosis (SSc), RA and systemic lupus erythematosus (SLE). There is also strong evidence for a link between solvents and SSc. Recent observations even suggest that ambient air pollution is associated with the development of SARDs. Some studies have shown associations between asbestos, organic dust, metals and pesticides and SARDs, but more studies are needed to confirm these findings. Increasing evidence has linked airborne pollutants to SARDs. Although more studies are needed to understand the potential mechanisms by which these environmental agents contribute to disease pathogenesis, awareness of the link between environmental agents and SARDs is important to recognize and prevent work-related and environmentally induced diseases.

Environment and Lifestyle: Their Influence on the Risk of RA

Background: Rheumatoid arthritis (RA) is a complex disease in which environmental agents are thought to interact with genetic factors that lead to triggering of autoimmunity. Methods: We reviewed environmental, hormonal, and dietary factors that have been suggested to be associated with the risk of RA. Results: Smoking is the most robust factor associated with the risk of RA, with a clear gene–environment interaction. Among other inhalants, silica may increase the risk of RA in men. There is less evidence for pesticides, pollution, and other occupational inhalants. Regarding female hormonal exposures, there is some epidemiological evidence, although not consistent in the literature, to suggest a link between hormonal factors and the risk of RA. Regarding dietary factors, available evidence is conflicting. A high consumption of coffee seems to be associated with an increased risk of RA, whereas a moderate consumption of alcohol is inversely associated with the risk of RA, and there is less evidence regarding other food groups. Dietary pattern analyses (Mediterranean diet, the inflammatory potential of the diet, or diet quality) suggested a potential benefit of dietary modifications for individuals at high risk of RA. Conclusion: To date, smoking and silica exposure have been reproducibly demonstrated to trigger the emergence of RA. However, many other environmental factors have been studied, mostly with a case-control design. Results were conflicting and studies rarely considered potential gene–environment interactions. There is a need for large scale prospective studies and studies in predisposed individuals to better understand and prevent the disease and its course.