Air pollution linked to fatty liver disease, lung cancer

Air pollution linked to fatty liver disease, lung cancer

Two recent studies have identified links between ambient air pollution and disease, highlighting the need for populations at risk to be aware of the air quality in the areas where they live and to minimize their exposure to it. pollution to the extent possible.

The incidence of metabolism-associated fatty liver disease (MAFLD), formerly known as non-alcoholic fatty liver disease (NAFLD), has increased steadily since the 1980s, currently affecting a quarter of the world’s population and the majority of patients with the disease. adult fatty liver disease. Diabetes. With the potential to progress to end-stage liver diseases such as cirrhosis and liver cancer, liver transplantation, and liver-related deaths, MAFLD reached 40% of the population in Asia between 2012 and 2017.

Animal studies have shown that breathing air pollutants can increase the risk of MAFLD; for example, exposure to fine particles can trigger a non-alcoholic steatohepatitis (NASH) -like phenotype, alter hepatic glucose metabolism, and promote hepatic fibrogenesis. But with limited epidemiological evidence for this association, researchers led by Sichuan UniversityDr Xing Zhao set out to improve their understanding of the effects of air pollution on human health.

Investigators conducted an epidemiological study on the potential role of ambient air pollution in the risk of MAFLD in approximately 90,000 adults in China based on the China Multi-Ethnic Cohort (CMEC) baseline survey. , a prospective cohort that recruited nearly 100,000 participants in southwest China from 2018 to 2019. CMEC collected information on the participants, including socio-demographic data, lifestyle habits, and health-related backgrounds through verbal interviews, then assessed anthropometric data, biological samples (blood, urine and saliva) and imaging data.

Researchers have found that long-term exposure to ambient air pollution may increase the risks of MAFLD, especially in men, smokers and alcohol drinkers, and those who follow a high-fat diet. . Their results, published in the Journal of hepatology, have found that unhealthy lifestyle behaviors and excessive fat accumulation in the abdominal area can also exacerbate the harmful effects. The investigators thus propose that air pollution be recognized as a modifiable risk factor for MAFLD.

“Our findings add to the growing evidence for the detrimental effects of environmental pollution on metabolic function and associated organs,” said Dr Zhao and his co-investigators. “However, physical activity does not appear to alter the associations between air pollution and MAFLD. We suggest that future studies explore whether the timing, intensity and form of physical activity may mitigate the effects. harmful air pollution.

Meanwhile, researchers from Nanyang Technological University, Singapore (NTU Singapore) and Chinese University of Hong Kong have linked increased air pollution to a slight increase in cases of pulmonary adenocarcinoma (LADC) – a type of cancer in which research suggests genetic, environmental, and lifestyle factors play a role . The team’s study, published in the journal Atmospheric environment, also concluded that lower overall tobacco consumption globally is statistically linked to a lower number of people who contract pulmonary squamous cell carcinoma (LSCC), which is often linked to a history of smoking.

The study showed that a concentration of 0.1 μg / m3 The increase in black carbon (soot) in the Earth’s atmosphere is associated with a 12% increase in the incidence of LADC globally. Carbon black is a pollutant classified as PM2.5 (airborne particulate matter less than 2.5 m in diameter), and the research team found that it increased globally by 3.6 g / m3 annually from 1990 to 2012. The incidence of LADC is particularly significant in Asia, where black carbon emissions (11.9 μg / m3/ year) and sulfate (35.4 μg / m3/ year) have increased.

“In our study, we were able to determine that the worldwide increase in pulmonary adenocarcinoma is likely associated with air pollution,” said study director Professor Joseph Sung, senior vice president of NTU (Health and Life Sciences). “Over the past several decades, it has still not been clear why we are seeing more women and more non-smokers developing lung cancer around the world. Our study highlights the importance of environmental factors in the causation of specific types of lung cancer.

The link between the pollutant and the incidence of LADC was found to be stronger in women than in men. Overall a 0.1 μg / m3 the annual increase in carbon black was associated with a 14% increase in LADC in women, compared to 9% in men. The relationship between air pollutants and LADC also varied across continents; in North America, a 0.1 μg / m3 The increase in carbon black was linked to a 10% increase in LADC cases, compared to 7% in Europe.

Meanwhile, a 1% drop in smoking prevalence has been associated with a 9% drop in the incidence of LSCC globally, with the number of smokers globally declining by nearly 6% from 1990 to 2012. However, a positive association between smoking and LSCC was demonstrated for women in Asia, North America and Oceania, where a 1% increase in the number of smokers was associated with a 12% increase in cancer in women. these geographic regions. Scientists explained that despite a lower overall percentage of smokers in the world, there were more smokers in the world due to massive population growth from 1980 to 2012, causing the number of female smokers to increase by 7%.

“The results of this study should warn us that air pollution should be better controlled to protect health and prevent premature death from lung cancer or related diseases, especially in populations who live near urban areas, which are known to experience high levels of pollutant emissions. “said Professor Sung.

“Our results underscore the urgent need for further research into how pollutants such as carbon black and sulfate lead to the development of pulmonary adenocarcinoma, and for international leaders and experts to consider mitigation strategies. air pollution. “

Associate Professor Steve Yim, the study’s first author, added, “While national environmental regulators routinely measure and report fine particle levels, our results underscore the importance of measuring individual types. particles, in particular carbon black. The information would be useful in formulating effective emission control policies, supporting sustainable development policies.

The team plans to conduct further research to study the functions of carbon black and sulfate in the development of LADC, which could lead to new studies to fight the resurgence of cancer. The team also hopes to explore other pollutants that could be linked to lung cancer.

Image Credit: © stock.adobe.com / au / lukyeee_nuttawut

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