Thailand medical study links air pollution to increased liver cancer mortality

Thailand Medical: Air Pollution and Liver Health in Thailand
A recent study conducted in Northern Thailand has drawn attention to the alarming correlation between air pollution, specifically particulate matter (PM2.5 and PM10), and an increased risk of liver cancer mortality. The research, led by a team from various prestigious institutions such as Chiang Mai University and the National Astronomical Research Institute of Thailand, has shed light on how air pollution may exacerbate liver cancer mortality. This Thailand Medical News report covers the study findings that were recently published in a peer reviewed journal.


Thailand medical study links air pollution to increased liver cancer mortality
 
The Study’s Background
Thailand has long struggled with high levels of air pollution, particularly in the northern region where crop burning and forest fires are common. Air pollutants like PM2.5 and PM10 - tiny particles that can be inhaled and absorbed into the bloodstream - are of particular concern. Once these particles enter the body, the liver, responsible for detoxifying the blood, can be severely affected.
 
The research highlights findings from a cohort study involving 10,859 liver cancer patients diagnosed between 2003 and 2018, with follow-up data extending through 2020. The researchers analyzed the effects of long-term exposure to air pollutants and examined how these might influence the mortality risk of liver cancer patients.
 
What the Research Found
The study found several significant factors that increased the risk of mortality for liver cancer patients:
 
-Metastatic Cancer Stage: Patients diagnosed at this advanced stage had the highest risk of mortality. In fact, the adjusted hazard ratio (aHR) was 3.57, meaning these patients were more than three times as likely to die compared to those in earlier stages.
 
-Male Gender: Men showed a slightly higher risk of mortality with an aHR of 1.10, while patients over the age of 60 had an aHR of 1.16.
 
-Smoking History: Patients who smoked also faced a higher risk, with an aHR of 1.16.
 
-Air Pollution: Exposure to air pollution, specifically PM2.5, showed a strong association with increased liver cancer mortality. A concentration of PM2.5 over 40 μg/m³ resulted in an aHR of 1.10, indicating a 10% higher risk of death for those exposed to this level of pollution.
 
Implications for Thailand
Thailand has one of the highest liver cancer rates in the world, second only to Mongolia in Asia. The research found that environmental factors, particularly air pollution, might be playing a role in this high mortality rate. Thailand’s liver cancer incidence rate is expected to increase sharply by 2040, which raises concerns about how air pollution might influence future health tre nds.
 
Northern Thailand, where the study was conducted, experiences high levels of pollution due to crop-burning activities and forest fires, particularly in the dry season from January to April. These seasonal pollutants not only affect the lungs but, as this study suggests, may also impact the liver.
 
How Does Air Pollution Impact the Liver?
The liver plays a critical role in detoxifying harmful substances, including air pollutants. When pollutants like PM2.5 and PM10 enter the bloodstream, they can cause oxidative stress - an imbalance between free radicals and antioxidants in the body. This oxidative stress can lead to DNA damage, liver inflammation, and even promote the development of liver cancer. The study’s results reinforce earlier findings from research in Taiwan and California, where exposure to similar pollution levels significantly increased the risk of liver cancer mortality.
 
Study Design and Analysis
The cohort study was comprehensive, utilizing time-varying covariates to assess air pollution exposure levels over time. This means that instead of relying on a one-time measurement of pollution exposure, the researchers updated pollutant concentrations annually, providing a more accurate picture of long-term exposure.
 
The pollutants studied included PM2.5, PM10, nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), and ozone (O3). Of these, PM2.5 had the most significant impact on liver cancer mortality, with PM10 and CO also contributing but to a lesser extent.
 
Other risk factors such as age, gender, cancer stage, smoking, and alcohol history were also considered in the analysis. While air pollution had a significant impact, it’s important to note that these personal risk factors played an essential role in determining outcomes for the patients.
 
Survival Rates and Mortality Risk
The survival rates for liver cancer patients were grim, with an overall mortality risk of 68 deaths per 100 person-years of follow-up. Men and older individuals had a significantly higher mortality risk compared to women and younger patients. The median survival time for the patients was just 0.42 years, with the majority of deaths occurring within the first three years following diagnosis.

In areas with high PM2.5 levels, survival probabilities were notably lower. Patients residing in regions with PM2.5 concentrations above 40 μg/m³ had a survival probability of only 13% within three years after diagnosis.
 
Conclusions and Recommendations
The study underscores the need for policymakers to address the environmental factors contributing to liver cancer mortality in Thailand. Mitigating air pollution, particularly during the dry season when crop burning and forest fires worsen the air quality, is crucial to reducing liver cancer mortality rates.
 
While individual risk factors such as smoking, alcohol use, and early detection are important, the influence of environmental pollution should not be overlooked. The study calls for better monitoring of air quality in northern Thailand and for efforts to reduce exposure to harmful pollutants.
 
Furthermore, public health campaigns aimed at reducing smoking and alcohol consumption, along with initiatives to improve early cancer detection, could help improve survival rates for liver cancer patients in the region.
 
Final Thoughts
Liver cancer is a deadly disease, and the findings from this study highlight how environmental pollution can worsen outcomes for those diagnosed with the condition. As Thailand’s air quality continues to deteriorate due to forest fires and agricultural practices, addressing these issues becomes more critical than ever.

The study findings were published in the peer-reviewed journal: Frontiers in Public Health.
https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2024.1389760/full
 
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https://www.thailandmedical.news/news/thailand-medical-study-finds-that-long-term-air-pollution-exposure-disrupts-kynurenine-pathway-elevating-disease-risks