Cooking with wood or coal can add extra aroma and flavor to food. But, when it comes to health perspective, cooking with coal or wood is associated with an increased risk of significant eye diseases.
About three billion people worldwide live in households that regularly burn wood, coal, or other solid fuels to cook their food. Solid fuels emit very high pollutants, especially very small particles that can penetrate the eyes, leading to several possible injuries caused by the flickering flames.
Numerous studies have suggested a possible link between cooking with solid fuels and an increased risk of cataracts in women. However, it remains unclear whether the same is the reason for major eye diseases, such as conjunctivitis, keratitis, and glaucoma.
A new study from the University of Oxford‘s Nuffield Department of Population Health (NDPH) and the Chinese Academy of Medical Science and Peking University, Beijing, analyzed data from almost half a million Chinese adults in China Kadoorie Biobank. The study includes almost half a million participants in China.
Scientists asked them about their cooking habits through a questionnaire. They then tracked their hospital admissions of significant eye diseases through linkage to health insurance records. They found a clear association between cooking with wood or coal and an increased risk of substantial eye diseases leading to blindness.
Over the ten-year follow-up period, there were 4,877 cases of conjunctiva disorders, 13,408 cataracts, 1,583 disorders of the sclera, cornea, iris, and ciliary body (DSCIC), and 1,534 cases of glaucoma among study participants.
The results show that:
- Long-term use of solid fuels for cooking was associated with 32%, 17%, and 35% higher risks of the conjunctiva, cataracts, and DSCIC, respectively, compared with those who cooked using clean fuels;
- There was little difference in risk between the different types of solid fuel used (for instance, coal versus wood);
- There was no association between long-term use of solid fuels and an increased risk of glaucoma;
- Individuals who switched from using solid to clean fuels for cooking had smaller elevated risks (over those who had always used clean fuels) than those who did not switch. People who switched had 21%, 5%, and 21% higher risk for conjunctiva, cataracts, and DSCIC, respectively.
Dr. Peter Ka Hung Chan, research fellow in the Nuffield Department of Population Health, University of Oxford, and lead author of the study, explained these findings: “The increased risks may be caused by exposure to high levels of fine particulate matter (PM2.5) and carbon monoxide, which can damage the eye surface and cause inflammation.”
Professor Zhengming Chen, Professor of Epidemiology and Director of China Programmes at the Nuffield Department of Population Health, University of Oxford, and a senior author for the study, said, “Among Chinese adults, long-term solid fuel use for cooking was associated with higher risks of not only conjunctiva disorders but also cataracts and other more severe eye diseases. Switching to clean fuels appeared to mitigate the risks, underscoring the global health importance of promoting universal access to clean fuels.”
Professor Liming Li from Peking University and a senior author for the study, said, “Our study adds yet another piece of evidence to support governmental efforts to facilitate fuel transition, and the general public should be informed about the potential risks of eye diseases, some of which are highly disabling, related to solid fuel use.”
Commenting on the research, Imran Khan, Director of Programme Strategy & Development at international development organization Sightsavers, commented: “Sightsavers’s vision is of a world where no one is blind from avoidable causes and the study highlights that eye problems result from several factors, not just the traditional causes we commonly think of.”
“Environmental factors and societal traditions, such as cooking with solid fuel, can have a big effect on eye health and show the need to work across all levels of health systems to improve outcomes. From government to communities, it’s important to raise awareness of eye conditions, reduce these avoidable causes, and provide accessible health services.”
- Ka Hung Chan,Mingshu Yan et al. Long-term solid fuel use and risks of major eye diseases in China: A population-based cohort study of 486,532 adults. DOI: 10.371/journal.pmed.10093716