Solid Fuels Used for Cooking and Heating Pose Cardiovascular and Mortality Risks

People living in rural areas who burn wood or charcoal for cooking or to heat their homes are at higher risk for cardiovascular disease and death than those who have access to clean fuels such as gas or electricity, according to a large study from China.

“The exact mechanisms through which solid fuel use may contribute to mortality risk are not well understood,” write investigators led by Kuai Yu, MD (Huazhong University of Science and Technology, Wuhan, China). Gaseous pollutants and particulate matter released when solid fuels are burned may be contributing to cardiac autonomic dysfunction and atherothrombosis, they note.

“Household air pollution is a very under-recognized source of ambient air pollution,” said Rufus D. Edwards, PhD (University of California, Irvine), who was not involved in the study. “People tend to look at industry or transportation, perhaps based on concerns in the industrialized countries, [but] the contribution when you breathe smoke indoors is huge.”

This is half the world’s population we’re talking about that use solid fuels. In terms of global disease, this is a major issue. Rufus D. Edwards

In an interview with TCTMD, Edwards added that since the proximity of the pollution source to the person is a major factor in increasing risk, the study also highlights the importance of a simple measure that is often overlooked—ventilation. Individuals in the study who used ventilation when cooking—a chimney or extractor fan/hood—had lower risks than those who did not.

“It’s good to see that it translates into measurable decreased risk in this study,” Edwards said.

According to Yu and colleagues, that finding may have important public health significance “because improving ventilation is often a more feasible alternative to clean fuel substitution and should be promoted in lower-income countries, which might reduce the disease risks associated with solid fuel use,” they write in their paper published online April 3, 2018, ahead of print in JAMA.

Switch to Clean Fuel is Best

The study included 271,217 adults from five rural areas of China who participated in a baseline health survey of sociodemographic characteristics, lifestyle behaviors, household air pollution exposures, and personal medical history. None had a diagnosis of cardiovascular disease at the time. Participants were then randomly selected for a resurvey.

For the study, coal and wood were considered solid fuels, while gas and electricity were considered clean fuels. Researchers measured the duration of exposure to fuels for cooking and heating based on detailed responses from the survey, including how many times per week the participants cooked, and the length of time they lived in residences where primarily solid fuels were used.

Over a mean of 7.2 years of follow up, those who used solid fuel had a higher risk of both cardiovascular mortality (HR 1.20; 95% CI 1.02-1.41) and all-cause mortality (HR 1.11; 95% CI 1.03-1.20) compared with participants using clean fuel sources. The findings were consistent across subtypes of cardiovascular disease and were similar for solid fuel used for heating. Risks increased in proportion to the length of time exposed to solid fuels and were magnified in individuals who reported a combination of smoking and exposure to solid fuels.

The researchers also found that participants who reported having switched from solid to clean fuel sources for cooking and/or heating had significantly lower risks of cardiovascular mortality and all-cause mortality.

Edwards said while cleaner-burning fuels are safer and there has been progression globally in trying to make the shift, a variety of barriers exist depending on locale. These may include supply constraints, long travel to obtain clean fuel, cost, and other issues specific to individual countries and populations.

“This is half the world’s population we’re talking about that use solid fuels,” he observed. “In terms of global disease, this is a major issue.”