Living in a developed country, such as the United States, means that most of us have the luxury of using cleaner fuels, like natural gas, to heat our homes and cook our food. People living in low- and middle-income countries are not so lucky. Upward of three billion people worldwide still use smoky solid fuels such as wood, crop wastes, charcoal, coal, and animal dung in open fires and leaky stoves to heat their homes and cook. Since women and children spend a lot of time near these motley ovens and heaters, they take on the highest risk from indoor air pollution.

In a recent study, published in the American Heart Association's journal Circulation, researchers examined long-term exposure to household air pollution among people living in northeastern Iran — a region famous for having the highest rates of esophageal cancer in the world. Their findings show that long-term exposure to indoor air pollution could be a significant risk factor for heart attacks and death while burning cleaner fuels is linked to lower risk for cardiovascular death.

"We know that smoking tobacco products and outside air pollution are linked to heart disease death," said Dr. Sumeet Mitter, lead researcher and cardiovascular disease fellow at Northwestern University's Feinberg School of Medicine in Chicago, in a statement. "Our study, using exposure history and time, is the first to find a significant and independent increased risk for all-cause, total cardiovascular disease and heart attack deaths due to increasing lifetime exposures to household air pollution from kerosene or diesel burning."

Mitter and his colleagues analyzed exposure to indoor air pollution among 50,045 people living in northeastern Iran between 2004 and 2008. Sources of pollution within the home included burning kerosene, wood, diesel, cow dung, and natural gas. Each participant was asked to complete a lifestyle questionnaire that gauged their exposure to household pollution caused by cooking and heating throughout their lives. Researchers also took blood pressure and other measurements indicative of health.

People who reported burning kerosene or diesel had a 6 percent higher risk for dying from all-cause mortality throughout the next 10 years. They were also 11 percent more likely to die as the result of a cardiovascular event and 14 percent more likely to suffer from ischemic heart disease. People who used natural gas, on the other hand, had a 6 percent lower risk for cardiovascular death compared to those depending on other fuels. Half of the world’s population lives in poverty and burns fuels for lighting, cooking, and heating.

"Since heart disease is the leading cause of death worldwide, it is important for physicians to assess for a number of modifiable risk factors for heart disease, including household air pollution, so that they can intervene and help patients and communities worldwide transition to cleaner burning fuels and reduce the risk for cardiovascular death," Mitter added. "The next step would be to create a study to measure particulate matter to better establish a dose-response relationship between household air pollution and cardiovascular death.”

An estimated 4.3 million people around the world die each year due to an illness caused by household air pollution, according to the World Health Organization. One quarter of premature deaths caused by stroke, 17 percent of premature lung cancer cases, and half of all pneumonia deaths among children younger than 5 are linked to poor indoor air quality. Luckily, there are options for reducing indoor air pollution.

Although burning solid fuels inside the home is uncommon in developed countries, indoor air pollutants can be found in American homes. Asbestos has been banned from widespread use in the U.S., but some still remains in older homes in insulation material, textured paint, and floor tiles. Formaldehyde is not banned and can be found in common household cleaning products.

The Environmental Protection Agency recommends testing homes for radon, a natural radioactive gas that can cause lung cancer. These inexpensive tests are the most effective way to identify this odorless and tasteless gas. We can also reduce the spread of mold and keep our homes smoke-free. Other helpful steps include making sure ventilation systems are working properly and installing carbon monoxide alarms. Research has shown that plants scattered throughout homes and offices can improve air quality via photosynthesis and even increase productivity.

Source: Islami F, Vedanthan R, Mitter S, et al. Household Fuel Use and Cardiovascular Disease Mortality Golestan Cohort Study. Circulation . 2016.