cancer risk from wood burning

 How one German village exemplifies the cancer risk from wood burning.

Residential heating with wood or coal can lead to significant air pollution, even in rural communities, researchers say.

In autumn 2018, a shipping container full of air pollution measurement equipment arrived in the centre of the small German village of Melpitz.

Dr Dominik van Pinxteren of the Leibniz Institute for Tropospheric Research explained the reason for their investigation: “We were concerned that wood burning could be an important source of particle pollution in small villages, but these areas are not adequately covered by official air quality monitoring networks.”

Located in Saxony and surrounded by agricultural land and pasture, Melpitz is home to about 200 people. They live in 63 houses, mostly heated by oil or wood central heating, with a small number of homes using coal.

The researchers found that wintertime particle pollution in the village was often double that in the nearby fields. The air was worst at the weekends when smoke from stoves added to the pollution mixture. For the villagers, the risk from the extra particle pollution was estimated to be half as high as their risk of death in a traffic accident.

The air in Melpitz contained cancer-causing polycyclic aromatic hydrocarbons, which are persistent pollutants in wood and coal smoke. The cancer risk from these exposures was similar to that in major European cities, including Athens and Florence.

Using an indoor wood stove or fireplace increases women’s risk of developing lung cancer by 43% compared with those that do not use wood heating, according to a US study.

In the UK, one in 13 men and one in 15 women born after 1960 are expected to be diagnosed with lung cancer during their lifetimes. In the US it is one in 16 men and one in 17 women.

The US study found that more frequent use of indoor wood heating led to greater risk. For example, people who used their wood burner on more than 30 days a year had a 68% increased lung cancer risk compared with people who did not burn wood.

The results come from the Sister Study, which tracks the health of 50,000 US women who had sisters with breast cancer.

Dr Suril Mehta, from the US National Institute of Environmental Health Sciences and first author of the new study, said: “The Sister Study was designed to better understand genetic and environmental risk factors for breast cancer, but it is also equipped to evaluate other health outcomes in women. Lung cancer is the leading cause of cancer-related death among US women. It accounts for roughly one in five cancer-related deaths in the US.”

Globally, tobacco smoking is the biggest risk factor for lung cancer, but not the only one. This was reflected in the Sister Study findings. The latest results come after tracking the women’s health for an average of 11 years. During this time 347 participants were diagnosed with lung cancer; 289 were current or former tobacco smokers and 58 were non-smokers.

Having allowed for income and other factors that could have affected the women’s health there were clear differences in the risk of developing lung cancer in those that heated their homes with wood compared with those that did not. This extra risk was seen in both tobacco smokers and those who had never smoked.

In the UK, only 4% of homes that use solid fuel rely on it as their only heating source. Similarly, the Sister Study homes primarily used gas or electricity for heating, with wood being mainly a secondary or tertiary heating source.

Mehta said: “Our study provides evidence that even occasional indoor wood burning from stoves and fireplaces can contribute to lung cancer in populations where indoor wood burning is not the predominant fuel source for cooking or heating inside the home.”

Prof Fay Johnston from the Menzies Institute for Medical Research, Tasmania, who was not involved in the US research, said: “The new results from the Sister Study provide strong evidence of the risk of living in homes heated by wood combustion. Even relatively low usage was associated with an increased risk of lung cancer.”

She added: “The message for policymakers and the public is clear. Wood heater smoke is not safe. Interventions to reduce exposure in homes and neighbourhoods should be a priority.”

The research adds to growing evidence of the risk of cancer from wood smoke. In October 2006, the International Agency for Research on Cancer classified wood smoke as probably carcinogenic to humans. Though far smaller than the Sister Study and using a different methodology, an international study from 2010 found increased lung cancer risk in people that used wood and coal heating compared with those that did not.

Mehta said: “Wood smoke, from using wood-burning appliances indoors, may contain substances such as benzene, 1,3-butadiene, polycyclic aromatic hydrocarbons, and other hazardous air pollutants which are known or suspected to cause lung cancer.”

In the Sister Study, gas or propane heating in stoves and fireplaces was also associated with an increased lung cancer risk, but this was far smaller than that from wood burning.

An earlier report from the Sister Study concluded that air pollution from indoor wood burning was also a widespread and potentially modifiable risk factor for breast cancer.

Van Pinxteren said the findings were significant: “Residential heating with wood can lead to significant pollution, even in small villages. The emissions take place where people are living. Everyone – from young to old – is inevitably affected because we all breathe the same air.”

Recent data from a village in Slovenia and a study of three small towns in Ireland show that the situation in Melpitz is likely to be replicated in many rural areas. This includes the UK, where the proportion of rural homes that burn wood and coal is twice that in cities.

Another new study has looked at health impacts inside Irish homes that burn wood, coal and peat – most of them in rural towns and villages. Elderly people who heated their homes with open fires had a 2.3 times greater risk of respiratory disease compared with those that used closed stoves. This impact was on top of the effects of tobacco smoking, childhood lung problems and dampness in the home, all of which were important contributors in their own right.

As a group, people with central heating also had an increased risk. This was thought to be due to the large number of Irish homes with central heating who also used open fires for secondary heating.

An earlier study in Ireland also linked indoor smoke from open fires to accelerated cognitive decline, and US a study found that heating a home with a wood stove or fireplace increased the risk of lung cancer by 43%.

There is clearly an urgent need for better data, and for actions to reduce exposure to wood and coal pollution in rural communities across Europe.

Tessa Bartholomew-Good, from the charity Global Action Plan, said: “Public awareness of the harms of domestic burning is still too low. The first step should be to highlight these harms to consumers. For example, introducing health warning labels for both stoves and solid fuels like wood, coal and alternative fuel, similar to the ways used to land the public health harms of smoking.”