Exposure to biomass fuel smoke is a health concern in Sri Lanka!

Exposure to biomass fuel smoke is a health concern in Sri Lanka!

Lay summary of the thesis submitted to Faculty of Graduate Studies, University of Sri Jayewardenepura for the award of MPhil degree in Physiology 2020.


Firewood and plant materials are commonly used as cooking fuel in Sri Lanka. These are called “biomass fuel”. The burning of biomass fuel produces smoke containing air pollutants. These air pollutants cause damages to airways leading to respiratory diseases. Women, are the cooks of Sri Lankan households. Thus, they are most likely to be exposed to biomass fuel smoke.

We conducted this study in 2017-2018 to assess respiratory functions and associated factors of women (n=363) exposed to biomass fuel smoke (WBMF). The parameters were compared with a group of women from the same area using liquid petroleum gas for cooking. Base line data, and respiratory symptoms were determined by a questionnaire. All women were clinically examined to determine respiratory signs. We used spirometry, levels of Fractional exhaled Nitric oxide (FENO) and levels of exhaled Carbon monoxide (eCO) to assess respiratory functions. These are novel and reliable tests for assessing respiratory health. Reduced spirometry parameters indicate poor respiratory functions. FENO and eCO are exhaled breath biomarkers. Increased levels of FENO and indicate airway inflammation and increased eCO levels indicate oxidative stress, both are hallmarks of many lung diseases.


Our study showed that WBMF were older and of poor socioeconomic status. They spent more time cooking with an average of 6 hours per day. They had a higher mean biomass fuel exposure index of 172 hours-years. None of them cooked in un-partitioned areas or open fires or used animal dung. The majority of their kitchens had windows/ grills (84%) and a chimney (78%). Only 13% used three stone cookstoves and others used commercially available clay cookstoves. All cookstoves were placed above the ground level. WBMF had a higher prevalence of respiratory symptoms (33%). Increased duration of cooking, having an outdoor kitchen, poor ventilation in the kitchen and not using a blowpipe were associated with an increased risk of respiratory symptoms of women using biomass fuel.


WBMF had poor respiratory functions and increased airway inflammation and oxidative stress (as assessed by eCO). Further, statistical analysis showed, that use of biomass fuel was a significant contributor to poor respiratory functions of these women when adjusted for other confounders. Among WBMF, increased biomass fuel smoke exposure index, not having a chimney in the kitchen, poor ventilation in the kitchen, using a three-stone cookstove and not using kerosene with wood were associated with poor respiratory functions and increased airway        inflammation. Obstructive airway disease (5.6%), small airway disease (6.1%) and airway inflammation and oxidative stress (74.7%) were more prevalent among WBMF. Among WBMF, increased biomass fuel exposure index and poor ventilation were associated with increased risk of obstructive airway disease, airway inflammation and oxidative stress.

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Our study provided promising scientific evidence for increased respiratory symptoms, poor respiratory functions and increased airway inflammation and oxidative stress among WBMF in Sri Lanka. Further, it described the significant correlates for poor respiratory health among WBMF in the Sri Lankan context. However, we noticed that the prevalence of respiratory symptoms and impaired respiratory functions reported in our study was less compared to what was reported in most of the other countries. The unique sociocultural features that have been practised in Sri Lanka over generations could be influencing the exposure to biomass fuel smoke and thus modifying the pulmonary responses of this population. The good ventilation features in the kitchens reduce the peak hours of exposure to biomass fuel smoke. The use of improved cookstoves that are thermally efficient generates fewer air pollutants. Placing the cookstove above the ground level helps the vertical dispersion of air pollutants. Firewood emits comparatively fewer pollutants than animal dung. The use of a blowpipe aerates the cookstove well-providing oxygen for complete combustion. Kerosene is more thermally efficient and adding kerosene to firewood facilitates complete combustion. Chopping and drying firewood provide small pieces and less moisture that favours complete combustion.

We recommend shifting to cleaner fuel to prevent the deterioration of the respiratory functions of women. However, this could be challenging due to their poor socioeconomic status. If the use of biomass fuel for cooking is continued, we recommend having good ventilation holes in the kitchen such as windows and a chimney, regular cleaning of the chimney, use of improved cookstoves and improved cooking devices and pot lids further assist to decrease the exposure to biomass fuel smoke. Measurement of eCO can be used as a reliable technique in screening respiratory health in resource-poor settings. We recommend establishing a team of experts to conduct respiratory health screening and awareness programmes among WBMF in coordination with the public health services of the country to decrease the health effects caused by exposure to biomass fuel.