Woodsmoke exposure and health: from natural experiments to controlled experiments

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Date/Time
Date(s) - 2017/05/26
12:30 pm - 1:30 pm

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Speaker: Dr. Curtis Noonan (About)

The global burden of disease attributed to household air pollution is primarily driven by exposures to smoke from burning of biomass fuels for cooking and heating in developing countries. However, wood-burning is also an importance source of ambient and household air pollution in developed countries, particularly in rural communities. Intervention strategies for reducing the health burden from exposure to biomass combustion smoke in developed countries include community-level and household-level approaches, but contemporaneous evaluations of health impacts following these intervention strategies have been limited. We review here a selection of such studies, ranging from natural experiments to controlled experiments. Two natural experiment studies tracked population-level health outcomes during community-wide strategies to reduce ambient biomass combustion exposures. In the small rural community of Libby, Montana, USA over 1,100 woodstoves were replaced predominantly with improved technology wood burning heaters. A four year survey-based study tracked parent reported respiratory symptoms and conditions among school children, showing significant percent reductions in reported frequency per 5 µm/m3 reduction in ambient PM2.5 for wheeze (27%), cold (25%), bronchitis (55%), flu (52%), and throat infection (45%). In Launceston, Tasmania, Australia substantial mortality changes were observed from the period before (1994-2000) and after (2001-07) the government-coordinated fuel switching effort. Investigators demonstrated significant reductions in male, but not female, mortality. Two controlled experimental trials tracked individual health outcomes following household-level interventions. A filter intervention crossover study examined changes in microvascular endothelial function as measured by reactive hyperemia index (RHI) as well as changes in serum and urine markers of oxidative stress and inflammation. The use of the filter was associated with significantly higher mean percent measures of RHI (9.4%) and significantly lower mean percent measures of the inflammatory marker C-reactive protein (32.6%). Finally, a randomized trial of filter interventions compared to placebo control was conducted among children with asthma living in a woodstove home. No improvements in quality of life measures were observed, but the intervention group did show improvements in diurnal peak flow variability, an indicator of airway hyper-reactivity. Collectively, these studies demonstrate some beneficial health effects following wood stove interventions, but these investigations are few and varied with remaining questions and no repeat observation for any particular outcome or approach.

 

 

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6 Comments

  1. Profile photo of Dr Dorothy L Robinson
    Reply

    Question: Launceston’s efforts to reduce PM2.5 pollution by switching to non-polluting heating were much more successful and cost-effective than Libby’s program, in which the majority of old stoves were replaced with new ones. The final report in 2015 evaluating British Columbia’s woodstove exchange program noted that over $2.2 million had been spent, without achieving any clear reduction in woodsmoke pollution in BC.

    Fay Johnston’s WSRN presentation last year concluded that the only successful intervention in Tasmania was to remove wood heaters. Improved heater emissions standards, education on correct operation and retrofitting catalyst technology were of questionable benefit – http://wsrn.science/wp-content/uploads/sites/2/2016/05/FayJohnston.pdf

    Thanks to the recent efficiency improvements, modern heater air-conditioners are cheaper than buying a wood heater, cause less global warming (zero in households that use green power) and have lower running costs than buying firewood except in climates with sustained temperatures more than 10 degrees below freezing. Given the much greater benefits and success of replacing wood stoves with non-polluting heating, should future woodsmoke programs follow the example of the SF Bay Area’s ‘Spare the Air – Cool the Climate’ that “To reduce emissions of particulate matter (PM) and black carbon, we will also need to eliminate wood burning.”?

  2. Profile photo of Dr Dorothy L Robinson
    Reply

    Here’s an example of a subsidy scheme for Lower Elwha Klallam Tribe, Port Angeles, Washington, showing how they cut energy costs by installing ductless heat pumps. One tribal elder reports being so pleased with the results and that the heat pump is saving so much money and keeping the house so warm and dry that he hasn’t used his wood stove all winter – https://www.youtube.com/watch?v=u7LWX_jL1yI
    Does this suggest that it might be easier to overcome perceived barriers to replacing wood stoves with non-polluting heating than trying to reduce ambient PM2.5 pollution by upgrading wood stoves and persuade owners to operate them correctly?

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