In Canada, minimum and maximum temperatures have increased over the last few decades, particularly in winter [1]. For instance, in southern Québec (south of the 49th parallel) average temperatures have increased by 0.5°C to 1.2°C based on an east-west trajectory [2]. These increases however, do not mean that climate warming is linear [3]. In fact, periods of intense cooling and severe storms are still predicted to occur. People will have to adapt appropriately, if only to prevent the health impacts of concern due to the cold [4, 5].

A winter adaptation strategy is the use of residential wood heating. In Canada, more than 3 million dwellings use it as the primary or secondary source of heat [6]. Furthermore, the popularity of this type of heating grew in Québec to the point that its penetration rate increased by approximately 60% between 1987 and 2000 while the number of dwellings increased by less than 20% [7]. The massive and prolonged power outages that occurred in the middle of winter during the ice storm of 1998 [8] are thought to have played a significant role in this increase. In fact, the Web site of the Department of Natural Resources of Canada highlights this extreme climatic event in referring to evolved wood burning techniques as a means of coping with the worst winter storms [9].

Residential wood heating is also one of the main causes of winter smog in Canada. This type of heating is in fact responsible for 29% of Canadian emissions of fine particulates – one of the two key components of smog and its main winter component [10] from anthropogenic sources [11]. This relative contribution of fine particulates to emissions is even higher in Quebec at 47% [12] compared to most jurisdictions using fossil fuels for power generation, because hydroelectricity accounts for 96% of electricity production in the province and a great many homes use electric heat as the main source of heating.

Moreover, among the approximately one hundred atmospheric pollutants in wood smoke, several are greenhouse gases, while others are precursors of tropospheric ozone – the other key component of smog [13]. Furthermore, human exposure to fine particulates and tropospheric ozone is of particular concern because there are still no established concentration thresholds below which these pollutants are known to be safe and not pose a human health risk [13]. Young children, the elderly and people with respiratory problems (e.g., asthmatics) or heart problems are the most vulnerable, while healthy people who are repeatedly exposed, such as users of combustion units and their neighbours may also be at risk [7, 14, 15]. Finally, a well-known relationship exists between the harmful effects of these atmospheric pollutants and the increase in the number of visits to emergency rooms, hospitalizations, health care costs, absenteeism, the reduction in the labour force participation rate, as well as premature death [16].

Clearly, the rise in popularity of residential wood heating is a public health concern [16]. And it will continue to grow should the supply and demand for this type of heating increase as extreme climatic events become more frequent and intense [1]. The aim of this study was to examine diverse perceptions and characteristics associated with wood heating through a survey carried out in 2005 in southern Québec, Canada [17] in the context of a research program aiming to propose climate change (CC) adaptation strategies that respect the environment as well as health and well-being.

This population survey on beliefs and adaptations about climate change, including residential wood heating, did not intend to measure the impact of wood burning on the levels of air pollutants, nor the impact of related home indoor pollutants on the health of its inhabitants. However, this survey found the prevalence of residential wood heating to be 18.5% in Quebec (11.9%, every day), which is very close to the approximately 20% documented by the 2003 Canadian Survey of Household Energy Use [28]. As well, heating with wood during the winter was not influenced by smog warnings. From a public health standpoint, these results are of concern for several reasons.

First, wood smoke associated with residential wood burning has known negative impacts on health. It is likely to cause a variety of adverse respiratory health effects, including increases in respiratory symptoms, lung function deterioration, and increased visits to emergency departments and hospitalizations [29]. Furthermore, wood smoke is an important contributor to particle concentrations [29] and its increased use could result in a substantial increase in the number of premature deaths [30]. Clearly, there seems to be no reason to assume that the effects of particulate matter in areas polluted by wood smoke are weaker than elsewhere [31].

Second, in 2003, 30% of the atmospheric emissions generated by the total of fixed sources in Québec were attributable to wood heating and are increasing [32]. It is likely that residential biomass combustion will become even more widespread, given the recent upward trend in the costs of oil and natural gas [29]. Moreover, the use of wood as a primary or secondary source of heat is presently encouraged by the Canadian government as a useful adaptation in defense against the harmful effects of prolonged power outages brought on by extreme climatic events[9]. Furthermore, a close and continuous monitoring of the evolution in residential wood heating does not exist at the present time.

Third, even in densely populated urban environments where most people live in apartments and where the prevalence of wood heating is very low (e.g. Montréal in this survey), air quality can be severely affected by wood smoke. For example, air quality measures implemented between 1999 and 2002 in Montréal have demonstrated that some atmospheric pollutants (e.g. particulate matter) in a residential district using wood heating to a great extent were up to five times higher in winter than in summer, and up to two times higher in winter in that district than in downtown high traffic areas [33].

Fourthly, this survey found that the use of residential wood heating does not seem to be influenced either by the perception of living in a region conducive to smog, or by the smog warnings emitted by Environment Canada through the media. This may be due to the fact that the Info-Smog program did not cover the regions with the highest prevalence of wood heating during this study. This program informs the population through the media about the presence of meteorological conditions conducive to increased atmospheric pollution, and sends, at the same time, advice about reducing the sources of pollution and their health impacts [34]. This is a possible but refutable hypothesis: the perception and warnings about smog do not seem to affect the use of an automobile or a remote starter (two other sources of smog) in Montréal [17], where Info-Smog has existed since its creation in 1994 [34]. However, many other determinants – besides the perception of risk and the knowledge relating to it – can promote the adoption of a health-related behaviour, and these are mainly habit, social determinants (e.g., behaviour standards, pressure felt), beliefs, moral principles [35, 36], and other variables (e.g. type of dwelling, accessibility of wood) in particular in regions characterized by colder and longer winters [37].

Finally, the average age of wood stoves used as the primary heating system in Canada was 12 years in 2003 [38] and it is likely that the stoves used as a secondary source of heat are just as old. Chances are that a significant proportion of these appliances are not certified according to the standards of the United States Environmental Protection Agency (EPA) [39] or not approved by the Canadian Standards Association (environmental performance standard B.415.1-04), if only because the costs of purchasing and installing the new technologies would be between $1,800 and $5,000 per stove [40]. In addition, no Canadian law prohibits the sale of uncertified wood burning appliances, which emit in nine hours as much fine particulate matter into the atmosphere as a certified stove operating for 60 hours, or as an intermediate type automobile traveling 18 000 km in a year [7]. In this survey, the type of appliance and the year of acquisition were not evaluated. However, it would be surprising that these specifications differ greatly from the rest of Canada.

Consequently, in Canada and other similar cold regions (e.g. Northern Europe, Russia), it would be appropriate to implement long-term national programs on residential wood heating to reduce pollutant emissions at source. Such a program could simultaneously include feasible adaptation measures of the "no-regrets" type (which are measures with climatic and non-climatic benefits). Such an approach would include educational measures (e.g. observance of good practice), incentive measures (e.g. financial assistance for replacing a conventional appliance and its recycling), and legislative measures including various control strategies (e.g. prohibition of the sale of uncertified wood burning appliances, prohibition of wood heating on smog days) [40, 41] plus simultaneous mechanisms to ensure their application (e.g., high fines for polluting citizens and municipal administrations). In addition, close and continuous monitoring [42] of the evolution in residential wood heating would be necessary, including variables related to atmospheric and indoor pollutants, appliances, their actual use, installation and maintenance, users, the natural environment (e.g., wind, topographical characteristics) and the dwellings (e.g., ventilation of the dwelling). Finally, research is needed on the cultural and psychosocial determinants of heating practices to help focus intervention programs and on the health impacts of wood heating for highly exposed groups under conditions of a developed country [30], as is the case for Québec.

In recent years, much has been written about heat waves that have occurred in some industrialized countries. While this is important, it would be also desirable to remember that there will still be winters and periods of intense cold in the northern regions, such as Canada, and that people will still have to continue to adapt to them. It is indisputable that wood heating is an interesting adaptation strategy for protection against the cold during extreme climatic events that can lead to prolonged power outages, particularly when this renewable energy resource is easily accessible in several northern countries. However, in the light of the results of this study and the literature on air pollution and climate change, it is important to state that much remains to be done, individually and collectively, to avoid wood heating becoming in fact a maladaptation. In light of the precautionary principle, the current imprecise and incomplete "scientific evidence" associated to the health and environmental impacts of residential wood heating is, in our view, an additional reason to implement a long-term national program on improved and controlled wood heating as part of "no-regrets" adaptation measures to climate change that brings more heating autonomy to dwellings during severe climate events while reducing air pollution and its associated health impacts.