1. Introduction
It has been widely documented that exposure of construction workers to excessive heat stress has a paramount impact on their health and well-being as well as their productivity [
1,
2]. This exposure to heat stress has further been exacerbated by the increased frequency of heat waves due to global climate change [
3,
4]. The exposure of construction workers to heat stress is seen as a growing challenge to the construction industry [
5]. Despite the implementation of various strategies and policies within the sector, an increase in heat stress related morbidity and mortality is widely reported [
6]. Heat stress is the largest cause of weather-related deaths in the United States [
7]. Analysis of mortality due to heat stress during 2000–2010 revealed construction workers are extremely vulnerable to heat stress with the second highest risk rate among all industries in the United States [
7]. Workers belonging to small companies (with fewer than 10 employees) had the highest fatality rate, prompting the authors to suggest targeted heat stress prevention interventions in small firms. Small companies are less likely to implement heat stress prevention procedures or monitoring guidelines due to capacity constraints compared to their larger counterparts [
8].
The assessment of the impact of heat waves on construction workers is a growing challenge for the South Australian Construction industry, with adverse impacts on project delivery. It is projected that by 2070 heat waves will triple in South Australia [
1]. Construction workers, working on office environments or sites, will face various challenges in finding the right balance between their required duties and personal safety [
2]. The influence of heat stress on unintentional accidents and injuries is an increasingly important research question in the face of global warming and climate change [
9]. The combination of heat and humidity can put workers’ health at risk, especially during prolonged period of exposure. Evaporative sweat (heat loss) is seen as the mechanism to reduce heat stress and other risks of injury [
4]. Evaporative heat loss through sweat can be restricted by age, gender, low air movement, and protective equipment [
2,
4]. In such cases, a positive body heat and related skin temperatures will increase, leading to heat illness and death in some circumstances. Due to the physical nature of construction work, especially outdoors and on sites, construction workers face a greater risk due to high metabolic rate causing increases in body temperature [
10]. The combined metabolic and environmental heat loads challenge the bodies’ cooling mechanisms in these workers [
7]. For example, roofers perceived an extra 10 °C temperature while working on roofs directly exposed to sunshine [
11]. With the threat of heat wave events, the situation is much worse, even if the level of activity is low; it represents a high risk of heat stress, ill-health, and mortality. It was established that a core body temperature above 40 °C will lead to heat exhaustion. In return, heat exhaustion poses a great threat to life and can lead to complete failure of central nervous thermoregulatory system [
12]. Simmons et al. (2008) argued that minimum increases in body temperature can be detrimental to workers’ performance, cognitively as well as physically [
12]. Increased sweating and high level of heat sensation can cause discomfort and distress, causing distraction and other behavioural changes which can result in accidents and injuries. High levels of sweat during heat waves may result in dehydration. Lieberman (2007) suggested that a 2% or more loss of body weight due to dehydration will result in significant reductions in visual-motor tracking, loss of short term memory, and attention [
13]. It is evident that heat stress can have progressive effects on workers’ health ranging from heat rash, heat cramp, heat fainting, heat exhaustion to heatstroke, leading to morbidity and mortality [
2].
Causes of construction accidents have been extensively studied with a number of theories explaining the root causes [
14]. Uncovering root causes of accidents is very important for the construction industry as it is mainly project-based and transitionary in character, where Work, Health and Safety (WHS) measures are very hard to implement [
15]. Site conditions, type of work, and work environment are considered to be influential in accident causation [
16,
17,
18]. Heat stress can induce other construction accidents through physical fatigue, impaired mental capacity, and misuse of inconvenient personal protective equipment (PPE) [
19]. Using a systems approach, Rowlinson and Jia (2015) studied the causation of heat illnesses in Hong Kong [
20]. Heat illness is considered to be a special case where the victim is often the agent of its cause and prevention largely rests with the victim as well as the institutions surrounding the construction process [
20]. The masculine culture of the construction industry was found to be the major cause of heat stress illnesses, where workers often tend to underestimate the risk while overestimating their capacity to cope with it [
21]. In addition to factors causing construction accidents, factors that influence its severity are also important in order to plan preventive measures. Using worker characteristics, type of work, and the work environment, Dumrak et al. (2013) found that age, experience, gender, and language used by the worker; organization size, project size, and project location; mechanism of accident; and body location of the injury are factors that influence the severity of an accident [
22].
Due to global warming, a large number of countries are at risk of experiencing intense and frequent heat waves. These countries have to assess the human health vulnerability to climate change in order to plan and implement mitigation measures to avoid large calamities. Therefore, more empirical evidence is needed to understand the impact of heat waves on occupational accidents, especially for industries such as construction. This paper aims to investigate the impacts of heat waves on construction accidents using a large number of compensation claims compiled by SafeWork South Australia. These data provide an insight into many variables related with an accident as reported by the victim. The study focuses mainly on the occurrence and severity of accidents during the 2002–2013 period in South Australia. In practical terms, uncovering potential impacts of heat waves on accidents and the groups and activities that are vulnerable could help improve the effectiveness of WHS measures implemented on sites. It will also enhance the construction organizations’ understanding of the potential impacts, thereby allowing them to be able to implement policies on heat stress management more stringently. Additionally, an increased understanding would enable organizations to channel their energies across the groups and activities having the highest vulnerability. As a result, the implementation of WHS measures would be more likely to be successful.
4. Discussion
This study looked at the differences of injuries suffered by construction workers during heat wave and control periods to identify groups and activities that are vulnerable to heat waves. It highlights some important implications for the construction community and WHS authorities. The number of accidents reported during heat wave periods is less compared to control periods, suggesting some control measures are in operation in construction sites to prevent accidents during heat waves. This observation is made by Xiang et al. [
1] as well when they compared accidents during heat waves in several industries. A threshold temperature of 37.7 °C was estimated for construction where the changes to accident rate occurs [
1]. The studies of [
33,
34] also observed less accidents during heat waves compared to normal work days in summer months. The reduction of accidents could be attributed to behavioural changes of workers and preventive measures implemented by the company [
9]. Workers automatically adjust their work pace to reduce excessive strain [
19]. Though self-regulation is an effective method to manage heat stress, purported productivity losses prevent that from happening in construction sites where sub-contracting is a norm rather than exception and payment for work is based on the progress achieved [
19,
35]. In addition, organizational culture plays a role in shaping the workers’ response to heat stress [
20]. For example, a very high power distance and risk taking attitude prevalent in some Asian countries prevent workers from challenging the status quo of the work process and inhibit self-regulation [
20]. Workers tend to “accept the work pressure at the expense of safe working procedures” ([
20], p. 188). The masculine culture of the construction industry displays an underestimation of heat stress risks and overestimation of one’s ability to cope with it [
21]. Therefore, preventive interventions become essential to avoid workers being exposed to excessive heat stress during heat waves. These preventive measures are mainly guided by safety regulations, code of practices, and union work agreements.
Australian health and safety regulations and code of practice recognizes the impact of heat stress on health and safety of workers. SafeWork Australia (2011), recommends an ambient temperate of 20–26 °C to provide optimum thermal comfort for workers depending on the time of the year and clothing worn [
36]. It also notes that workers involved in manual work usually prefer a lower temperature range. According to the code, thermal comfort is affected by many factors, including air temperature, air movement, humidity, clothing, the amount of physical exertion, average temperature of the surroundings, and sun penetration ([
36], p. 14). As heat waves are very frequent and increasing in South Australia, construction workers through the Master Builders Association Combined Unions Compliance Agreement have resorted to a common work procedure to mitigate excessive heat stress at the onset and during heat waves. According to this agreement work areas in a site is divided into the three following categories:
Exposed areas such as exposed work platforms, outdoor work etc. which are directly affected by ambient heat.
Less exposed areas—areas cooler than the general outside temperature (e.g., lower levels of multi-storey buildings, inside or shaded areas, basements, etc.).
Air conditioned areas.
During the onset of a heat wave where the temperature is raising but less than 35 °C, actions need to be taken to minimize heat discomfort and stress of workers in exposed areas. In addition, these workers need to be progressively transferred to appropriate work in less exposed areas. Work in the other two areas will continue normally. When the outside temperate reaches 35 °C, work in exposed areas should cease except where needed to complete concrete pours or emergency work. Workers are entitled to double time rates during these operations. Work in less exposed areas will continue normally but workers can stop work one hour early. However, work in air conditioned areas will continue normally. When the temperature reaches 37 °C, all work in less exposed areas also should cease. The work in air conditioned areas will continue normally. In addition to these agreed work procedures, SafeWork Australia (2011) promotes some best practices to reduce heat strain and heat exhaustion, such as ([
36], p. 14). These measures could be categorized broadly into the following three suggestions: improved ambient conditions using mechanical means (e.g., fans, coolers); isolation of workers from the heat source (e.g., altering work schedule, rest breaks, job rotation, slowing down); and encourage light clothing.
This study captures some of the most vulnerable groups and work activities that need additional attention by WHS authorities and construction companies. Workers in the civil engineering sub-sector were found to be highly vulnerable to accidents in comparison to their building, building services, and general construction counterparts. Their exposure to accidents is approximately 2.4 times higher during heat waves compared to control periods. According to Lundgren et al. (2013), workers in outdoor occupations are the most vulnerable to heat waves [
25]. Workers in civil construction sites do not have the luxury of shade and protection of the structure itself once it is partly completed, like the basement and lower levels of a multi-storey building [
19]. Road construction workers are more vulnerable to radiant heat determined by the open site characteristics [
19]. The personal protective equipment (PPE) worn by these workers also severely impedes heat exchange through evaporation [
25]. Measurements undertaken in Hong Kong revealed 57 °C of air temperature inside a workers’ helmet when the environmental temperature was only 33 °C [
19]. Workers are tempted to take off PPE due to severe heat stress exposing themselves for accidents and injury [
19,
25]. The study highlights the vulnerability of older workers to heat waves with relatively higher occurrence and severity among this cohort. The mean expenditure for injuries was more than double during the heat wave period. Xiang et al. (2013) reported similar observations for the age group of 55 and above [
1]. Similarly, workers from smaller companies are more vulnerable to accidents during heat waves compared to their larger counterparts. It is likely that smaller companies may be less effective in managing WHS as well as complying with the standard heat wave work procedures discussed above. Therefore, implementation of adequate preventive measures in small-sized companies could be a priority of WHS authorities.
While generic guidelines and work procedures are in place to mitigate heat stress in Australia, a lack of targeted interventions specifically tailored to the abovementioned vulnerable groups and work activities is a concern. One of the implications of this research is to highlight the need for such well-focused interventions in order to protect the most vulnerable. For example, as civil construction sites are often dispersed on a large geographical area unlike building sites, some of the general preventive measures might not be suitable to mitigate exposure of workers to excessive heat. Climate change and increases in extreme weather conditions will push the governments and builders alike to find innovative ways of protecting workers from accidents and severe injuries. Further research is needed to unearth the mechanisms through which heat stress can affect workers’ exposure to accidents and ways and means of reducing such exposure. The study showed no statistically significant difference between worksites in Adelaide CBD and its suburbs during heat waves, refuting the hypothesis that heat island phenomena could exacerbate heat stress in high-density urban construction sites. Built-up areas typically absorb and emit a higher volume of long wave radiation in addition to their capacity to store heat for an extended period of time. Therefore, the ambient temperature of these built-up areas is relatively higher than the suburbs and the regional farmland [
25]. Given that Adelaide represents a typical case study of a dense CBD surrounded by parklands that separates the CBD from its suburbs, one could expect the number and severity of injuries during heatwaves to be significantly higher in CBD-based worksites. However, the study could not discriminate the vulnerability of workers based on worksite location.
The findings conclude that three aspects require meticulous scrutiny and constant monitoring to reduce severe accidents on construction sites during heat waves, including: heat stress management in civil engineering sites, small-sized projects and safety implementations, and older workers and the type of work they undertake. Controlling the level of injury severity during heat waves can benefit workers by reducing their sufferings and can benefit builders by sustaining their reputation and turnover in projects. In this regard, the findings can help Safe Work South Australia, who is the owner of the accident database used in the study, in directing/redirecting its focus for accident minimization in the construction industry. The findings can also inform OHS policies and management systems of construction companies. Although, the study was conducted in the context of South Australia, the findings can be generalized and applied to the construction sector in other parts of Australia or even overseas that possess similar environmental characteristics.
While the study makes several contributions to the practice of heat stress management in construction projects, some limitations should be noted. The major limitation point is in regards to the use of a claims database to obtain injury data during heat waves and control periods [
37,
38]. Such data would not allow rigorous in-depth analyses compared to other tools such as case studies [
24,
39,
40,
41], questionnaire surveys [
42,
43,
44,
45], or interviews [
40]. Second, all variables associated with an accident cannot be included in the analysis due to the limited number of variables reported in a database. Third, all accidents occurring during the period under consideration would not be reported, especially the minor accidents which do not benefit from claims or fatalities for which no next-of-kin are available to report. In addition, with regard to the use of claim databases, people working in the informal sector and as sole traders or partnerships would not have insurance policies, and those accidents would be totally missed from reporting [
37]. Thus, underreporting can create a bias in the sample that is being analysed [
38,
46]. However, claims databases are much superior compared to government databases, as the latter does not have a reward or incentive inbuilt for reporting [
38]. Despite these limitations, the major advantage of using claims databases is the large sample size. The present study uses 29,438 compensation claims and the large sample size provides an opportunity to use statistical tools to generalize the results.