A growing number of epidemiological studies worldwide have suggested that construction workers are disproportionately at higher risk of heat-related morbidity and mortality [20, 21]. The positive temperature-illness/injury association raises the concerns over the increasing occupational health and safety challenge for construction workers in a warming climate [3, 10]. A better understanding of how construction workers perceive the hazards of workplace heat exposure is warranted for the development of evidence-based heat prevention strategies to minimize the impact of extremely high temperature on workers’ health and safety . However, to our best knowledge, only a few studies have investigated the heat risk perceptions among Chinese construction workers.
Heat risk perception
Our results showed that very few respondents were concerned about heat exposure in the workplace and less than half of the construction workers were worried about heat-related injuries. Evidence has shown that outdoor workers’ awareness of occupational heat stress varied by countries/regions and industries, affected by factors such as education level, culture/religion, vulnerabilities, acclimatization, adaptive capacity, and local occupational safety management system . Usually, workers in developing countries had relatively lower levels of climate change awareness and heat risk than workers in developed countries , despite a few exceptions such as in Ghana . Compared with a similar study from Australia , the degree of concern about heat exposure among Australian outdoor workers was almost twice that of the construction workers in this study. The relatively low awareness of workplace heat exposure in this study may reflect the cultural and demographic differences between the two countries . Another possible explanation is that outdoor workplaces of South Australia where the maximum temperatures could reach as high as 46.1 °C were indeed hotter than that in China. The increase of average maximum temperature in South Australia was the highest in Australia since 1950, and not surprisingly the public had a strong awareness of climate change related heat impacts .
Our age-specific analysis found that older workers were less concerned about heat exposure than younger workers. This may be because young workers were more likely to undertake dangerous or/and physically demanding tasks in the workplace [37, 38]. In addition, compared with middle-aged and older workers, young workers’ work efficiency was relatively less affected by extremely high temperature. This may be because older workers were less physically tolerant of heat exposure  and therefore more vulnerable to heat-related illnesses/injuries in certain outdoor industries during heatwaves . The paradoxical phenomenon that working efficiency of older workers was more likely to be compromised by heat but less concerned about heat exposure needs further research. One possible explanation is that older workers usually had more power/authority than their younger counterparts in the workplace . Evidence from the Australian workplace has also found that older workers were more likely to suffer high temperature related diseases/injuries during heatwaves compared to young workers . It highlights the need to give priority to improve heat-related health and safety awareness of older construction workers.
Regarding the increased risk of injury/accident during heat, the construction industry did not recognize it until quite recently [3, 25]. “Falling, tripping and slipping” was the most common mechanism of heat-related injury and “excessive sweating, dizziness and yellow-colored urine” were the most common heat-related symptoms reported by the workers in this study, which were similar to previous international literature [23, 40, 41]. We found less than half of the construction workers were concerned about heat-related injury and the identified factors affecting workers’ heat risk awareness include physically demanding job, working close to heat sources, and the experience of heat-related illness/injury. This aligns with previous evidence that workers’ heat risk awareness depends on the severity and magnitude of heat exposure level and their experiences of illnesses/injuries due to heat . In this regard, it is important that heat control practices resonate with workers’ own experience against heat. The respondents’ positive attitudes towards the development of heat policies and regulations indicate an opportunity to strengthen construction workers’ heat risk awareness.
A lack of training can elevate workers’ risk of heat-related illnesses/injuries. Training and education are the most cost-effective way for the control and prevention of heat-related illnesses/injuries . We found the self-reported injury rate among construction workers who have received heat training were less than those without training. Although employers are required to provide regular heat-related trainings (e.g., first aid for heat illness) for workers according to the 2012 AHMP , this study observed that about half of the respondents did not receive heat-related training. Fortunately, a high proportion (89%) of workers were willing to receive more heat-related training. Moreover, we found those who had participated in training showed stronger willingness to support further training than those did not. This may indirectly reflect the effectiveness of previous training and that workers realized the value and benefits of training for their occupational health and safety. Relevant training and education should be focused on workers who did not receive heat-related training before, as our results showed that found they were less willing or resist to accept more training.
The results showed that internet was the main source of heat-related information for construction workers rather than training as observed in a similar study from South Australia conducted in 2012 , indicating that heat stress training in the Chinese workplace was insufficient. Nowadays, internet-based devices and mobile apps are the major way for everyday communication and information access, especially in China with the penetration rate of internet users (about one billion) reaching as high as 70.4% in 2020 . Jacklitsch et al. found that smartphone/tablet applications and online training were the preferred heat stress training delivery methods among oil spill cleanup workers in 2018 in the USA, although printed materials were also desired as they are easy to distribute during training and can serve as a reminder . The widespread internet access and the supportive attitudes towards training among construction workers facilitate the implementation of training. However, the added cost and personnel requirement to employers especially for many small business owners may be a hurdle for the provision of heat training.
Identification of heat stress training needs is important for the delivery of targeted and effective training practice. Jacklitsch et al. identified more training on acclimatization and its implementation as the heat stress training requirements for oil spill cleanup workers in the USA . Given the training needs may vary by occupations and countries, further research could be carried out among construction workers to provide more specific guidance for heat stress training. In this study, about 44.0% of the respondents only drank water when they were thirsty. Feeling thirsty is one of the late signs of dehydration, indicating at least 1% loss of total body weight in water . This indirectly reflects the necessity to reinforce training about dehydration in the workplace.
Individual behavioral responses to heat
The majority of our respondents (81.6%) said that they were willing to adjust their work habits to adapt to the likely increasing hot weather in the future. This enables the transformation from improved awareness, knowledge, and training to achieving the best heat prevention practices, because a good level of knowledge and heat risk awareness is not necessarily translated into behavioral changes . It needs concerted efforts from all involved stakeholders.
Self-pacing is the automatic adjustment of work rate to adapt to heat stress. It has been regarded as an effective way of reducing the risk of heat-related illness and injury . In 2016, Lao et al. interviewed 32 male outdoor workers on the impact of heat in the Australian workplace and found they had a high level of heat adaptability through personal adaptive behaviors . In this study, 78.3% of the respondents said they worked at their own pace during extremely high temperature – there is scope for improving the utilization rate of self-pacing. Its effectiveness is subject to multiple factors. In addition to workers’ awareness and knowledge of heat stress, addressing concerns about losing wages or financial bonus, peer pressure, pressure for project progress, self-perception of effectiveness, sense of self-responsibility, and employers’ attitudes towards self-pacing are crucial for its implementation in the workplace , as self-pacing at work can reduce labour productivity. Employers are usually profit-oriented and are more concerned about production and performance goals rather than the heat stress suffered by workers, which was the most common reason overshowing or marginalizing heat stress prevention [1, 41]. During hot weather, management and workers should share the responsibility for safe work. Unless the management is aware of the workers’ experience and risks and takes preventive measures, it may not be possible to achieve the goal of safe work during heat. Therefore, workers need to be explicitly empowered and trained to ensure the effectiveness of self-pacing. On the other side, local health department should strengthen the inspection to ensure employers’ compliance.
In this study, about one-third of construction workers responded that protective measures against heat were seldom or sometimes adopted in their workplaces. Although wearing PPE (e.g., reflective vests, safety boots, and gloves) was necessary to protect workers from relevant occupational hazards, workers may choose not to wear during hot weather because PPE is often made of water impermeable materials that block effective heat dissipation and increase workers’ heat strain . During hot environment, workers may take off their helmets from time to time to alleviate heat stress and subsequently expose themselves to other hazards on site. A similar problem exists with eye protection equipment. Therefore, heat stress in construction sites is not an isolated occupational hazard. Rowlinson et al. proposed a systematic strategy to cope with heat stress by putting it into the whole construction safety management system .
Current heat interventions in the workplace
There are an abundance of available evidence-based heat management protocols, standards and guidelines . In most cases, specific jobs and tasks involving heat exposure can be predicted in advance, and the risk of heat stress could be lowered or avoided by following the standardized recommendations. Our results showed that most of the surveyed workplaces did not rely much on advanced control measures against heat (i.e., strategies eliminating/replacing risks, engineering controls). Heat prevention measures adopted in the workplace seem to be simple and common-sense (e.g., keeping hydrated, wearing light-colored breathable clothes, resting in the shade, stopping work). Keeping hydrated is important to prevent heat stroke, however, up to 35.2% of respondents said cool drinking water was not available in their building sites. Unavailability of safe drinking water in the workplace has also been reported in other studies from USA , Australia , Saudi Arabia , and India .
Lack of compliance and effective law enforcement is one of the major reasons leading to the occurrence of heat-related morbidity and mortality continues worldwide , especially in tropical and subtropical developing countries [29, 32]. In this study, 11% of the respondents said that they had experienced heat-related illnesses or injuries during extremely hot days. This is in line with international literature from USA  and India , and the percentage of self-reported heat-related injury experience reached as high as 71% among mining workers in Ghana . Protecting outdoor workers from the risk of heat exposure is a great challenge for many workplaces in China. Although heat-related injuries and illnesses are largely preventable if adequate precautions are taken, compliance is problematic . Probably, that is why up to 91.2% of the respondents supported the introduction of more heat-related laws and regulations and about quarter of the respondents were not satisfied with the current preventive measures.
A variety of factors at multiple levels in the workplace may hinder the implementation of heat prevention measures. First, some workers may ignore early symptoms of heat stress due to the widely used piece rate payment in the construction industry, which would hinder workers from regular resting and drinking water . Evidence has shown that piecework pricing could lead to a higher incidence of heat-related injuries among health and safety representatives . Second, heat regulations were likely to pose few restrictions on non-compliant employers if policies were not properly enforced. Our results showed that only one-third of the respondents chose “stop working” as a heat protection measure in extremely high temperature. By contrast, the mandatory “stop working” rules existed in about half of the oil spill cleanup workers in the USA . According to the 2012 AHMP heat policy , “if the daily maximum temperature exceeds 40°C, outdoor work should be stopped on the day”. It should be noted that the 2012 AHMP was jointly released by Ministry of Emergency Management, National Health Commission, Ministry of Human Resources & Social Security, and All-China Federation of Trade Unions. According to the Clause 21 of the AHMP, if employers did not comply with the heat policies, local (county-level) jurisdictions should take enforceable actions to ensure implementation. The AHMP is an administrative regulation. Until now, few local governments have enacted heat-related laws except for the Guangdong Province and Chongqing Municipality. Therefore, the AHMP is not strictly implemented in practice. Third, there is considerable ambiguity and ‘grey zone’ existing in the contents of the AHMP such as the identification of indoor and outdoor work, rendering relevant inspection difficult.
High temperature subsidy
In this study, although about 69.8% of the respondents did not know about the policies of HTS, 73.9% of the respondents had received HTS. Some workers may have not received HTS because it incurred additional costs to employers. According to the 2012 AHMP , employers who arranged workers to work in high temperature weather above 35 °C must pay workers HTSs which are included in the total salary. When the HTS is linked to wages, the increased cost of HTS may have adverse effects on employers’ willingness against heat stress, such as simply ignoring the regulations or preferring to pay low-cost subsidies rather than reducing afternoon working hours. If an employer failed to pay the HTS, workers had the right to report to the human resources department of local government or request labor dispute arbitration in accordance with the law. But few workers did that because they were afraid of losing their jobs .
The purpose of the enaction of 2012 AHMP is to prevent employers from exposing workers to extreme heat without heat prevention. However, due to the lack of inspection and administrative penalty, payment of HTS has not been strictly implemented. Some eligible outdoor workers may have not received HTS while some government/government-sponsored white-collar employees did, raising an issue of environmental inequality. Therefore, there is a need to optimize current heat-related laws and regulations, ensuring HTS to be paid to those really at risk of heat exposure. In addition, trade unions at different levels should support frontline workers to defend their own rights and interests.
This study has several limitations that should be acknowledged. Firstly, due to the relatively small sample size, the generalization of the results should be cautious. Moreover, our respondents were mainly recruited from the construction industry; therefore, cautious should be exercised if extending the results to other industries. Secondly, most of the respondents were male workers partly due to the high proportion of males in the construction industry. Therefore, the results may not represent the views of female workers. Thirdly, those who had the experience of heat-related illnesses and injuries may be more inclined to participate in the survey which is on a completely voluntary basis. Moreover, a convenient snowball sampling method was employed in this study to recruit participants. This may generate potential selection bias and overestimate construction workers’ concerns over high temperatures. In addition, recall and self-reporting bias inevitably exists for a cross-sectional observation study, although we have taken measures such as piloting the questionnaire and shortening the recall period to minimize its impact.