The 2020 report of The Lancet Countdown on health and climate change: responding to converging crises.

TRANSLATIONS: For the Chinese, French, German, and Spanish translations of the abstract see Supplementary Materials section.

Tracking the impacts of climate change on human health via indicators: lessons from the Lancet Countdown.

BACKGROUND: In the past decades, climate change has been impacting human lives and health via extreme weather and climate events and alterations in labour capacity, food security, and the prevalence and geographical distribution of infectious diseases across the globe. Climate change and health indicators (CCHIs) are workable tools designed to capture the complex set of interdependent interactions through which climate change is affecting human health. Since 2015, a novel sub-set of CCHIs, focusing on climate change impacts, exposures, and vulnerability indicators (CCIEVIs) has been developed, refined, and integrated by Working Group 1 of the "Lancet Countdown: Tracking Progress on Health and Climate Change", an international collaboration across disciplines that include climate, geography, epidemiology, occupation health, and economics. DISCUSSION: This research in practice article is a reflective narrative documenting how we have developed CCIEVIs as a discrete set of quantifiable indicators that are updated annually to provide the most recent picture of climate change's impacts on human health. In our experience, the main challenge was to define globally relevant indicators that also have local relevance and as such can support decision making across multiple spatial scales. We found a hazard, exposure, and vulnerability framework to be effective in this regard. We here describe how we used such a framework to define CCIEVIs based on both data availability and the indicators' relevance to climate change and human health. We also report on how CCIEVIs have been improved and added to, detailing the underlying data and methods, and in doing so provide the defining quality criteria for Lancet Countdown CCIEVIs. CONCLUSIONS: Our experience shows that CCIEVIs can effectively contribute to a world-wide monitoring system that aims to track, communicate, and harness evidence on climate-induced health impacts towards effective intervention strategies. An ongoing challenge is how to improve CCIEVIs so that the description of the linkages between climate change and human health can become more and more comprehensive.

Challenges in conducting epidemiological field studies evaluating associations between heat stress and renal health among workers in informal sectors: experiences from India.

Well-designed Environmental Epidemiological Studies (EES) play a crucial role in quantifying the influence of environmental exposures and their associated risks on health in the wider population. They provide critical research evidence for identifying and developing interventions to avert adverse health consequences from those exposures. However, uncertainty and variability inherent to any field based EES could hinder the nature and magnitude of association between an exposure and health outcome. This is particularly pronounced in resource limited settings and resource-tight research projects. The present study evaluated the association between occupational heat stress and renal health among informal work sectors in India which had some significant challenges. Informal workers exposed to chronic occupational heat stress had significantly higher adverse renal health outcomes than the unexposed workers. Our field challenges included gaining access and permissions to conduct the study, participant recalls bias and attrition, accurately estimating exposures, confounding from causes of both exposure and disease, and to a large extent tight-funding. Though opportunities are abundant, we must ensure field conditions are optimized to attain study objectives. A keen understanding and sensitivity towards the cultural and work settings is essential for successful project completion. Based on our experiences, we provide strategies to adopt to improve fieldwork and provide recommendations to help overcome the field challenges and achieve better results for future EES studies in developing country settings.

Heat Stress Impacts on Cardiac Mortality in Nepali Migrant Workers in Qatar.

BACKGROUND: Qatar is a major destination country for Nepali migrant workers (NMWs; main age range 25-35 years) in the construction trade. These 120,000+ NMWs are exposed to various occupational hazards, including excessive heat, and 3-4 workers die each week. Our study aimed to show whether heat exposure caused deaths. METHODS: The worker population and mortality data of NMWs were retrieved from government institutions in Nepal. Heat exposure was assessed by monthly estimates of daily wet bulb globe temperature (WBGT), for in-shade conditions, from data collected at the Doha weather station from 2009 to 2017. Working in the sun during the middle of the day would add 2-3°C to the in-shade WBGT values. Daily deaths and their causes were obtained from the records of the Foreign Employment Promotion Board (FEPB) in Nepal, 2009-2017. Interviews with returning NMWs about their working conditions and the impacts of these conditions added information. The association between the heat variable and mortality was tested with standard statistical methods. RESULTS: The average annual death rate for NMWs in Qatar was 150 deaths/100,000. According to interviews, the majority of NMWs were found working in high WBGT (>31°C) each working day during hot months. The major cause of these deaths was recorded as cardiovascular problems (cardiovascular disease; CVD). Unfortunately, the causes of death were poorly described, and many deaths were listed as "cardiac arrest." We included these deaths in the broader category of "cardiovascular causes." There was a strong correlation between average monthly afternoon heat levels (WBGT) and CVD mortality. It is likely that a large proportion of these CVD deaths during hot months were due to serious heat stroke. Global studies show that approximately 15% of deaths in the age group 25-35 years are due to CVD causes. However, in this NMW population, the figures were 22% during the cool season and 58% during the hot season. CONCLUSIONS: The increased CVD mortality during hot periods is most likely due to severe heat stress. As many as 200 of the 571 CVD deaths during 2009-2017 could have been prevented if effective heat protection had been implemented as a part of local occupational health and safety programs. There is an urgent need for protection against such heat effects among NMWs, and rising temperatures from ongoing climate change are further increasing the health risks. Cause of death records for workers dying in hot conditions should be more precise than "cardiac arrest."

Workplace heat exposure, health protection, and economic impacts: A case study in Canada.

BACKGROUND: Occupational heat exposure is a serious concern for worker health, productivity, and the economy. Few studies in North America assess how on-site wet bulb globe temperature (WBGT) levels and guidelines are applied in practice. METHODS: We assessed the use of a WBGT sensor for localized summertime heat exposures experienced by outdoor laborers at an industrial worksite in Ontario, Canada during the warm season (May-October) from 2012 to 2018 inclusive. We further examined informed decision making, approximated workers' predicted heat strain (sweat loss, core temperature), and estimated potential financial loss (via hourly wages) due to decreased work allowance in the heat. RESULTS: Significantly higher worksite WBGT levels occured compared with regional levels estimated at the airport, with an upward trend in heat warnings over the 7 years and expansion of warnings into the fall season. The maximum WBGT during warnings related strongly to predicted hourly sweat loss. On average, 22 hours per worker were lost each summer (~1% of annual work hours) as a result of taking breaks or stopping due to heat. This amount of time corresponded to an average individual loss of C$1100 Canadian dollars (~C$220,000 combined for ~200 workers) to workers or the company. The additional losses for an enterprise due to reduced product output were not estimated. CONCLUSIONS: Worksite observations and actions at the microscale are essential for improving the estimates of health and economic costs of extreme heat to enterprises and society. Providing worksite heat metrics to the employees aids in appropriate decision making and health protection.

Surveillance of work environment and heat stress assessment using meteorological data.

Health surveillance and workplace surveillance are two related but different aspects of occupational health services. The assessment of heat stress using heat indices and thermal models in connection with meteorological data is an important part of surveillance of workplace heat. The assessment of heat exposure provides the basis for occupational health services. Workers should have health surveillance if the high heat stress cannot be reduced.

Is ambient heat exposure levels associated with miscarriage or stillbirths in hot regions? A cross-sectional study using survey data from the Ghana Maternal Health Survey 2007.

It is well established that high ambient heat could cause congenital abnormalities resulting in miscarriage or stillbirth among certain species of mammals. However, this has not been systematically studied in real field settings among humans, despite the potential value of such knowledge for estimating the impact of global warming on the human species. This study sought to test the hypothesis that maternal heat exposure during pregnancy in hot regions is associated with increased prevalence of spontaneous abortions or stillbirths and to develop an analytical strategy to use existing data from maternal health surveys and existing data on historical heat levels at a geographic grid cell level. A subsample of the Ghana Maternal Health Survey 2007 was used in this study. This study sample consisted of 1136 women with pregnancy experiences between 2004 and 2007, out of which 141 women had a pregnancy that terminated in miscarriage or stillbirth. Induced-abortion cases were excluded. The linkage between ambient heat exposure and pregnancy outcome followed the epidemiological time-place-person principle, by linking timing of pregnancy outcome with historical data of local area heat levels for each month, as estimated in an international database. Maternal heat exposure level was estimated using calculated levels of the wet-bulb globe temperature (WBGT), which takes into account temperature, humidity, heat radiation, and air movement over the skin (wind speed). The values we used applied to exposure in the shade or in buildings without cooling (no solar heat radiation) and a standard air movement of 1 m/s. We applied two exposure durations: yearly average and monthly average for second month of pregnancy. In one analysis, we restricted the sample to four regions with time-homogeneous ambient heat. Analysis was made using logistic regression. About 12% of the latest pregnancies ended in either miscarriage (9.6%) or stillbirth (2.8%). The odds ratios indicated 12 to 15% increase (ORcrude 1.15, 95% CI 0.92-1.42, and ORage adjusted 1.12, 95% CI 0.90-1.39) in the odds of having a stillbirth or miscarriage with each additional degree increase in WBGT, although this was just outside two-sided statistical significance. The WBGT range was quite narrow (most annual values in the range 24-26 °C, and most monthly values in the range 23-27 °C), which may have hidden any real impacts of high heat levels. The seemingly positive association observed disappeared after adjusting for gravidity. The analyses of the four selected regions indicated 27 to 42% increase in the odds of experiencing miscarriage or stillbirth with every degree increase in WBGT (crude OR 1.42 95% CI 1.00-2.03). This association remained after adjusting for maternal age pregnancy history, although no longer statistically significant (adjusted OR 1.27, 95% CI 0.89-1.81). Environmental heat exposures may be associated with adverse pregnancy outcomes, but this study was inconclusive, possibly because the heat exposure range was small. Historical records of routine observations in existing databases can be used for epidemiological studies on the health effects of heat, although data from properly and purposively designed studies might be more suitable for further studies.

Occupational heat stress assessment and protective strategies in the context of climate change.

Global warming will unquestionably increase the impact of heat on individuals who work in already hot workplaces in hot climate areas. The increasing prevalence of this environmental health risk requires the improvement of assessment methods linked to meteorological data. Such new methods will help to reveal the size of the problem and design appropriate interventions at individual, workplace and societal level. The evaluation of occupational heat stress requires measurement of four thermal climate factors (air temperature, humidity, air velocity and heat radiation); available weather station data may serve this purpose. However, the use of meteorological data for occupational heat stress assessment is limited because weather stations do not traditionally and directly measure some important climate factors, e.g. solar radiation. In addition, local workplace environmental conditions such as local heat sources, metabolic heat production within the human body, and clothing properties, all affect the exchange of heat between the body and the environment. A robust occupational heat stress index should properly address all these factors. This article reviews and highlights a number of selected heat stress indices, indicating their advantages and disadvantages in relation to meteorological data, local workplace environments, body heat production and the use of protective clothing. These heat stress and heat strain indices include Wet Bulb Globe Temperature, Discomfort Index, Predicted Heat Strain index, and Universal Thermal Climate Index. In some cases, individuals may be monitored for heat strain through physiological measurements and medical supervision prior to and during exposure. Relevant protective and preventive strategies for alleviating heat strain are also reviewed and proposed.

Estimated work ability in warm outdoor environments depends on the chosen heat stress assessment metric.

With a view to occupational effects of climate change, we performed a simulation study on the influence of different heat stress assessment metrics on estimated workability (WA) of labour in warm outdoor environments. Whole-day shifts with varying workloads were simulated using as input meteorological records for the hottest month from four cities with prevailing hot (Dallas, New Delhi) or warm-humid conditions (Managua, Osaka), respectively. In addition, we considered the effects of adaptive strategies like shielding against solar radiation and different work-rest schedules assuming an acclimated person wearing light work clothes (0.6 clo). We assessed WA according to Wet Bulb Globe Temperature (WBGT) by means of an empirical relation of worker performance from field studies (Hothaps), and as allowed work hours using safety threshold limits proposed by the corresponding standards. Using the physiological models Predicted Heat Strain (PHS) and Universal Thermal Climate Index (UTCI)-Fiala, we calculated WA as the percentage of working hours with body core temperature and cumulated sweat loss below standard limits (38 °C and 7.5% of body weight, respectively) recommended by ISO 7933 and below conservative (38 °C; 3%) and liberal (38.2 °C; 7.5%) limits in comparison. ANOVA results showed that the different metrics, workload, time of day and climate type determined the largest part of WA variance. WBGT-based metrics were highly correlated and indicated slightly more constrained WA for moderate workload, but were less restrictive with high workload and for afternoon work hours compared to PHS and UTCI-Fiala. Though PHS showed unrealistic dynamic responses to rest from work compared to UTCI-Fiala, differences in WA assessed by the physiological models largely depended on the applied limit criteria. In conclusion, our study showed that the choice of the heat stress assessment metric impacts notably on the estimated WA. Whereas PHS and UTCI-Fiala can account for cumulative physiological strain imposed by extended work hours when working heavily under high heat stress, the current WBGT standards do not include this. Advanced thermophysiological models might help developing alternatives, where not only modelling details but also the choice of physiological limit criteria will require attention. There is also an urgent need for suitable empirical data relating workplace heat exposure to workability.

Estimating population heat exposure and impacts on working people in conjunction with climate change.

Increased environmental heat levels as a result of climate change present a major challenge to the health, wellbeing and sustainability of human communities in already hot parts of this planet. This challenge has many facets from direct clinical health effects of daily heat exposure to indirect effects related to poor air quality, poor access to safe drinking water, poor access to nutritious and safe food and inadequate protection from disease vectors and environmental toxic chemicals. The increasing environmental heat is a threat to environmental sustainability. In addition, social conditions can be undermined by the negative effects of increased heat on daily work and life activities and on local cultural practices. The methodology we describe can be used to produce quantitative estimates of the impacts of climate change on work activities in countries and local communities. We show in maps the increasing heat exposures in the shade expressed as the occupational heat stress index Wet Bulb Globe Temperature. Some tropical and sub-tropical areas already experience serious heat stress, and the continuing heating will substantially reduce work capacity and labour productivity in widening parts of the world. Southern parts of Europe and the USA will also be affected. Even the lowest target for climate change (average global temperature change = 1.5 °C at representative concentration pathway (RCP2.6) will increase the loss of daylight work hour output due to heat in many tropical areas from less than 2% now up to more than 6% at the end of the century. A global temperature change of 2.7 °C (at RCP6.0) will double this annual heat impact on work in such areas. Calculations of this type of heat impact at country level show that in the USA, the loss of work capacity in moderate level work in the shade will increase from 0.17% now to more than 1.3% at the end of the century based on the 2.7 °C temperature change. The impact is naturally mainly occurring in the southern hotter areas. In China, the heat impact will increase from 0.3 to 2%, and in India, from 2 to 8%. Especially affected countries, such as Cambodia, may have losses going beyond 10%, while countries with most of the population at high cooler altitude, such as Ethiopia, may experience much lower losses.

Impact of climate change on occupational health and productivity: a systematic literature review focusing on workplace heat.

BACKGROUND: With climate change, mean annual air temperatures are getting hotter and extreme weather events will become more and more common in most parts of the world. OBJECTIVES: As part of the EU funded project HEAT-SHIELD we conducted a systematic review to summarize the epidemiological evidence of the effects of global warming-related heat exposure on workers' health and productivity. METHODS: Three separate searches, focused, respectively, on: i) heat-related illness (HRI), cardiovascular, respiratory and kidney diseases; ii) traumatic injuries; and iii) vector-borne diseases or vectors distribution, were conducted in PubMed. EMBASE was also consulted to retrieve relevant studies focused on the health effects of climate change. A fourth search strategy to assess the effects on work productivity was conducted both in PubMed and in the SCOPUS database. RESULTS: A significant proportion of studies reported findings regarding the Mesoamerican nephropathy issue. This is a disease occurring especially among young and middle-aged male sugarcane workers, without conventional risk factors for chronic kidney disease. For injuries, there is a reversed U-shaped exposure-response relationship between Tmax and overall daily injury claims. Outdoor workers are at increased risk of vector-borne infectious diseases, as a positive correlation between higher air temperatures and current or future expansion of the habitat of vectors is being observed. As for productivity, agriculture and construction are the most studied sectors; a day with temperatures exceeding 32°C can reduce daily labour supply in exposed sectors by up to 14%. CONCLUSIONS: The present findings should inform development of further research and related health policies in the EU and beyond with regard to protecting working people from the effects of workplace heat during climate change.

Heat, Human Performance, and Occupational Health: A Key Issue for the Assessment of Global Climate Change Impacts.

Ambient heat exposure is a well-known health hazard, which reduces human performance and work capacity at heat levels already common in tropical and subtropical areas. Various health problems have been reported. Increasing heat exposure during the hottest seasons of each year is a key feature of global climate change. Heat exhaustion and reduced human performance are often overlooked in climate change health impact analysis. Later this century, many among the four billion people who live in hot areas worldwide will experience significantly reduced work capacity owing to climate change. In some areas, 30-40% of annual daylight hours will become too hot for work to be carried out. The social and economic impacts will be considerable, with global gross domestic product (GDP) losses greater than 20% by 2100. The analysis to date is piecemeal. More analysis of climate change-related occupational health impact assessments is greatly needed.

The Effects of Climate Change on Cardiac Health.

The earth's climate is changing and increasing ambient heat levels are emerging in large areas of the world. An important cause of this change is the anthropogenic emission of greenhouse gases. Climate changes have a variety of negative effects on health, including cardiac health. People with pre-existing medical conditions such as cardiovascular disease (including heart failure), people carrying out physically demanding work and the elderly are particularly vulnerable. This review evaluates the evidence base for the cardiac health consequences of climate conditions, with particular reference to increasing heat exposure, and it also explores the potential further implications.

Heat-related symptoms in sugarcane harvesters.

BACKGROUND: Exposure to heat stress is a documented risk for Central American sugarcane harvesters. However, little is known about heat-related illness in this population. METHODS: This study examined the frequency of heat-related health effects among harvesters (n = 106) exposed to occupational heat stress compared to non-harvesters (n = 63). Chi-square test and gamma statistic were used to evaluate differences in self-reported symptoms and trends over heat exposure categories. RESULTS: Heat and dehydration symptoms (headache, tachycardia, muscle cramps, fever, nausea, difficulty breathing, dizziness, swelling of hands/feet, and dysuria) were experienced at least once per week significantly more frequently among harvesters. Percentages of workers reporting heat and dehydration symptoms increased in accordance with increasing heat exposure categories. CONCLUSIONS: A large percentage of harvesters are experiencing heat illness throughout the harvest demonstrating an urgent need for improved workplace practices, particularly in light of climate change and the epidemic of chronic kidney disease prevalent in this population.

Working in Australia's heat: health promotion concerns for health and productivity.

This exploratory study describes the experiences arising from exposure to extreme summer heat, and the related health protection and promotion issues for working people in Australia. Twenty key informants representing different industry types and occupational groups or activities in Australia provided semi-structured interviews concerning: (i) perceptions of workplace heat exposure in the industry they represented, (ii) reported impacts on health and productivity, as well as (iii) actions taken to reduce exposure or effects of environmental heat exposure. All interviewees reported that excessive heat exposure presents a significant challenge for their industry or activity. People working in physically demanding jobs in temperatures>35°C frequently develop symptoms, and working beyond heat tolerance is common. To avoid potentially dangerous health impacts they must either slow down or change their work habits. Such health-preserving actions result in lost work capacity. Approximately one-third of baseline work productivity can be lost in physically demanding jobs when working at 40°C. Employers and workers consider that heat exposure is a 'natural hazard' in Australia that cannot easily be avoided and so must be accommodated or managed. Among participants in this study, the locus of responsibility for coping with heat lay with the individual, rather than the employer. Heat exposure during Australian summers commonly results in adverse health effects and productivity losses, although quantification studies are lacking. Lack of understanding of the hazardous nature of heat exposure exacerbates the serious risk of heat stress, as entrenched attitudinal barriers hamper amelioration or effective management of this increasing occupational health threat. Educational programmes and workplace heat guidelines are required. Without intervention, climate change in hot countries, such as Australia, can be expected to further exacerbate heat-related burden of disease and loss of productivity in many jobs. In light of projected continued global warming, and associated increase in heat waves, more attention needs to be given to environmental heat as a human health hazard in the Occupational Health and Safety arena. Without adoption of effective heat protective strategies economic output and fitness levels will diminish. Health protection and promotion activities should include strategies to reduce heat exposure, limit exposure duration, ensure access to hydration, and promote acclimatization and fitness programmes, and reorientate attitudes towards working in the heat.