by Amelia Hamiter
Kjellstrom et al. (2015) study how warming temperatures due to climate change may create an occupational health hazard in tropical and subtropical countries that have a significant workforce employed in jobs in hot environments, such as physical jobs which must be done outdoors or in indoor spaces such as some factories that lack efficient cooling systems. (Air conditioning in urban areas is contested, since on a large urban scale it can increase heating of outdoor air, and because of its electricity demands. Thus indoor workplaces in some regions lack sustainable temperature control systems.) This problem is exacerbated by the high humidity of these countries, which reduces the effectiveness of sweating in cooling the body. To avoid excessive heat stress, workers must not work during the hottest hours of the day, which increase in the hottest days of the year. Many of the countries affected by this are low- to middle-income, and this issue can have an impact on their respective gross domestic products (GDPs). Preventative actions include development of coolant systems where possible as well as occupational health advisories, adjusted work hours, and other changes such as increased access to drinking water and education about symptoms of heat strain and heat stroke in the workplace. However, these strategies are limited, and also hold little hope for cutting economic losses. Global action against climate change is the most effective action to take against this situation.
Little assessment has heretofore been done on the effects of heat exposure raised by climate change on people who work in hot climates and on consequent economic consequences. Once surrounding air temperature rises above 37° C, or 98° F, heat from the air transfers to the body, and the body must be cooled by the evaporation of sweat. In high humidity, however, sweating becomes less effective at reducing body heat. Heat stress thus becomes an especially prevalent problem for workers in the humid and prevalently hot weather seasons of tropical and subtropical countries. Workers in these occupations often cannot work during the hottest times of the day and in the hottest days of the year; they must rest more and work more slowly to cope with heat. Physical acclimatization to heat varies individually and is limited to evaporation of sweat from the skin, which has little effectiveness in high humidity.
To further assess current and future climate change impact on local heat exposures for working people, the global Hothaps program has been developed. To evaluate heat data, this program used WBGT (Wet Bulb Globe Temperature), a common heat exposure index that in one value combines temperature, humidity, wind speed, and heat radiation. Only indoor values were evaluated (with the knowledge that the outdoor values tend to be a few degrees higher). Data from weather stations around the world were used to calculate time trends, which communicate trends in monthly or annual averages and trends in number of days above a specific threshold in a year. The “Hothaps-Soft” software developed by this program uses WBGT as heat stress index for workplace conditions and has been made freely available at the site www.ClimateCHIP.org along with the weather station data. This paper shows these calculated time trends graphed for the month of May in Kuala Lumpur, Malaysia.
Additionally, the heat situation of different parts of the world was mapped using WBGT of different months and years calculated from data from the Climate Research Unit at University of East Anglia, UK, and future model data were also included. The paper also shares a heat map for regions of India that indicates reduction in hours of workable daylight in different weather seasons. The authors note, however, that the climate data used most likely mainly represents less urbanized areas, yet urban areas have higher ambient temperature than rural areas due to the “urban heat island” (UHI) effect due to absorption of heat into concrete, asphalt, and other surfaces common in such areas. Hothaps-Soft can compare climate data and estimated WBGT levels at central city weather stations with data from airports to estimate heating trends in urban areas.
The workplaces in which heat strain is a significant issue are difficult to cool, even if they are located indoors. Installing air conditioning in urban workplaces, for example, is highly contested as a sustainable solution since large-scale air conditioning use actually heats local outdoor air and increases electricity demand, and can create a huge energy demand for large cities.
These calculated losses in hours of work were used to estimate economic losses. The authors’ model of work hour loss due to heat evaluated the proportion of national workforces in jobs of varying levels of physical demand and heat exposure along with population estimates for different geographic regions. Future GDP estimates based on international projections were then multiplied with the calculated cumulated annual work hour losses, presented as percentages of daylight work hours. These losses were calculated for different regions for “baseline” (1960-1989) and for future periods (2030 and 2050), with consideration of potential socioeconomic changes and changes of workforce distribution into different industries. The paper includes several tables that show a selection of heat and economics data for varying countries. Some of the countries shown are specified as belonging to the Climate Vulnerable Forum (CVF), an organization of 20 low- and middle-income countries that consider themselves threaten by a climate change risk that has been caused largely by other entities. Compared in the tables to countries not in this category, it is seen that the CVF countries and other low- and middle-income countries experience more days of serious heat per year, greater heat impact change, and greater economic loss estimates, than the non-CVF and high-income countries. Estimated annual losses reach the multibillion dollar levels for several of these low- and middle-income countries, showing that climate change can significantly hamper these countries if not mitigated.
Kjellstrom, T., Meng, M., 2015. Impact of Climate Conditions on Occupational Health and Related Economic Losses: A New Feature of Global and Urban Health in the Context of Climate Change. Asia-Pac. J. of Public Health 10.1177/1010539514568711.