Human-induced climate change poses great and growing risks to the social and biological wellbeing of human populations. The impacts will affect, mostly adversely, future levels and patterns of population health, attempts to reduce the rich-poor health gap, and social and political stability. This ‘human dimension’ of climate change is more far-reaching than has been generally recognized in public and policy discourse. This includes a range of heightened risks (and threats to productivity and livelihoods) in many workplace settings around the world.

It is now beyond reasonable doubt that human actions are and will be causing a change in Earth’s climate. The climate varies naturally, across a range of time-scales, in response to cosmological and geological influences. Today, human actions have superimposed an unusually rapid change in the world’s climate. Average surface temperature has increased by almost 1^oC since mid-twentieth century,¹  and most of that warming has been due to human actions.² As the scale of fossil fuel combustion, land-clearing and agricultural activity increases, and as the capacity of the oceans and land surfaces to continue to take up excess carbon dioxide from the atmosphere lessens, the rate of annual global emissions and the resultant atmospheric concentration of greenhouse gases is rising. The CO₂ in air has increased by 40% above its pre-industrial level.²

These global trends in climate are evident also at local level. From weather station data it is possible to estimate the WBGT (Wet Bulb Globe Temperature) occupational heat stress index. ³  The number of days each year that WBGT exceeds a serious heat stress level of 29 ^oC is increasing in most locations around the world, as shown in the figure below. The annual ups and downs in these numbers depend primarily on variations of afternoon temperatures and humidity levels. Further, global atmospheric driving forces, such as the Pacific-based ENSO variations, may determine the location of brief peaks. However, the three-decade trends are quite dramatic in Bangkok and Delhi: more than 100 additional “super-hot” days in Bangkok over this period, and more than 40 additional days in New Delhi. These are urban locations, so an increase in the “urban heat island effect” is likely to have amplified local atmospheric trends. However, for the local working population these local recordings are what matters for heat exposures in workplaces where air conditioning is not (or cannot be) applied. 

Using the DPSEEA framework developed at WHO in the 1990s to display links between driving forces behind environmental health hazards, human exposures and the resulting health effects, we show the framework for climate change and human health impacts in the figure below.

There is a wide variety of health effects that can be linked back to climate change, and many of these are of concern in occupational health, particularly in relation to poor farmers and manual workers in low- and middle-income tropical countries where ongoing and future climate change may have the greatest impacts. A number of occupational health concerns emerge from the above framework content. ^{4, 5}

Specific health hazard exposure issues for working people

Extreme weather events:  Climate trend analysis has indicated that storms, typhoons and hurricanes are becoming more common and more intense. This will increase health risks for working people in the affected areas, including the occupational health risk of emergency workers and post-emergency reparation workers. Because of population increase and the tendency for increasing numbers of poor people to live and work on marginal land, climate change will affect more and more people in this way.

Occupational heat stress:  The physiological basis for heat impacts on working people is well known, and in many situations the workers “self-pacing” (working more slowly and taking more rest breaks) is the major preventive action taken. There is a balance to be struck between the occupational heat stroke risk and the work productivity loss due to slowed down work output. New evidence from field studies and climate change impact analysis highlight that this occupational health concern is of major importance. 

Chemical and biotic exposures:  Environmental concentrations of some hazards that occur in workplace environments will increase. E.g. chemicals used in industry evaporate more quickly into work environments and create higher health risks. Urban air pollutants and aeroallergens will increase in concentration, and ice-bound POPs (persistent organic pollutants) will be released and create health risks for working people and the general public.

Vector-borne diseases:  Clearly, malaria and dengue fever are major public health problems in hot locations and people working outdoors are at particular risk to be bitten by disease carrying mosquitoes. When afternoon heavy labor is very difficult due to heat, and more work needs to be carried out during dawn and dusk periods, high mosquito biting frequency will create additional risks for workers.

Infectious diseases, nutritional security and other social tensions:  The lack of safe drinking water due to droughts or floods will create additional risks for diarrhoeal diseases, which for working age groups will increase the number of illness days of work. When climate change threatens local agricultural production access to food will be reduced and nutritional deficiencies can develop. Weakened, under-nourished, workers are likely to be more accident prone, and to be less productive. The changing environment, e.g. reduced water access and land flooding due to sea-level rise, will also create community tensions and reductions in the capacity to maintain various economic activities. The severe flooding in Thailand in 2011 is one example of the type of damage, and disruption and risks to certain occupations, that climate change may bring.

Conclusions

-  Several of the expected public health impacts of climate change will also affect working people. Among these occupational health hazards extreme weather events, occupational heat stroke, increased chemical exposures due to higher temperatures and vector-borne diseases are likely to be the main threats.

-  Preventive approaches include a higher profile for occupational health services that put climate change impact research into practical policies and actions. This involves: better programs for excessive heat exposures; design for better thermal environments in future workplaces; and implementation of known methods to prevent infectious and vector-borne diseases among workers. Prevention also requires more support from the occupational health expert community for programs to mitigate global climate change.