As a national institute for occupational health our aim is to focus on emerging threats such as climate change and how it impacts on workers’ health. Dry (El Nino) and wet (La Nina) weather patterns resulting from climate change continue to impact on the environment and consequently on occupational health.  The effects of heat stress and rising carbon dioxide (CO2) levels may be more obvious examples however it also has an impact on occupational allergies and infectious diseases in several ways.  The three categories or priority areas for the NIOH Immunology & Microbiology Department are: bioaerosols, occupational allergies and water- and vector- borne pathogens.


There is limited information on the health effects of climate change on the concentration of bioaerosols (airborne biological agents).  Changes in temperature, precipitation and wind speed are of critical importance as it determines the horizontal and vertical dilution of bioaerosols.  The special range of bioaerosol transmission can extend from a few meters to several kilometres and is depending on the meteorological conditions above that influence bioaerosol dilution or inactivation.  The main factors that change the risk of diseases associated with extreme weather events are the type and location of occupational activity, duration of exposure, host-specific dose and response effects. Response workers who handle environmental emergencies for example healthcare workers and rescue teams are at greater risk of exposure to the biological hazards associated with sudden, extreme weather events (e.g. moulds, biological agents, microbial by-products and faecal matter during flooding). Water damaged buildings from rain or floods can lead to mould growth causing allergic, infectious and toxic effects.  Severe weather patterns can also affect microbial indoor air quality in buildings. The use of airconditioners for comfortable indoor air environment during hot or warm humid climates can be a source of bacterial and mould exposure as well.  Furthermore, a lack of mechanically ventilated systems due to increasing energy cost (heat, cool, dehumidify) in modern crowded buildings, where natural ventilation cannot adequately dilute the air could lead to increased levels of infectious agents (e.g. Mycobacterium tuberculosis).  Workers in modern buildings without outdoor air ventilation are therefore at increased risk of acquiring TB.

Occupational allergies

The prevalence of allergic diseases is increasing rapidly in the last two decades.  Workers especially those who work outdoors may be exposed to increased levels of various types of allergens.  Increasing temperatures and CO2 levels promote earlier flowering periods, lengthen pollen seasons, increase the quantities of allergens produced, intensify allergenicity, and concentration of pollens and other aeroallergens (moulds spores) and its distribution. Distribution of allergenic insects such as wasps and fire ants has been shown to increase in high temperatures.  The effects of exposure to pollens and other airborne allergens in the workplace could translate into high incidences of occupational respiratory diseases such as asthma and allergic rhinitis. The components of air pollution interact with the allergens transported by pollen grains and could therefore increase the risks of atopic sensitivity and aggravate symptoms in already-sensitized individuals. Workers in industries where jobs are performed outdoors for a long time and require intense physical effort which increase their respiratory flow, have a greater potential of exposure to aeroallergens and can be sensitised (e.g. agriculture).  Due to periods of dry weather conditions in South Africa, products such as wheat and maize are imported from other countries and workers in the milling companies may be exposed to different types of allergens as a result.  The prevalence and severity of respiratory allergies are increasing and remains an occupational health concern.

Depletion of the ozone layer (stratosphere) that shields the earth from the Sun’s UV rays can result in greater levels of sunburn, skin cancer & enhanced phototoxicity and photosensitivity (‘sun allergy’) reactions which are immune system reactions that are triggered by sunlight. These occur in individuals taking certain medications (diuretics, some antibiotics, and oral contraceptives) and using sun screens when working outdoors e.g. farmers, fishermen and workers in construction, road maintenance, landscaping, and horticulture sectors, as well as lifeguards.  Heat stress also impacts on the hydration levels of the skin.  The less hydrated the skin is the more sensitive it is to irritants in the workplace possibly leading to irritant contact dermatitis. The NIOH skin clinic can perform measurements of the trans-epidermal water loss of the skin.  Many outdoor workers may be affected and some in remote and hot parts of the country are particularly vulnerable.

Waterborne and vector borne pathogens

Waterborne diseases are caused by a variety of microorganisms and biotoxins which lead to devastating illnesses such as cholera, schistosomiasis and other gastrointestinal problems.  Outbreaks of waterborne diseases often occur after severe precipitation events (e.g. rainfall, snowfall) which result in elevated waterborne disease burden.  Climate change is likely to increase diarrheal disease incidence worldwide, and extreme weather conditions may also complicate already inadequate prevention efforts. Although South Africa has prevention and treatment strategies for waterborne diseases, the prevalence is fairly low possibly due to underreporting, lack of standardised diagnostic approaches and understanding of the impact of climate change on these diseases.

The prevalence of vector-borne and zoonotic diseases could increase, according to predictions made in connection with climate change. Higher temperatures would change incubation rates, transmission seasons, and geographic distributions of vector insects (ticks and mosquitoes) and disease-carrying animals; and the rise in temperatures would facilitate the development or introduction of new pathogens or disease vectors in livestock. This is likely to the incidence of infectious diseases and the appearance of new vector-borne diseases. Environmental emergency responders, entomologists, and people who perform necropsies on animals, or who handle possibly infected tissues or fluids are also at risk.

Gaps and future research

Through health risk assessments and intervention studies potential occupational health threats can be brought to the attention of policy makers early and help inform policies to reduce the adverse impacts of climate change.
–      Assess current and future risks related to aeroallergens and microbial diseases
–      Assess skin dehydration and photosensitivity in outdoor workers during extreme heat episodes.
–      Evaluate and monitor exposures and health risks of hazardous biological contaminants including allergens likely to be increasingly released due to climate change and its effect on workers health
–      Improve understanding of harmful microbial blooms as well as the biotoxins in water distributions systems and potential health affects to workers
–      Awareness on the impact of reuse of water storage tanks due to drought conditions (leaching of chemicals)

Services we offer

–      Conduct to diagnose new exposures including allergens and conduct indoor air assessments
–      Conduct awareness campaigns to make workers and health professionals aware of the effects on climate on their health
–      Develop measures for raising awareness and informing workplaces (workers and employers) of the potential disease risks associated with climate change


P. R. Morey. Climate change and potential effects of microbial air quality in built environment. Sep 25 2010. US Environmental Protection Agency, Washington, D.C, 20460
Impacts of Climate Change on Occupational Health and Safety Studies and Research Projects REPORT R-775
IRSST [Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST)] April 2013
Climate change and skinBalato NAyala FMegna MBalato APatruno CItal Dermatol Venereol. 2013 Feb;148(1):135-46.
BHM Ngahane, D Noah, YMNjankouo and LR Njock.  2016.  Sensitization to common aeroallergens in a population of young adults in a sub-Saharan Africa setting: a cross-sectional study.  Allergy, Asthma & Clinical Immunology.  12:1. DOI 10.1186/s13223-015-0107-8

Fourie A, Kirsten Z, Matuka O, Ratshikhopha E, Singh T