1.3.4  Environmental risk factors

You have learned in previous Modules that infectious agents play a part in the transmission of disease. Infectious agents are pathogenic (disease-causing) bacteria, viruses, fungi, protozoa and parasites. To cause a disease, they must be introduced into our bodies in sufficient quantities. The environmental conditions and practices that facilitate the carrying of such infectious agents into our bodies are termed environmental risk factors. A good example is drinking water, which can be contaminated by human faecal matter that contains these infectious agents. When this water is consumed, we are likely to get diarrhoeal diseases.

There are other ways that infectious agents can get into our bodies; for example, the air we breathe can be contaminated by droplets that come out of a patient’s lungs when they breathe or cough. TB and pneumonia are droplet-related infections that are transmitted in this way. There are also diseases and conditions that are not caused by pathogenic organisms, but are caused by other environmental risk factors, which may be due to chemicals or physical hazards such as noise. Major environmental risks and examples of the diseases and conditions that are related to these risks are indicated in Table 1.3. Further descriptions of these diseases can be found in the Communicable Diseases and Non-Communicable Diseases, Emergency Care and Mental Health Modules.

Table 1.3  Major environmental risk factors with related diseases and conditions.
Environmental risk factorsRelated diseases and conditions
Contaminated water, lack of latrines, poor hand washing, inappropriate solid waste management, open defecation, vector infestationDiarrhoeal diseases, trachoma, schistosomiasis, ascariasis, trichuriasis, hookworm, typhoid fever, relapsing fever
Indoor air pollutionChronic obstructive pulmonary disease, lower respiratory infections, lung cancer
Outdoor/ambient air pollutionRespiratory infections, cardiovascular diseases, lung cancer
General environmental hazards (climate, mosquitoes, nutrition)Diarrhoeal diseases, malnutrition, malaria and other vector-borne diseases; heat exhaustion
Environmental hazards in workplaces (excess noise, heat, dust, chemicals)Injuries, hearing loss, cancer, asthma, back pain, chronic obstructive pulmonary disease

1.3.3  Environmental intervention models

1.4  Human interaction with the environment