Impacts on Human Health

Contamination of drinking water is the primary pathway for pathogens in sewage to spread diseases to and from people. People are also exposed to sewage pathogens through soils, food grown in contaminated soils, seafood harvested from contaminated waters, and bathing and recreating in polluted waters.

Sewage contamination warning sign on a beach. Photo © Brian Auer, Creative Commons

Infectious diseases from sewage range can include bacterial salmonella, parasitic giardia and hookworm, among others. Exposure can also lead to topical ailments, such as rashes. ref

Pathogens and Infectious Disease

Diarrheal diseases, such as rotavirus, cholera, and typhoid, are the dominant health concern related to sewage pollution, causing 1.6 million deaths in 2017. ref These diseases can cause severe dehydration, malnutrition, and stunting in children, impairing their growth and mental development. ref The result can be lifelong health complications and damaging consequences for entire communities. Contact with sewage represents an urgent challenge particularly in developing areas, and has led to the development of the Water, Sanitation, and Hygiene (WASH) sector.

Other Contaminants

Other contaminants from sewage are hazardous for humans as well, including high nutrient concentrations. Chemicals of emerging concern (CECs) are often not removed from sewage during treatment and easily enter the marine environment. Exposure can occur through ingestion of contaminated seafood or direct contact with small concentrations in water over time. Some examples include:

• Nitrates in drinking water can cause Methemoglobinemia in children and exposure to neurotoxins generated by blue-green algal blooms can lead to Alzheimer’s symptoms. ref
• Pathogens in oysters cause 4 million cases of Hepatitis every year, while heavy metals and pharmaceuticals can impede critical bodily functions when ingested and accumulated. ref
• Pharmaceuticals, personal care products, and household cleaning products are among CECs known to cause endocrine disruption in humans, leading to negative consequences on reproductive health. ref

Certain species of algae, Pseudo-nitzchia australiis, produce domoic acid, which bioaccumulates in aquatic organisms and causes a neurological disorder called ASP in humans. The symptomatic seizures, hallucinations, memory loss, and vomiting can be brought on by exposure to small doses over time, which is typical of health hazards from other algae-borne toxins. ref

Contamination from sewage not only compounds health concerns, it jeopardizes fisheries, an essential source of protein for nutrition and livelihoods, and threatens coral reefs, which also provide food, livelihood security, coastal protection, and homes to many species essential to medical products. ref

Indirect Health Consequences

Open defecation or inadequate sanitation facilities (without lights or privacy) can be unsafe for women, creating opportunities for harassment or violence. Gender disparities resulting from inadequate sanitation are furthered when girls miss school during menstruation or women spend excess time finding clean drinking water. Sanitation interventions often require contact with sewage during collection and treatment and minimizing this contact is increasingly recognized as essential for human health.

While raw and partially treated sewage present the most significant threats to human health, hazards also exist in byproducts of treated sewage as well. Disposal of biosolids puts nearby populations at risk of inhalation or ingestion of airborne pathogens. ref

Safe sanitation has been defined by the Joint Monitoring Program (JMP) as systems that address the entire sanitation service chain. Improved sanitation includes consideration of waste beyond containment on site. Contact with sewage during collection and treatment, or because of the lack of collection and treatment, has become an important component of implementing sanitation solutions, and minimizing this contact is increasingly recognized as essential for human health. Although progress is being made, most of the world’s population does not have access to adequate sanitation to protect public health. According to the World Health Organization (WHO), nearly 6 in 10 people did have access to safely managed sanitation services in 2017. ref

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Breakdown of global access to sanitation services (left image) and the Sanitation Ladder (right image) used by the JMP to evaluate sanitation interventions. Source: opens in a new windowWHO and UNICEF