Impacts on Human Health

Pathogens from human waste spread diseases to people through contaminated drinking water, food grown in contaminated soils, seafood harvested from contaminated waters, and bathing and recreating in polluted waters. Infectious diseases from exposure to human waste include bacterial salmonella, parasitic giardia, and hookworm, among others. Exposure can also lead to infections in the ears, eyes, or chest and topical ailments, such as rashes and skin infections. ref

Sewage contamination warning sign on a beach in San Diego County, California. Photo © Brian Auer

Pathogens and Infectious Disease

Diarrheal diseases, such as rotavirus, cholera, and typhoid, are the dominant health concern related to wastewater pollution, causing 1.6 million deaths in 2017. ref Symptoms include severe dehydration and malnutrition and impairing children’s growth and mental development. ref The result can be lifelong health complications and damaging consequences for entire communities. See the case study from Bavu and Namaqumaqua villages in Fiji detailing the implementation of sanitation systems to address typhoid outbreaks and other impacts of wastewater pollution.

Pathogens in oysters and other shellfish cause 4 million cases of Hepatitis A and E every year, with roughly 40,000 deaths and another 40,000 cases of long-term disability from chronic liver damage. ref In a recent study along the coast of Myanmar, 5,459 bacterial pathogens in oyster tissue, marine sediments, and seawater were identified. ref Researchers reported that 51% of the pathogens found in the oyster samples were known to be detrimental and of emerging concern to human health. Contact with human waste represents an urgent challenge particularly in developing areas, and has led to the development of the Water, Sanitation, and Hygiene (WASH) sector.

Antimicrobial Resistance

The increase in antibiotic-resistant pathogens, or “superbugs,” is probably the most concerning human health impact we face related to wastewater pollution. Antimicrobial resistance is responsible for 700,000 deaths annually, a number that is growing because of poor antibiotic stewardship (i.e., over-prescribing antibiotics), lack of sanitation, insufficient wastewater treatment, and discharge into the environment. ref Superbugs originate from the overuse of antibiotics to treat an illness. As the resistant microbes reproduce, the population develops a higher resistance to antibiotics. If not properly treated, these new superbugs make their way into the environment. It is a dangerous feedback loop of disease, antibiotics, commingling, and exposure. Improving sanitation and wastewater treatment is a critical component of addressing the superbug threat because wastewater treatment plants can be a place where this resistance develops.

Other Contaminants

In addition to pathogens, other components of wastewater—like high nutrient concentrations, heavy metals, and contaminants of emerging concern (CECs) are hazardous to people. Examples of CECs and impacts to people:

• Heavy metals can be ingested when people eat fish and shellfish. Over time, metals bioaccumulate and cause damage to organs and interfere with critical bodily functions. ref
• Pharmaceuticals, personal care products, and household cleaning products can disrupt the endocrine system, leading to negative consequences on reproductive health. ref
• Karenia brevis, the marine dinoflagellate that causes red tides, produces brevetoxins that can disperse as fine particles in the air. These toxins have been associated with increased incidence of asthma, and a 40% increase in emergency room admissions for gastrointestinal disease during red tide events. ref
• Nitrates in drinking water can cause Methemoglobinemia in children, where the body produces excess methemoglobin (a form of hemoglobin) and cannot deliver oxygen effectively. Recent studies have linked nitrates in drinking water to colon, ovarian, thyroid, kidney, and bladder cancer in adults. ref In fact, numerous studies have shown that increased risk of cancer occurs with nitrates at levels below the U.S. standard of 10 parts per million. ref A Danish study reported increased risk of colon cancer with nitrate levels above 3.87 parts per million. ref
• Pseudo-nitzschia australiis, a type of algae, produces domoic acid that bioaccumulates in aquatic organisms and causes a neurological disorder called Amnesic Shellfish Poisoning (ASP) in humans. Like many other algae-borne toxins, small doses over time eventually cause symptoms. In the case of ASP, this includes seizures, hallucinations, memory loss, and vomiting. ref

In addition to making people sick, these contaminants jeopardize fisheries and coral reefs, causing further harm to people who depend on them for food, livelihoods, and coastal protection.

Indirect Health Consequences

Open defecation and unsafe sanitation facilities (without lights or privacy) are especially concerning 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.

While raw human waste and partially treated wastewater present the most significant threats to human health, hazards also exist in byproducts of treated wastewater 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 World Health Organization 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 human waste 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.