Impacts on Human Health
Contamination of drinking water is the primary pathway for pathogens in human waste to spread diseases to and from people. People are also exposed to these pathogens through soils, 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 topical ailments, such as rashes, and skin infections. ref
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 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. 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, Littman and colleagues (2020) ref identified 5,459 bacterial pathogens in oyster tissue, marine sediments, and seawater. They reported that 51% of the pathogens found in the oyster samples were known to be detrimental and of emerging concern to human health.
In addition to gastrointestinal infections, opens in a new windowswimmers exposed to polluted waters are at risk for chest, ear, eye, and skin infections, as well as hepatitis.
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.
Lack of Access to Sanitation, by Region ref
|Region||Number of People without Access to Sanitation|
|Southern Asia||953 million|
|Sub-Saharan Africa||695 million|
|Eastern Asia||337 million|
|South Eastern Asia||176 million|
|Latin America and the Caribbean||106 million|
|Other areas||98 million|
Other contaminants from human waste are hazardous for humans as well, including high nutrient concentrations. Chemicals of emerging concern (CECs) are often not removed from wastewater 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:
- Heavy metals 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
- Karenia brevis, the marine dinoflagellate that causes red tides, a type of harmful algal bloom, produces brevetoxins that can aerosolize. 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 and exposure to neurotoxins generated by blue-green algal blooms can lead to Alzheimer’s symptoms. ref 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
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 wastewater 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
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 opens in a new windowpoor antibiotic stewardship (i.e., over-prescribing antibiotics), lack of sanitation, insufficient wastewater treatment, and discharge into the environment. ref Superbugs originate with illness that is treated – often liberally – with antibiotics. These antibiotics make it into wastewater, where they mingle with microbes. The antibiotics kill many microbes, while other microbes that have the genetics to resist lower doses of antibiotics, are selected for and increase in relative abundance. 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. There is a growing realization that wastewater treatment plants are a breeding ground for superbugs. ref Improving sanitation and wastewater treatment is a critical component of addressing this threat to human health.
Reducing pollution and the prevalence of superbugs also benefits ocean health. With the COVID-19 pandemic, the importance of public health in even distant places has never been more appreciated. Local or regional wastewater pollution challenges have the potential to create global health crises. Taneja and Sharma ref document an excellent example of the severity of this situation in India. Throughout the country, there has been liberal and injudicious use of antibiotics to treat many illnesses. This practice has led to one of the highest rates of resistance to antimicrobial agents used to treat humans and food animals, and to one of the highest concentrations of drug-resistant microbes in natural water bodies. Their findings are a warning to the rest of the global community, while the containment plans now being put in place (reduction in antibiotic use and ban of wastewater sludge application to agricultural fields) serve as a model of how to abate the issue.
Indirect Health Consequences
Open defecation or unsafe sanitation facilities (without lights or privacy) are particularly 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. Sanitation interventions often require contact with human waste during collection and treatment and minimizing this contact is increasingly recognized as essential for public health.
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 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. According to the World Health Organization (WHO), nearly 6 in 10 people did have access to safely managed sanitation services in 2017. ref