From the Guidelines
Tap water can be contaminated by a wide range of substances, including microorganisms, chemicals, pharmaceuticals, and physical contaminants, which can enter the water supply through various natural and human-caused pathways, as highlighted in a recent study 1.
Contaminant Sources
These contaminants can originate from:
- Natural sources, such as mineral deposits that leach into groundwater
- Human-caused contamination, including industrial waste, agricultural runoff, or sewage that enters water sources
- Aging infrastructure, where old pipes can introduce lead and other metals into otherwise clean water
- Water treatment facilities that may not remove all contaminants, particularly newer chemical compounds or pharmaceuticals
- Accidents or system failures at treatment plants that can temporarily compromise water quality
Types of Contaminants
The types of contaminants that can be present in tap water include:
- Microorganisms, such as bacteria, viruses, and parasites
- Chemicals, including lead, arsenic, pesticides, and industrial chemicals
- Pharmaceuticals, such as antibiotics and other medications
- Nitrates from fertilizers
- Physical contaminants, like sediment
Entry Points for Contaminants
Contaminants can enter the water supply through multiple pathways, including:
- Direct point sources, such as effluent discharge from hospitals, industries, and wastewater treatment plants
- Indirect sources, including atmospheric deposition, catchment runoff, septic tanks, and waste dumping sites
- Aging infrastructure and water treatment facilities that may not be equipped to remove all contaminants As noted in a study on hospital effluents management 1, the presence of hazardous substances, such as disinfectants, detergents, and pharmaceutical residues, can pose a risk to public health and the environment.
Global Occurrence of Contaminants
The occurrence of emerging contaminants in water matrices is a global issue, with studies reporting their presence in various water sources, including treated wastewater, surface water, groundwater, and drinking water, as discussed in a recent review 1.
Risk Assessment
While municipal water systems in developed countries are generally safe due to treatment and testing requirements, the presence of contaminants in tap water can still pose a risk to human health, particularly for vulnerable populations, such as the elderly and young children, as highlighted in a study on the risk assessment of emerging contaminants 1.
From the Research
Contaminants in Tap Water
The following contaminants can be found in tap water:
- Bacteria, such as Escherichia coli and Clostridium perfringens 2
- Viruses, including norovirus and hepatitis A virus 2, 3
- Parasites, like Cryptosporidium parvum and Giardia intestinalis 4, 2
- Algae, which can produce toxins 4
- Chlorine gas, which can be present as a disinfectant byproduct 4
Entry Points for Contaminants
Contaminants can enter tap water through various means, including:
- Inadequate water treatment processes, allowing bacteria, viruses, and parasites to pass through 2
- Contamination of water sources, such as lakes, rivers, or groundwater 3
- Leaks or cracks in water distribution systems, enabling external contaminants to enter the water supply 3
- Ineffective disinfection methods, which may not fully eliminate pathogens from the water 5, 6
Factors Influencing Contaminant Presence
Several factors can influence the presence and diversity of contaminants in tap water, including:
- Residual disinfectant use, such as chlorine or chlorine dioxide, which can affect the types and amounts of contaminants present 3, 5, 6
- Environmental conditions, like temperature and pH, which can impact the survival and growth of microorganisms in the water 5
- Water treatment processes and technologies, which can either remove or introduce contaminants into the water supply 2, 3