Table 1.
The 2022 World Health Organization (WHO) drinking-water guideline values (GVs), health-based values (HBVs), reference values (RVs), and aesthetic values (AVs) for inorganic contaminants [18].
These values are in milligrams per liter (mg/L) and micrograms per liter (μg/L). Point of Departure (POD) studies are identified as provided in WHO background documents.
Fig 1.
A chronology of World Health Organization (WHO) standard values (SVs) and guidelines values (GVs) for selected inorganic contaminants [7–18].
Fig 2.
Frequency of publication years for the point of departure (POD) studies or other references identified as the bases for World Health Organization guideline values (GVs), health-based values (HBVs), reference values (RVs), and aesthetic values (AVs) [7–18].
Table 2.
Status of drinking water regulations for the 195 countries in this study.
For each country, information, when available, is listed for the number of inorganic chemicals regulated, the of inorganic chemical regulations exceeding World Health Organization (WHO) guideline values (GVs) [18], the year of publication of the regulations, the population in 2020 [25], the gross domestic product (GDP)/capita in United States dollars (USD) [26], the World Bank (WB) income class [108], regulatory links to other organizations or countries, the type of governmental body that released the regulation, and the type of evidence that we found for the regulation.
Fig 3.
Map of 195 countries showing their drinking water regulation status (map base: [30]).
Fig 4.
Countries with regulations for 15 or fewer inorganic contaminants in drinking water.
Fig 5.
Countries with regulations for 27 or more inorganic contaminants in drinking water.
Fig 6.
Countries with more than three exceedances of WHO GVs for inorganic contaminants in their national drinking water regulations.
Regulations classified as exceedances provide less protection than WHO GVs.
Table 3.
List of inorganic drinking water contaminants that are regulated by individual countries, along with the types of regulations and numbers of countries that have each type of regulation.
Fig 7.
A visual comparison of the 2022 World Health Organization (WHO) Guideline Values (GVs) for inorganic contaminants in drinking water to the current national drinking water standards [18].
Values are shown in milligrams/liter (mg/L) on a logarithmic scale.
Table 4.
A comparison of the 2022 World Health Organization (WHO) Guideline Values (GVs) in milligrams/liter (mg/L) for inorganic contaminants in drinking water to the current national drinking water standards [18].
Minima and maxima are listed twice, first with all values as written in sources and then with potential typographical errors removed. Country categories are compared by raw count of countries and then by percentage of world population within each category. Income differences between categories are compared using population-weighted gross domestic product (P-W GDP)/capita within each category, shown in United States dollars (USD).
Fig 8.
Percentage of 2020 world population living in countries that have regulations and whose regulations meet World Health Organization (WHO) guideline values (GVs).
Population data from the World Bank [25].
Fig 9.
Population-weighted gross domestic products (P-W GDPs) /capita in United States dollars (USD) for populations living in countries that have or do not have regulations for contaminants with World Health Organization (WHO) guideline values (GVs).
Population and GDP data are from the World Bank for 2020 [25, 26].
Fig 10.
Population-weighted Gross Domestic Products (P-W GGDPs) /capita in United States Dollars (USD) for populations living in countries whose regulations meet or exceed World Health Organization (WHO) guideline values (GVs) for inorganic contaminants.
Population and GDP data from the World Bank for 2020 [25, 26].
Table 5.
A comparison of national drinking water standards for inorganic contaminants for which the World Health Organization (WHO) has calculated Health-based Values (HBVs) or health-based Reference Values (RVs) in milligrams/liter (mg/L) but does not currently have formal Guideline Values (GVs) [18].
Minima and maxima are listed twice, first with all values as written in sources and then with potential typographical errors removed. Country categories are compared by raw count of countries and then by percentage of world population within each category. Income differences between categories are compared using population-weighted gross domestic projects (P-W GDP)/capita within each category, shown in United States dollars (USD).
Fig 11.
A visual comparison of national drinking water standards for inorganic contaminants for which the World Health Organization (WHO) provides a health-based value (HBV) but no drinking water guideline value (GV).
Values are shown in milligrams/liter (mg/L) on a logarithmic scale.
Fig 12.
Percentage of world population living in countries that have regulations and whose regulations meet World Health Organization (WHO) health-based values (HBVs) or reference values (RVs).
Population data are from the World Bank for 2020 [25].
Fig 13.
Population-weighted Gross Domestic Products (P-W GDPs)/capita in United States dollars (USD) for populations living in countries that have or do not have regulations for contaminants with World Health Organization (WHO) health-based values (HBVs) or Reference Values (RVs).
Population and GDP data from the World Bank for 2020 [25, 26].
Fig 14.
Population-weighted Gross Domestic Products (P-W GDPs)/capita in United States dollars (USD) for populations living in countries whose regulations meet or exceed (less protective than) World Health Organization (WHO) health-based values (HBVs) or health-based reference values (RVs) for inorganic contaminants.
Population and GDP data are from the World Bank for 2020 [25, 26].
Table 6.
A list of current national drinking water standards in milligrams/liter (mg/L) for inorganic contaminants that do not have 2022 World Health Organization (WHO) guideline values (GVs), health-based values (HBVs) or health-based reference values (RVs) [18].
Minima and maxima are listed twice, first with all values as written in sources and then with potential typographical errors removed. Country categories are compared by raw count of countries and then by percentage of world population within each category. Income differences between categories are compared using population-weighted gross domestic projects (P-W GDP)/capita within each category, shown in United States dollars (USD).
Fig 15.
A visual comparison of the inorganic contaminants that do not have 2022 World Health Organization (WHO) guideline values (GVs), health-based values (HBVs), or health-based reference values (RVs) [15] and appear in five or more national drinking water standards.
Values are shown in milligrams/liter (mg/L) on a logarithmic scale.
Fig 16.
Percentage of world population living in countries with regulations and whose regulations meet World Health Organization (WHO) aesthetic values (AVs).
Population data are from the World Bank for 2020 [25].
Fig 17.
Population-weighted Gross Domestic Products (P-W GDPs)/capita in United States dollars (USD) for populations living in countries with or without regulations for contaminants for which there are WHO AVs.
Population and GDP data are from the World Bank for 2020 [25, 26].
Table 7.
National regulations in milligrams/liter (mg/L) for inorganic contaminants for which the WHO has both Aesthetic Values (AVs) and Health-based Values (HBVs) [18].
Country categories are compared by raw count of countries and then by the percentage of world population within each category. Income differences between categories are compared using population-weighted gross domestic projects (P-W GDP)/capita within each category, shown in United States dollars (USD).
Fig 18.
Population-weighted Gross Domestic Products (P-W GDPs)/capita in United States dollars (USD) for populations living in countries whose regulations for contaminants with World Health Organization (WHO) aesthetic values (AVs) meet or exceed (less protective than) the WHO AVs.
Population and GDP data are from the World Bank for 2020 [25, 26].
Fig 19.
Percentage of world population living in countries with regulations for inorganic contaminants in drinking water that have no World Health Organization (WHO) guidance.
Population data are from the World Bank for 2020 [25].
Fig 20.
Population-weighted gross domestic products (P-W GDPs)/capita for populations living in countries with regulations for contaminants for which there are five or more national regulations but no World Health Organization (WHO) guidance.
Population and GDP data are from the World Bank for 2020 [25, 26].