Aluminum is highly abundant in the environment and low-dose exposure is common. According to the Agency for Toxic Substances and Disease Registry (ATSDR) toxicological profile, oral exposure aluminum is generally not harmful. However, overexposure to aluminum is associated with Alzheimer's disease. People with certain kidney diseases may be prone to retaining excess aluminum in their body.

Regulation: The USEPA defines a secondary MCL of 0.05 to 0.2 mg/L for aluminum primarily because of taste, smell, and color associated with aluminum in drinking water. The Navajo Nation sets an agricultural water supply standard for acid-soluble aluminum of 20,000 μg/L. The USEPA also defines a regional screening level (RSL) for scenarios where a hiker or camper may come in contact with increased levels of aluminum in soil, sediment, or surface water of 170,000 μg/L.

Cadmium is an environmental metal most often associated with zinc, lead, and copper ore. It is also commonly found in batteries and can be introduced into the environment via industrial discharge and waste disposal. According to the Agency for Toxic Substances and Disease Registry (ATSDR) toxicological profile cadmium is associated with kidney disease and damage to lungs and the nasal cavity.

Regulation: Both the Navajo EPA and USEPA set an MCL for cadmium in drinking water at 5 μg/L. The EPA camper/recreational RSL is 83 μg/L. The Navajo Nation sets the limit for cadmium in both agricultural and livestock water supplies at 50 μg/L.

Cadmium is an environmental metal most often associated with zinc, lead, and copper ore. It is also commonly found in batteries and can be introduced into the environment via industrial discharge and waste disposal. According to the Agency for Toxic Substances and Disease Registry (ATSDR) toxicological profile cadmium is associated with kidney disease and damage to lungs and the nasal cavity.

Regulation: Both the Navajo EPA and USEPA set an MCL for cadmium in drinking water at 5 μg/L. The EPA camper/recreational RSL is 83 μg/L. The Navajo Nation sets the limit for cadmium in both agricultural and livestock water supplies at 50 μg/L.

Arsenic is a common metalloid in the environment. Inorganic arsenic is often colocated with mining activities, specifically coal and gold, but also with uranium extraction and processing. People may often come into contact with different forms of arsenic through the air they inhale, the food they eat, and the water that they drink. Some areas have higher levels of naturally occurring arsenic that may infiltrate groundwater and surface water supplies. Arsenic is listed in the Agency for Toxic Substances and Disease Registry (ATSDR) toxicological profile as a carcinogen that is implicated in numerous adverse health outcomes and even death in high doses.

Regulation: Both the Navajo EPA and the USEPA set an MCL for arsenic in drinking water at 10 μg/L. The EPA camper/recreational RSL is 50 μg/L. The Navajo Nation sets the limit for arsenic concentration in agricultural water supplies at 2000 μg/L and at 200 μg/L for livestock watering.

Copper is an abundant chemical element in the earth's crust associated with mining and corrosion of household water pipes. It is an essential nutrient found in many food sources. However, according to the Agency for Toxic Substances and Disease Registry (ATSDR) toxicological profile, excess buildup of copper in humans is associated with Wilson's disease, Indian childhood cirrhosis, and other disorders of the liver.

Regulation: Neither the Navajo EPA nor the USEPA set an MCL for copper, but define an MCL goal of 1.3 mg/L. The EPA camper/recreational RSL is 67 mg/L. The Navajo Nation sets the limit for copper in agricultural water at 200 μg/L and at 500 μg/L for livestock water supplies.

Lead is a highly toxic metal distributed in ore deposits across the world. It is associated with various ore smelting and improper waste disposal that may infiltrate local water supplies. Historically, lead was used in many consumer products, including gasoline, paint, and household plumbing. Many older plumbing systems still contain lead pipes or soldered joints. According to the Agency for Toxic Substances and Disease Registry (ATSDR) toxicological profile, lead toxicity has adverse effects on every organ because lead is easily distributed throughout the entire body. Specifically, "neurological, renal, cardiovascular, hematological, immunological, reproductive, and developmental effects" are pronounced, with most concern on early neurological development.

Regulation: The USEPA sets the MCL for lead in drinking water at 0, while the Navajo EPA sets it at 15 μg/L. The EPA camper/recreational RSL is 200 μg/L. The Navajo Nation limit for lead in agricultural water is 10,000 μg/L, and 100 μg/Lfor livestock water.

Barium is most often found underground as naturally occurring ore deposits. It does not dissolve well in water, meaning that concentrations in drinking water supplies are usually low. However, some barium compounds, such as barium acetate, barium chloride, barium hydroxide, barium nitrate, and barium sulfide, do dissolve more easily but are not often found in natural formations. Because it is commonly used in oil and natural gas production some local water supplies may become contaminated. According to the Agency for Toxic Substances and Disease Registry (ATSDR) toxicological profile, barium is implicated in changes in heart rhythm and paralysis as well as other adverse health outcomes. Exposure to barium in large doses may lead to death.

Regulation: Both the Navajo EPA and USEPA set an MCL for barium in drinking water at 2 mg/L. The EPA camper/recreational RSL is 33 mg/L. The Navajo Nation does not define a limit for barium concentration in either agricultural water supplies or for livestock watering.

Iron is a highly abundant element in the earth's crust and is also an essential trace element for the health and functioning of living organisms. According to the World Health Organization humans typically require anywhere from 10 to 50 mg of iron every day. Iron is ubiquitous in water supplies worldwide. Excess iron in water often comes from deterioration of household plumbing systems, leading to discoloration and metallic taste.

Regulation: Both the Navajo EPA and the USEPA set a secondary MCL for iron of 0.3 mg/L. The EPA camper/recreational RSL is 120,000 μg/L. There are no limits for iron in agricultural or livestock water supplies.

Selenium is a naturally occurring element that is concentrated in certain pockets of the earth's crust in some rocks and soil. It's also often produced as a byproduct in copper refining. It often binds with other metals, like copper, lead, and nickel. Because of its ubiquity in many commercial products like plastics, paints, and some shampoos, it's introduced into water supplies through waste disposal. According to the Agency for Toxic Substances and Disease Registry (ATSDR) toxicological profile, selenium is an essential nutrient, though excess exposure to selenium may be associated with brittleness of the hair or nails, and though uncommon in the United States, chronic overexposure may lead to death.

Regulation: Both the Navajo EPA and the USEPA set the MCL for selenium in drinking water at 0.05 mg/L. The EPA camper/recreational RSL is 830 μg/L. The Navajo Nation limit for selenium in agricultural water is 20 μg/L, and 50 μg/L for livestock water.

Uranium is a naturally occurring radioactive element found in deposits across the earth's crust. Today, enriched uranium is mainly used as fuel for nuclear power generation. It is distributed throughout the environment primarily through wind and water movement. It can be taken up into plants through root systems. Abandoned uranium mines (AUMs) across the Navajo Nation may be inadequately reclaimed, increasing the likelihood of uranium mobility through the environment. Drinking water is the primary source of uranium exposure. According to the Agency for Toxic Substances and Disease Registry (ATSDR) toxicological profile, uranium exhibits significant adverse effects on kidneys. Animal studies show uranium residence in other organs, such as brain tissue. Some uranium compounds may cause skin irritation.

Regulation: Both the Navajo EPA and USEPA set the MCL for uranium in drinking water at 30 μg/L. The EPA camper/recreational RSL is E-04 mg/kg-day, based on the ATSDR Minimal Risk Level (MRL) for exposure to uranium soluble salts. There is currently no numeric standard limit for uranium in either agricultural or livestock water supplies.