106Drinking Water Standards
The US Environmental Protection Agency is responsible for establishing maximum contaminant
levels for drinking water. These standards are expressed as MCL (Maximum Contaminant Level).
In most cases, this measurement is expressed as milligrams per liter of water (mg/l) or as parts per
million (ppm).
In general terms, inorganic compounds are those materials that do not contain carbon. These
compounds are often able to be dissolved in water. For example, dissolved gases such as nitrogen,
oxygen, radon, and methane can be classified as inorganic compounds.
In addition to dissolved gases, some metals may be present in water as well. Some of these metals
can be hazardous to human health, and may be introduced into water either naturally or through
man-made activities.
Some of the more common metals include arsenic and aluminum which the EPA has established
a MCL of no more than.05. Lead with a MCL of.015. Mercury MCL of.002. In addition, zinc, calcium,
sodium, magnesium, potassium, and copper, all with a 1.3 MCL.
Lead, mercury, and arsenic can be dangerous to human health even at low concentrations, and as
mentioned above can be introduced to our water from a variety of sources, including old pipes and
lead solder.
Conversely, some of the other inorganic compounds such as sodium, potassium, calcium, and
magnesium are important to our overall health and well-being.
Another class of inorganic compounds are known as negative ions. These include substances such
as fluoride: MCL 4.0 PPM (parts per million). Chloride and nitrate: MCL 10.0 ppm. Nitrite MCL 1.0.
Sulfate, phosphate, carbonate, and cyanide: MCL 0.2
Inorganic Chemistry
Inorganic chemistry is the study of the synthesis and behavior of inorganic and organometallic
compounds. This field covers all chemical compounds except the myriad organic compounds
(carbon based compounds, usually containing C-H bonds), which are the subjects of organic
chemistry.
The distinction between the two disciplines is far from absolute, and there is much overlap, most
importantly in the sub-discipline of organometallic chemistry. It has applications in every aspect of
the chemical industry–including catalysis, materials science, pigments, surfactants, coatings,
medicine, fuel, and agriculture.