Where does the list of regulated contaminants and allowed concentration limits or ranges come from?

The Safe Drinking Water Act (SDWA) established Federal responsibility in the area of water quality in 1974. At the Federal level, the Environmental Protection Agency (EPA) establishes water quality guidelines that state environmental agencies execute through licensing, regulation and inspection. The Texas Commission on Environmental Quality (TCEQ) administers the state program in Texas. TCEQ provides its public drinking water standards in the Chapter 290 Rules available online.

The EPA regulates drinking water contaminants, deemed as “any physical, chemical, biological or radiological substance or matter in water.” The EPA goes on to say, “Drinking water may reasonably be expected to contain at least small amounts of some contaminants. Some contaminants may be harmful if consumed at certain levels in drinking water. The presence of contaminants does not necessarily indicate that the water poses a health risk.”

There are six classifications of contaminants with a few examples of each:

  • Microorganisms, such as Legionella and Cryprosporidium
  • Disinfectants, such as chlorine, chloramine, and chlorine dioxide
  • Disinfection By-Products, such as Total Trihalomethanes and Haloacetic Acids
  • Inorganic Chemicals, such as Lead and Mercury
  • Organic Chemicals, such as Atrazine and Polychlorinated biphenyls (PCBs)
  • Radionuclides, such as Alpha and Beta particles, radium, and uranium

The EPA currently regulates allowed concentrations of about 90 total contaminants. The EPA determined these are dangerous to human health and set limits on concentrations of those contaminants. In the area of “disinfectant” contaminants, used to assure residual microorganism elimination all the way to the last customer’s tap, the EPA set both minimum and maximum concentration levels. The minimum level to ensure microorganisms are still killed; the maximum to ensure human health is not compromised.

Show All Answers

1. What is temporary change in disinfectant (TCD)?
2. What is a "chlorine burn" and is it different than "chlorine maintenance" or "TCD"?
3. Can you reduce the amount of chlorine in the water so the taste and odor isn’t as noticeable and disinfection byproducts (DBPs) are reduced?
4. What are disinfection by-products (DBP)?
5. Does Allen comply with DBP limits? How do we know tests are accurate?
6. Does our water system contain any lead pipes?
7. How does Allen regulate levels of lead and copper?
8. Where can I learn more about lead and copper in drinking water?
9. Where does the list of regulated contaminants and allowed concentration limits or ranges come from?
10. How are new contaminants selected for the list of contaminants and how are the limits established?
11. What are the guidelines on commercial flushing?
12. How can I influence water quality and safety?