Published By: Water Quality
Overview
The incidence of waterborne diseases has been greatly reduced since the widespread implementation of drinking water disinfection. While a measurable public health benefit has been achieved, other potential risks may have been introduced.
The presence of chloroform and other trihalomethanes (THMs) in finished drinking water was first associated with the chlorination of drinking water in 1974. It was discovered that in addition to killing microorganisms, disinfectants react with organic and inorganic substances naturally present in the water to produce a variety of disinfection by-products (DBPs), which include THMs. The DBPs associated with chlorination are THMs, haloacetic acids, haloacetonitriles and halopicrins. Chlorite and chlorate are by-products of chlorine dioxide disinfection, while ozonation may result in bromate formation. Nitrosodimethylamine (NDMA) is a by product of chlorination and chloramination.
Certain DBPs have been shown to be detrimental to health in laboratory animal studies. As a result the Environmental Protection Agency (EPA) regulated the most prevalent DBPs, the trihalomethanes, in 1979, setting the limit at 100 mg/L. The limits have since been revised with the promulgation of the Stage 1 Disinfectants and Disinfection Byproduct Rule in December 1998. The trihalomethane limit has been reduced to 80 ug/L and limits of 60 ug/L for haloacetic acid, 1.0 mg/L for chlorite and 10 ug/L for bromate have been introduced. While haloacetonitriles, halopicrins, chlorate and NDMA have been identified as health hazards, further research needs to be conducted prior to identifying appropriate regulatory levels. It is important that a balance be achieved between reducing exposure to DBPs and maintaining control of waterborne diseases through regulatory efforts.
To meet the stricter regulations, the San Francisco Public Utilities Commission (SFPUC) has converted its drinking water disinfectant from chlorine to chloramine. The conversion has effectively lowered THM formation, while continuing to maintain public health protection. The conversion from chlorine to chloramine took place in February 2004.
The following fact sheets describe the different types of DBPs and the potential health risks associated with each of them. The DBPs discussed are as follows:
- Bromate
- Chlorate/Chlorite
- Haloacetic acids
- Haloacetonitriles
- Halopicrins
- Trihalomethanes
- Nitrosodimethylamine
For Further Information
Follow the links below for information on the following topics:
- EPA Stage 1 Disinfectant and Disinfection By Product Rule Summary
- American Water Works Association (AWWA) Chlorine Disinfectants/Disinfectant By-Products (DBPs) Fact Sheet
- Call the SFPUC Water Quality Bureau for water quality information (650-652-3127 or 877-737-8297)
- Call the Environmental Protection Agency (EPA) Safe Drinking Water Hotline for information on water quality and associated regulations (800-426-4791)
- Call the SFPUC Water Quality Bureau for water quality information (650-652-3127 or 877-737-8297)
- Call the Environmental Protection Agency (EPA) Safe Drinking Water Hotline for information on water quality and associated regulations (800-426-4791)
- Call the SFPUC Water Quality Bureau for water quality information (650-652-3127 or 877-737-8297)
- Call the Environmental Protection Agency (EPA) Safe Drinking Water Hotline for information on water quality and associated regulations (800-426-4791)
- Call the SFPUC Water Quality Bureau for water quality information (650-652-3127 or 877-737-8297)
- Call the Environmental Protection Agency (EPA) Safe Drinking Water Hotline for information on water quality and associated regulations (800-426-4791)
- Call the SFPUC Water Quality Bureau for water quality information (650-652-3127 or 877-737-8297)
- Call the Environmental Protection Agency (EPA) Safe Drinking Water Hotline for information on water quality and associated regulations (800-426-4791)
- Call the SFPUC Water Quality Bureau for water quality information (650-652-3127 or 877-737-8297)
- Call the Environmental Protection Agency (EPA) Safe Drinking Water Hotline for information on water quality and associated regulations (800-426-4791)
Bromate
Bromate is a chemical formed in drinking water disinfected with ozone. Bromate has not been detected in San Francisco Public Utilities Commission (SFPUC) drinking water. The SFPUC uses ozone disinfection only at the Harry Tracy Water Treatment Plant (HTWTP).
What is Bromate?
Bromate is a chemical compound containing bromine. It is a by-product of disinfection mostly associated with ozonation of bromide-containing waters.
What are the Health Effects of Bromate?
Bromate poisoning causes abdominal pains, hearing impairment, kidney failure and at high enough doses, may cause death. Animal studies have also shown that bromate is mutagenic and carcinogenic to the kidneys in particular.
How may I be Exposed to Bromate?
Bromates are found in disinfected drinking supplies where ozone or a combination of ozone and hydrogen peroxide is used as a method of disinfection. The level of bromate is dependant on the amount of bromide found in the source water, the dosage of ozone, and the pH of the water.
Are the Levels of Bromate in Drinking Water Dangerous to my Health?
Concentrations of bromate found in water disinfected with ozone or a combination of ozone and hydrogen peroxide range from less than 1 microgram per liter (µg/L) to over 10 µg/L. The Environmental Protection Agency (EPA) regulations limit bromate to 10 µg/L.
For Further Information
Chlorate/Chlorite
Chlorate and chlorite are chemicals found in disinfected drinking water. Levels of chlorate and chlorite found in treated water from the San Francisco Public Utilities Commission (SFPUC) are generally below 0.03 mg/l. This is well below the regulatory limit for chlorite of 1.0 mg/l.
What is Chlorate/Chlorite?
Chlorate and chlorite are inorganic compounds that form during the degradation of sodium hypochlorite (chlorine). They also are used to generate chlorine dioxide, an alternative disinfectant to chlorine.
What are the Health Effects of Chlorate/Chlorite?
Exposure to chlorate and chlorite have both been shown to have adverse effects on the blood. Chlorate has additional health effects including abdominal pain, diarrhea, coma, and at high enough levels, will cause death. Further research needs to be conducted to determine the mutagenic and carcinogenic potential of chlorate and chlorite.
How may I be Exposed to Chlorate/Chlorite?
Chlorate and chlorite are found in disinfected drinking supplies where either sodium hypochlorite or chlorine dioxide is used as the method of disinfection. The levels vary considerably depending on water quality, the concentration of sodium hypochlorite, and the method used to form chlorine dioxide.
Are the Levels of Chlorate/Chlorite in Drinking Water Dangerous to my Health?
In December 1998, the Environmental Protection Agency (EPA) introduced regulations that limit the total level of chlorite to 1.0 ppm. The State action level for chlorate is 0.8 mg/L.
For Further Information
Haloacetic Acids
Haloacetic acids (HAAs) are chemicals found in disinfected drinking water. Levels of five HAAs found in treated water from the San Francisco Public Utilities Commission (SFPUC) ranged between 10 to 29 micrograms per liter (µg/L) in 2001. This is well below the regulatory limit of 60 µg/L for the total offive HAAs.
What are Haloacetic Acids?
Haloacetic acids (HAAs) are organic compounds containing chlorine and/or bromine. The compounds are formed from naturally occurring organic substances during chlorination. The HAAs of significance in disinfected water are chloroacetic acid, dichloroacetic acid, trichloroacetic acid, as well as some brominated forms.
What are the Health Effects of Haloacetic Acids?
Animal studies have demonstrated that dichloroacetic acid causes adverse effects on the brain, testes and eyes. Less is known about trichloroacetic acid and the brominated acids.
How may I be Exposed to Haloacetic Acids?
Low levels of haloacetic acids are present in chlorinated drinking water supplies due to the presence of naturally occurring organic matter, particularly amino acids, in source water which react with chlorine.
Are the Levels of Haloacetic Acids in Drinking Water Dangerous to my Health?
The Environmental Protection Agency (EPA) regulations limit the total level of HAAs (5 types) to 60 µg/L to protect from health risks. The SFPUC water is consistently well below this limit. In 2004, levels of HAAs ranged from 5 µg/L to 33 µg/L, with a maximum running average of 23 µg/L.
For Further Information
Haloacetonitriles
Haloacetonitriles are chemicals found in disinfected drinking water. Levels of haloacetonitriles found in treated water from the San Francisco Public Utilities Commission (SFPUC) are 2 µg/L and under. This is considered to be a safe level in drinking water.
What are Haloacetonitriles?
Haloacetonitriles are small organic compounds containing nitrogen, chlorine, and/or bromine. The compounds are formed from naturally occurring organic substances, particularly amino acids, during chlorination. Lower concentrations are obtained when chloramine is used instead of chlorine for disinfection. The haloacetonitriles of significance in disinfected water are dichloroacetonitrile, trichloroacetonitrile, bromochloroacetonitrile, and dibromoacetonitrile.
What are the Health Effects of Haloacetonitriles?
Little data is available on the toxicity of the haloacetonitriles, however, animal studies suggest that dichloroacetonitrile is mutagenic and therefore potentially carcinogenic.
How may I be Exposed to Haloacetonitriles?
Haloacetonitriles are found in chlorinated drinking water supplies. The levels of haloacetonitriles are dependent on the amount of naturally organic material found in the source water and the amount of chlorine used in disinfection.
Are the Levels of Haloacetonitriles in Drinking Water Dangerous to my Health?
The results of toxicity tests suggest that safe levels of haloacetonitriles in water for adults consuming 2 liters of water a day is 56 ug/L for dichloroacetonitrile and 161 ug/L for dibromoacetonitrile. No regulatory limits currently exist for haloacetonitriles, however, measurements of the levels found in disinfected water have shown that they are well below the regulatory "safe " levels.
For Further Information
Halopicrins
Chloropicrin has been detected at levels less than 1 ug/L in drinking water supplied by the San Francisco Public Utilities Commission (SFPUC). This is considered safe for drinking.
What are Halopicrins?
Halopicrins are small organic compounds containing nitrogen, chlorine, and/or bromine. The compounds are formed from naturally occurring organic substances during chlorination of water supplies, particularly those which are nitrite-rich. The halopicrin of most significance in disinfected water is chloropicrin.
What are the Health Effects of Halopicrins?
Chloropicrin can cause death at high doses. The compound is toxic through inhalation or ingestion in mammals. Inhalation results in injury to the lungs and nose. Further research is required to determine the carcinogenic potential of chloropicrin at low concentration exposure.
How may I be Exposed to Halopicrins?
Halopicrins are found in chlorinated drinking water supplies. The levels of halopicrins are dependent on the amount of naturally organic material found in the source water and the amount of chlorine used in disinfection. Ozonation prior to chlorination increases the levels of chloropicrin.
Are the Levels of Halopicrins in Drinking Water Dangerous to my Health?
The toxicity and carcinogenicity of halopicrins at levels found in disinfected water needs to be researched further to determine a level that is safe for human consumption. No regulatory limits currently exist for halopicrins, however, measurements of the levels found in disinfected water have shown that they are usually less than 1 mg/L.
For Further Information
Trihalomethanes
Trihalomethanes (THMs) are chemicals found in disinfected drinking water. Since conversion from chlorine to chloramine disinfection in February 2004, levels of THMs in treated water have been significantly reduced. For example, in 2001, prior to chloramine use, total THMs found in treated water from the SFPUC ranged between 42 and 99 micrograms per liter (ug/L), with the average being 82 ug/L. During the first half of 2005, after chloramines had been used for one year, total THMs in treated water ranged from 16 to 50 ug/L, with an average of 30 ug/L. EPA regulations limit the total level of THMs to 80 ug/L.
What are Trihalomethanes?
Trihalomethanes (THMs) are small organic compounds similar in structure to methane, but also containing chlorine and/or bromine. The compounds are the major by-products of chlorine disinfection of water supplies. They are formed when naturally occurring organic substances react with chlorine used to disinfect drinking water. The trihalomethanes of significance in disinfected water are chloroform, dichlorobromomethane, chlorodibromomethane, and bromoform.
What are the Health Effects of THMs?
The health effects of THMs are unclear. Studies of human populations have indicated a slightly higher incidence of bladder and colon cancer in areas where the drinking water has been chlorinated. Other studies, however, have not shown an increased risk of cancer. While animal studies have shown mutagenic and carcinogenic potential of THMs, it has been suggested that these results are unreliable since the animals are exposed to THM levels 10,000 times greater than humans are exposed to.
Some epidemiological studies have found associations between adverse reproductive outcomes and consumption of drinking water high in THMs, and some have not detected the associations. Studies continue to be conducted to better define whether there is a link between consumption of drinking water high in THMs and the risk of low birth weight or other adverse effects on pregnancy.
How may I be Exposed to THMs?
THMs are found in disinfected drinking water supplies. The levels of THMs are dependent on the amount of naturally occurring organic material found in the source water and the amount of chlorine used in disinfection.
Are the Levels of Trihalomethanes in Drinking Water Dangerous to my Health?
Several epidemiological studies have suggested a weak association between exposure to chlorinated surface water and certain cancers, and reproductive and developmental effects. Because of the large population exposed to chlorinated drinking water, the health risks associated with THMs, even if small, need to be taken seriously. For this reason the limit for THMs was reduced from100 µg/L to 80 µg/L under the Stage 1 Disinfectant and Disinfection By-Products Rule. By converting from chlorine to chloramine disinfection in early 2004, the SFPUC reduced total THMs to less than 30 µg/L, well below the Environmental Protection Agency’s standard for drinking water.
For Further Information
n-Nitrosodimethylamine (NDMA)
What is NDMA?
n-Nitrosodimethylamine (NDMA) can be a byproduct of either chlorination or chloramination, but drinking water is not a major source of exposure to NDMA. Most NDMA exposure is from foods and consumer products.
How may I be exposed to NDMA?
NDMA has been detected in drinking waters typically at extremely low levels of 10 parts per trillion (ppt). A study conducted by the California Department of Health Services in 1999 and 2000 found the highest level of NDMA in treated disinfected surface waters at 60 ppt (in one sample). In that study, the majority of the concentrations of NDMA were below 10 ppt (in more than 95% of the samples collected), including those from the SFPUC water system taken in 2000, which did not have any detectable concentrations of NDMA at all (below 2 ppt). A post chloramine conversion monitoring (April 2004) showed only one out of 8 locations with a detectable NDMA (detection limit of 2 ppt). That location had an NDMA level of 4 ppt.
The biggest sources of human exposure to NDMA are tobacco smoke, chewing tobacco, bacon and other cured meats, beer, fish, cheese, toiletries, shampoos, cleansers, interior air of cars, and household pesticides. In addition, NDMA can form in the stomach during digestion of foods or drugs that contain alkylamines, which are naturally occurring compounds.
Why are some groundwater supplies reporting NDMA contamination?
NDMA was historically used in the production of rocket fuel and groundwaters were impacted in some areas of Southern and Northern California where NDMA was used in the aerospace industry. In these cases of groundwater contamination the potable water wells were taken out of service.
Is NDMA toxic?
At very high levels—5,000,000 to 50,000,000 ppt—NDMA may cause liver disease in test animals.
Can NDMA cause cancer in people?
The EPA has classified NDMA as a Class B2 probable human carcinogen. This means that there is evidence of an association with tumors from studies in animals but not humans.
Are there regulations governing NDMA in water?
The US Environmental Protection Agency does not have a regulation for NDMA. However, the level of risk to protect from possible cancer (1 in 100,000 probability) due to chronic exposure has been estimated at 7 ppt. The California Department of Health Services set the drinking water action level at 10 ppt. Currently SFPUC lab techniques allow for detection of NDMA at a level of 2 ppt.
What are the current levels of NDMA in our water?
All NDMA monitoring results (voluntary quarterly monitoring) in the SFPUC water system have been below the California Department of Public Health Notification Level of 10 ng/L (parts per trillion), and specifically NDMA has been consistently not detected (below 2 ng/L detection limit) in any chlorinated or chloraminated Hetch Hetchy water source samples
Does the SFPUC currently monitor for NDMA in our water?
The SFPUC has initiated new quarterly monitoring program for NDMA now that the switch to chloramine has been completed. It is not anticipated that high levels will be observed, because of our very high quality water source and treatment practices.
For Further Information
· Call the SFPUC Water Quality Bureau for water quality information (650-652-3127 or 877-737-8297)
- Call the San Francisco Department of Public Health, Dr. June Weintraub at (415) 252-3973
- Call the State of California Department of Health Services, Dr. Kalyanpur Baliga at (510) 540-2153
· Call the Environmental Protection Agency (EPA) Safe Drinking Water Hotline for information on water quality and associated regulations (800-426-4791)
· Follow the links below for additional information on NDMA:
o California Department of Public Health NDMA Overview
o Agency for Toxic Substances and Disease Registry Fact Sheet on NDMA
