Published By: Water Quality
The following fact sheets describe selected organic chemicals and the potential health risks associated with each of them.
Benzene
Benzene is a chemical that may be found in some private or public drinking water supplies. No detectable levels of benzene have been found in San Francisco Public Utilities Commission (SFPUC) water supply or treated water.
What Is Benzene?
Benzene is a naturally occurring substance produced by volcanoes and forest fires and present in many plants and animals, but benzene is also a major industrial chemical made from coal and oil. As a pure chemical, benzene is a clear, colorless liquid. In industry, benzene is used to make other chemicals, as well as some types of plastics, detergents, and pesticides. It is also a component of gasoline.
How Might I Be Exposed to Benzene?
The three main types of exposure to benzene are environmental, consumer product, and occupational. Without question, the greatest possibility for high-level exposures is in the workplace. However, most people are exposed to benzene in tobacco smoke, automobile exhaust or pumping gasoline.
Environmental sources of benzene include gasoline stations, vehicle exhaust fumes, tobacco smoke, underground storage tanks that leak, wastewater from industries that use benzene, chemical spills, groundwater next to landfills containing benzene, and tainted drinking water.
How Does Benzene Get into My Body?
Because benzene evaporates very quickly, the most common exposure to benzene comes from breathing air containing benzene. Very small amounts of benzene are found in some foods, such as canned beef, and in contaminated drinking water.
How Can Benzene Affect My Health?
Benzene is harmful, especially to the tissues that form blood cells. How benzene affects your health would depend on how much you are exposed to and how long you are exposed to it. From overwhelming human evidence and supporting animal studies, the U.S. Department of Health and Human Services has determined that benzene is carcinogenic. Leukemia (cancer of the tissues that form the white blood cells) and subsequent death from cancer have occurred in some workers exposed to benzene for periods of less than 5 and up to 30 years. Long-term exposures to benzene may affect normal blood production, possibly resulting in severe anemia and internal bleeding.
What Levels Protect Human Health?
The Environmental Protection Agency (EPA) set the maximum permissible level in drinking water at 5 parts of benzene per billion parts of water (ppb). California Public Health Department (CADPH) has set a 1.0 ppb limit for drinking water. The Occupational Safety and Health Administration's (OSHA) legally enforceable limit for inhalation is an average of 1.0 ppm over the standard 8hour workday, 40hour workweek.
For Further Information
- Call the SFPUC Water Quality Bureau for water quality information (650-652-3127 or 877-737-8297)
- Call the Agency for Toxic Substances and Disease Registry (ATSDR) Information Center for information on benzene (800-232-4636)
- 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 benzene
Methyl tertiary butyl ether (MTBE) is a chemical that may be found in some private or public drinking water supplies. The San Francisco Public Utilities Commission (SFPUC) has tested its drinking water for the presence of MTBE. No detectable levels of MTBE have been found in drinking water supplied by the SFPUC
.
What is MTBE?
MTBE is a colorless, flammable liquid with a strong odor. It does not occur naturally but is produced in very large amounts (9.5 billion pounds in 1995) in the United States. MTBE is added to gasoline to improve combustion and to reduce harmful carbon monoxide emissions. It is added to gasoline to improve the overall quality of air to help cities meet air quality standards mandated by EPA.
How Might I be Exposed to MTBE?
Exposure to MTBE can occur in the workplace or in the environment following releases to air, water, land, or groundwater. Exposure can also occur when people:
- are in places where gasoline is being pumped into vehicles,
- fill gasolinepowered home maintenance equipment,
- live near bulk gasoline loading and unloading facilities, or
- live near facilities that can leak gasoline from underground storage containers.
MTBE enters the body when breathed in with contaminated air or when consumed with contaminated food or water. It is also absorbed through skin contact. MTBE does not remain in the body due to its breakdown and removal.
What Happens to MTBE in the Environment?
MTBE evaporates when exposed to air. It dissolves when mixed with water. Most direct releases of MTBE to the environment are to air. MTBE also evaporates from water and soil exposed to air. Once in air, it is expected to break down to other chemicals.
How Does MTBE Affect Human Health?
Effects of MTBE on human health and the environment depend on how much MTBE is present and the length and frequency of exposure. Effects also depend on the health of a person or the condition of the environment when exposure occurs.
Human health effects associated with exposure to smaller amounts of MTBE over long periods of time are not known. Laboratory studies show that repeat exposure to large amounts of MTBE in air causes kidney damage and adversely affects the developing fetus of animals. Studies also show that lifetime exposure to MTBE in air causes cancer in animal.
For Further Information
- 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)
- Contact the following federal agencies for information on MTBE
- Agency for Toxic Substances and Disease Registry (ATSDR) (800-447-1544)
- American Industrial Hygiene Association (703- 849-8888)
- Consumer Product Safety Commission (301-504-7923)
- National Institute for Environmental Health Sciences (EnviroHealth Clearinghouse) (919-541-3345)
- Follow the links below for more information on MTBE
What is Perchlorate? Perchlorate is an industrial mineral used principally as an oxidizer in solid rocket fuel. It is also produced for a variety of other industrial uses, including the manufacture of air bag inflators, in leather tanning, electroplating, and rubber manufacturing. Perchlorate can occur naturally, but it is only found in very rare geologic deposits. What are the Health Effects of Perchlorate? Perchlorate disrupts the function of the thyroid gland by interfering with iodide uptake. This interference can lead to developmental defects and thyroid tumors. The Environmental Protection Agency completed a draft toxicity profile for perchlorate in January 2003 that discusses these potential health effects in detail. How may I be Exposed to Perchlorate? Perchlorate exposure can occur through drinking contaminated water or through occupational exposure in settings where perchlorate is used. Exposure may also occur through ingestion of lettuce that was irrigated with water that has been contaminated by perchlorate. Is there Perchlorate in San Francisco's drinking water? The SFPUC has monitored all source water reservoirs in the past years, and perchlorate has not been found in San Francisco's drinking water. For Further Information
Perchlorate
Trichloroethylene
Trichloroethylene is a chemical that may be found in some private or public drinking water supplies. The San Francisco Public Utilities Commission (SFPUC) has tested its drinking water for the presence of trichloroethylene. No detectable levels of trichloroethylene have ever been found in drinking water supplied by the SFPUC. Due to the highly protected nature of our surface water supplies, the SFPUC would never expect to find trichloroethylene in our drinking water. For those who still may have concerns related to water or other exposures, we have provided the following information.
What is Trichloroethylene?
Trichloroethylene is a colorless, non-flammable liquid with a somewhat sweet odor and a sweet burning taste. It does not occur naturally. Trichloroethylene is used as a solvent to degrease metal parts and is an ingredient in adhesives, paint remover, typewriter correction fluids and spot removers. .
How Might I be Exposed to Trichloroethylene?
Exposure to trichloroethylene typically occurs when people breathe air which has been contaminated with trichloroethylene vapors. This type of exposure can happen among people whose work involves manufacturing trichloroethylene or using it to wash paint or grease from skin or equipment. Occupational activities may also lead to exposure to trichloroethylene through the skin by direct contact with products that contain trichloroethylene. Among people who do not work with trichloroethylene compounds, exposure may occur by breathing in vapors from some household products such as spot removers and typewriter correction fluid. If water is contaminated with trichloroethylene, people may be exposed if they drink contaminated water, or by breathing in vapors or through their skin while showering, bathing, or swimming.
What Happens to Trichloroethylene in the Environment?
Trichloroethylene dissolves a little in water. While it quickly evaporates from contaminated surface water forming a vapor in the air, trichloroethylene can remain in ground water for extended periods of time. Trichloroethylene may stick to particles found in water which eventually may settle to the bottom sediment. Trichloroethylene does not easily evaporate from soil where it may stick to particles and remain for a long time. Trichloroethylene does not build up significantly in plants or animals.
How Does Trichloroethylene Affect Human Health?
Inhalation of air containing low levels of trichloroethylene vapors may cause minor symptoms including headache, nausea, dizziness, clumsiness, drowsiness, and other effects like those of being drunk. However, high levels or extended periods of exposure may cause impaired heart function, unconsciousness, nerve damage or death.
Studies suggest that trichloroethylene levels commonly found in drinking water may be associated with impaired fetal development, and may affect male and female fertility. While exposure to small amounts is not likely sufficient to cause liver toxicity or cancer in humans, occupational exposure to high doses can result in increased rates. There is also strong evidence suggesting that exposure to high doses of trichloroethylene is associated with increased rates of kidney cancer. Individuals with genetic predisposition may also be at increased risk for autoimmune disease following low to high levels of exposure.
For Further Information
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)
Contact the following federal agencies for information on Trichloroethylene
o Agency for Toxic Substances and Disease Registry (ATSDR) (800-447-1544)
o American Industrial Hygiene Association (703-
o Consumer Product Safety Commission (301-504-0990)
o National Institute for Environmental Health Sciences (EnviroHealth Clearinghouse) (919-541-3345)
Follow the links below for more information on Trichloroethylene
o EPA Trichloroethylene Fact Sheet (http://www.epa.gov/safewater/dwh/c-voc/trichlor.html)
o ATSDR Trichloroethylene Fact Sheet (http://www.atsdr.cdc.gov/tfacts19.html )
o California Department of Health Services (DHS) Trichloroethylene in California Drinking Water Information (http://www.dhs.ca.gov/ohb/HESIS/tce.htm)
o The National Academies Press: Assessing the Human Health Risks of Trichloroethylene: Key Scientific Issues (http://www.nap.edu/catalog/11707.html)
