MadSci Network: Earth Sciences
Query:

Re: whats in our drinking water?

Date: Tue May 22 22:00:35 2001
Posted By: Luis E. Castro-Solís, Faculty, Environmental Engineering Station, Water Quality Station at University of Coahuila
Area of science: Earth Sciences
ID: 989627134.Es
Message:

Drinking Water Contaminants

Drinking water, including bottled water, may reasonably be expected to 
contain at least small amounts of some contaminants. The presence of 
contaminants does not necessarily indicate that water poses a health 
risk.  EPA sets standards for approximately 90 contaminants in drinking 
water. EPA’s standards, along with each contaminant’s likely source and 
health effects, are available at 

www.epa.gov/safewater/mcl.html

More detailed information on specific contaminants is available below: 

Microbes ~ Radionuclides ~ Inorganics ~ Volatile Organics ~ Synthetic  
Organics ~ Disinfectants ~ Disinfection Byproducts ~ MTBE ~ Health 
Advisories 



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Microbes
Coliform bacteria are common in the environment and are generally not 
harmful. However, the presence of these bacteria in drinking water is 
usually a result of a problem with the treatment system or the pipes which 
distribute water, and indicates that the water may be contaminated with 
germs that can cause disease. 

Fecal Coliform and E coli are bacteria whose presence indicates that the 
water may be contaminated with human or animal wastes. Microbes in these 
wastes can cause short-term effects, such as diarrhea, cramps, nausea, 
headaches, or other symptoms.  

Turbidity has no health effects. However, turbidity can interfere with 
disinfection and provide a medium for microbial growth. Turbidity may 
indicate the presence of disease causing organisms. These organisms 
include bacteria, viruses, and parasites that can cause symptoms such as 
nausea, cramps, diarrhea, and associated headaches. 

Cryptosporidium is a parasite that enters lakes and rivers through sewage 
and animal waste. It causes cryptosporidiosis, a mild gastrointestinal 
disease. However, the disease can be severe or fatal for people with 
severely weakened immune systems. EPA and CDC have prepared advice for 
those with severely compromised immune systems who are concerned about 
Cryptosporidium.  

Giardia lamblia is a parasite that enters lakes and rivers through sewage 
and animal waste. It causes gastrointestinal illness (e.g. diarrhea, 
vomiting, cramps). 

Radionuclides
Alpha emitters. Certain minerals are radioactive and may emit a form of 
radiation known as alpha radiation. Some people who drink water containing 
alpha emitters in excess of  EPA's standard over many years may have an 
increased risk of getting cancer. 

Beta/photon emitters. Certain minerals are radioactive and may emit forms 
of radiation known as photons and beta radiation. Some people who drink 
water containing beta and photon emitters in excess of EPA's standard over 
many years may have an increased risk of getting cancer. 

Combined Radium 226/228. Some people who drink water containing radium 226 
or 228 in excess of EPA's standard over many years may have an increased 
risk of getting cancer. 

Radon gas can dissolve and accumulate in underground water sources, such 
as wells, and in the air in your home. Breathing radon can cause lung 
cancer. Drinking water containing radon presents a risk of developing 
cancer. Radon in air is more dangerous than radon in water. 

Inorganic Contaminants
Antimony 
Asbestos 
Barium 
Beryllium Cadmium 
Chromium 
Copper Cyanide 
Mercury 
Nitrate Nitrite 
Selenium 
Thallium 
Technical fact sheets on Inorganic Contaminants 

Arsenic. Some people who drink water containing arsenic in excess of EPA's 
standard over many years could experience skin damage or problems with 
their circulatory system, and may have an increased risk of getting 
cancer. 

Fluoride. Many communities add fluoride to their drinking water to promote 
dental health. Each community makes its own decision about whether or not 
to add fluoride. EPA has set an enforceable drinking water standard for 
fluoride of 4 mg/L (some people who drink water containing fluoride in 
excess of this level over many years could get bone disease, including 
pain and tenderness of the bones). EPA has also set a secondary fluoride 
standard of 2 mg/L to protect against dental fluorosis. Dental fluorosis, 
in its moderate or severe forms, may result in a brown staining and/or 
pitting of the permanent teeth. This problem occurs only in developing 
teeth, before they erupt from the gums. Children under nine should not 
drink water that has more than 2 mg/L of fluoride. 

Lead typically leaches into water from plumbing in older buildings. Lead 
pipes and plumbing fittings have been banned since August 1998. Children 
and pregnant women are most susceptible to lead health risks. For advice 
on avoiding lead, see EPA’s lead in your drinking water fact sheet.  

Synthetic Organic Contaminants, including pesticides & herbicides
2,4-D 
2,4,5-TP (Silvex) 
Acrylamide 
Alachlor 
Atrazine  
Benzoapyrene 
Carbofuran 
Chlordane 
Dalapon 
Di 2-ethylhexyl adipate 
Di 2-ethylhexyl phthalate Dibromochloropropane 
Dinoseb 
Dioxin (2,3,7,8-TCDD) 
Diquat 
Endothall 
Endrin 
Epichlorohydrin 
Ethylene dibromide 
Glyphosate 
Heptachlor 
Heptachlor epoxide Hexachlorobenzene  
Hexachlorocyclopentadiene 
Lindane 
Methoxychlor  
Oxamyl [Vydate] 
PCBs [Polychlorinated biphenyls]  
Pentachlorophenol  
Picloram  
Simazine 
Toxaphene  
Technical fact sheets on Synthetic Organic Contaminants 

Volatile Organic Contaminants
Benzene 
Carbon Tetrachloride 
Chlorobenzene  
o-Dichlorobenzene 
p-Dichlorobenzene  
1,1-Dichloroethylene 
cis-1,2-Dichloroethylene trans-1,2-Dicholoroethylene 
Dichloromethane 
1,2-Dichloroethane 
1,2-Dichloropropane 
Ethylbenzene 
Styrene 
Tetrachloroethylene 1,2,4-Trichlorobenzene 
1,1,1,-Trichloroethane  
1,1,2-Trichloroethane 
Trichloroethylene  
Toluene 
Vinyl Chloride 
Xylenes  
Technical fact sheets on Volatile Organic Contaminants 

Disinfectants
Many water suppliers add a disinfectant to drinking water to kill germs 
such as giardia and e coli. Especially after heavy rainstorms, your water 
system may add more disinfectant to guarantee that these germs are 
killed.  

Chlorine. Some people who use drinking water containing chlorine well in 
excess of EPA's standard could experience irritating effects to their eyes 
and nose.  Some people who drink water containing chlorine well in excess 
of EPA's standard could experience stomach discomfort. 

Chloramine. Some people who use drinking water containing chloramines well 
in excess of EPA's standard could experience irritating effects to their 
eyes and nose.  Some people who drink water containing chloramines well in 
excess of EPA's standard could experience stomach discomfort or anemia. 

Chlorine Dioxide. Some infants and young children who drink water 
containing chlorine dioxide in excess of EPA's standard could experience 
nervous system effects.  Similar effects may occur in fetuses of pregnant 
women who drink water containing chlorine dioxide in excess of EPA's 
standard.  Some people may experience anemia. 

Disinfection Byproducts
Disinfection byproducts form when disinfectants added to drinking water to 
kill germs react with naturally-occuring organic matter in water. 

Total Trihalomethanes. Some people who drink water containing 
trihalomethanes in excess of EPA's standard over many years may experience 
problems with their liver, kidneys, or central nervous systems, and may 
have an increased risk of getting cancer.  

Haloacetic Acids. Some people who drink water containing haloacetic acids 
in excess of EPA's standard over many years may have an increased risk of 
getting cancer. 

Bromate. Some people who drink water containing bromate in excess of EPA's 
standard over many years may have an increased risk of getting cancer. 

Chlorite. Some infants and young children who drink water containing 
chlorite in excess of EPA's standard could experience nervous system 
effects.  Similar effects may occur in fetuses of pregnant women who drink 
water containing chlorite in excess of EPA's standard.  Some people may 
experience anemia. 



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MTBE is a fuel additive, commonly used in the United States to reduce 
carbon monoxide and ozone levels caused by auto emissions. Due to its 
widespread use, reports of MTBE detections in the nation's ground and 
surface water supplies are increasing. The Office of Water and other EPA 
offices are working with a panel of leading experts to focus on issues 
posed by the continued use of MTBE and other oxygenates in gasoline. EPA 
is currently studying the implications of setting a drinking water 
standard for MTBE. 

Health advisories provide additional information on certain contaminants. 
Health advisories are guidance values based on health effects other than 
cancer. These values are set for different durations of exposure (e.g., 
one-day, ten-day, longer-term, and lifetime). 



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