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As part of the Drinking
Water and Health pages, this fact sheet is part of a larger
publication:
National Primary Drinking Water Regulations
This is a factsheet about a chemical
that may be found in some public or private drinking water
supplies. It may cause health problems if found in amounts
greater than the health standard set by the United States
Environmental Protection Agency (EPA).
What are Nitrates/Nitrites and how are
they used?
Nitrates and nitrites are
nitrogen-oxygen chemical units which combines with various
organic and inorganic compounds. Once taken into the body,
nitrates are converted into nitrites. The greatest use of
nitrates is as a fertilizer.
Nitrate is one of the most common
groundwater contaminants in rural areas. It is regulated in
drinking water primarily because excess levels can cause
methemoglobinemia, or "blue baby" disease. Although nitrate
levels that affect infants do not pose a direct threat to older
children and adults, they do indicate the possible presence of
other more serious residential or agricultural contaminants,
such as bacteria or pesticides.
Nitrate in groundwater originates primarily from fertilizers,
septic systems, and manure storage or spreading operations.
Fertilizer nitrogen that is not taken up by plants, volatilized,
or carried away by surface runoff leaches to the groundwater in
the form of nitrate. This not only makes the nitrogen
unavailable to crops, but also can elevate the concentration in
groundwater above the levels acceptable for drinking water
quality. Nitrogen from manure similarly can be lost from fields,
barnyards, or storage locations. Septic systems also can elevate
groundwater nitrate concentrations because they remove only half
of the nitrogen in wastewater, leaving the remaining half to
percolate to groundwater.
Why are Nitrates/Nitrites being
regulated?
In 1974, Congress passed the Safe
Drinking Water Act. This law requires EPA to determine safe
levels of chemicals in drinking water which do or may cause
health problems. These non-enforceable levels, based solely on
possible health risks and exposure, are called Maximum
Contaminant Level Goals.
The MCLG for nitrates has been set at
10 parts per million (ppm), and for nitrites at 1 ppm, because
EPA believes this level of protection would not cause any of the
potential health problems described below.
Based on this MCLG, EPA has set an
enforceable standard called a Maximum Contaminant Level (MCL).
MCLs are set as close to the MCLGs as possible, considering the
ability of public water systems to detect and remove
contaminants using suitable treatment technologies.
The MCL for nitrates has been set at 10
ppm, and for nitrites at 1 ppm, because EPA believes, given
present technology and resources, this is the lowest level to
which water systems can reasonably be required to remove this
contaminant should it occur in drinking water.
These drinking water standards and the
regulations for ensuring these standards are met, are called
National Primary Drinking Water Regulations. All public water
supplies must abide by these regulations.
What are the health effects?
Short-term: Excessive levels of nitrate
in drinking water have caused serious illness and sometimes
death. The serious illness in infants is due to the conversion
of nitrate to nitrite by the body, which can interfere with the
oxygen-carrying capacity of the childs blood. This can be an
acute condition in which health deteriorates rapidly over a
period of days. Symptoms include shortness of breath and
blueness of the skin.
Long-term: Nitrates and nitrites have
the potential to cause the following effects from a lifetime
exposure at levels above the MCL: diuresis, increased starchy
deposits and hemorrhaging of the spleen.
How much Nitrates/Nitrites are
produced and released to the environment?
Most nitrogenous materials in natural
waters tend to be converted to nitrate, so all sources of
combined nitrogen, particularly organic nitrogen and ammonia,
should be considered as potential nitrate sources. Primary
sources of organic nitrates include human sewage and livestock
manure, especially from feedlots.
The primary inorganic nitrates which
may contaminate drinking water are potassium nitrate and
ammonium nitrate both of which are widely used as fertilizers.
According to the Toxics Release
Inventory, releases to water and land totaled over 112 million
pounds from 1991 through 1993. The largest releases of inorganic
nitrates occurred in Georgia and California.
What happens to Nitrates/Nitrites when
they are released to the environment?
Since they are very soluble and do not
bind to soils, nitrates have a high potential to migrate to
ground water. Because they do not evaporate, nitrates/nitrites
are likely to remain in water until consumed by plants or other
organisms.
How will Nitrates/Nitrites be detected
in and removed from my drinking water?
The regulation for nitrates/nitrites
became effective in 1992. Between 1993 and 1995, EPA required
your water supplier to collect water samples at least once a
year and analyze tem to find out if nitrates/nitrites are
present above 50 percent of their MCLs. If it is present above
this level, the system must continue to monitor this contaminant
every 3 months.
If contaminant levels are found to be
consistently above their MCLs, your water supplier must take
steps to reduce the amount of nitrates/nitrites so that they are
consistently below that level. The following treatment methods
have been approved by EPA for removing nitrates/nitrites: Ion
exchange, Reverse Osmosis, Electrodialysis. |
