Nitrate & Nitrite Levels in Water & Food: Human Exposure & Health Risks | Study Guides, Projects, Research Nutrition

177 NITRATE AND NITRITE

6. POTENTIAL FOR HUMAN EXPOSURE

6.1 OVERVIEW

Nitrate and nitrite are ubiquitous in the environment. Specific salts have occasionally been identified in

hazardous waste sites. Ammonium nitrate, sodium nitrate, and sodium nitrite were identified in 7, 3, and

2, of the 1,832 hazardous waste sites, respectively that have been proposed for inclusion on the EPA

National Priorities List (NPL) (ATSDR 2015). However, the number of sites evaluated for these

substances is not known. The frequency of these sites can be seen in Figures 6-1, 6-2, and 6-3.

Nitrate may enter the environment via natural and anthropogenic sources. Nitrate and nitrite occur

naturally in the environments as a part of the earth’s nitrogen cycle. A major source of anthropogenic

nitrate and nitrite is artificial fertilizers, and various industrial processes also produce nitrate in their waste

streams (Environment Canada 2012; WHO 1978). Inorganic fertilizer and nitrification of animal waste

are the principal sources of nitrate in the environment (Environment Canada 2012; Nolan et al. 1997).

However, contributions from human waste must be taken into account as well. Point and non-point

anthropogenic sources that contribute include industrial waste water, mining (explosives) waste water,

agricultural and urban runoff, feedlot discharges, septic system and landfill leachate, lawn fertilizers,

storm sewer overflow, and nitric oxide and nitrogen dioxide from vehicle exhaust (Environment Canada

2012). Additionally, organic forms of nitrogen in the environment from various sources may undergo

ammonification to form inorganic ammonia and ammonium, and nitrification to form nitrate, and have the

potential to be released into surface waters (Environment Canada 2012). Inorganic nitrate and nitrite in

soil and water can be taken up by plants used for human consumption (ATSDR 2013a).

Exposure from drinking water of private wells is a source of concern as elevated concentrations have been

reported in some wells, yet these water sources are not routinely tested, monitored, or regulated since they

are not covered by the Safe Drinking Water Act (SDWA). About 15% of Americans use private wells as

a source of drinking water and an important percentage of them may have a septic system serving their

homes. Additionally, nitrate and nitrite exposure can occur from the ingestion of foods containing high

levels of these chemicals (ATSDR 2013a).

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6. POTENTIAL FOR HUMAN EXPOSURE

6.1 OVERVIEW

Nitrate and nitrite are ubiquitous in the environment. Specific salts have occasionally been identified in

hazardous waste sites. Ammonium nitrate, sodium nitrate, and sodium nitrite were identified in 7, 3, and

2, of the 1,832 hazardous waste sites, respectively that have been proposed for inclusion on the EPA

National Priorities List (NPL) (ATSDR 2015). However, the number of sites evaluated for these

substances is not known. The frequency of these sites can be seen in Figures 6-1, 6-2, and 6-3.

Nitrate may enter the environment via natural and anthropogenic sources. Nitrate and nitrite occur

naturally in the environments as a part of the earth’s nitrogen cycle. A major source of anthropogenic

nitrate and nitrite is artificial fertilizers, and various industrial processes also produce nitrate in their waste

streams (Environment Canada 2012; WHO 1978). Inorganic fertilizer and nitrification of animal waste

are the principal sources of nitrate in the environment (Environment Canada 2012; Nolan et al. 1997).

However, contributions from human waste must be taken into account as well. Point and non-point

anthropogenic sources that contribute include industrial waste water, mining (explosives) waste water,

agricultural and urban runoff, feedlot discharges, septic system and landfill leachate, lawn fertilizers,

storm sewer overflow, and nitric oxide and nitrogen dioxide from vehicle exhaust (Environment Canada

2012). Additionally, organic forms of nitrogen in the environment from various sources may undergo

ammonification to form inorganic ammonia and ammonium, and nitrification to form nitrate, and have the

potential to be released into surface waters (Environment Canada 2012). Inorganic nitrate and nitrite in

soil and water can be taken up by plants used for human consumption (ATSDR 2013a).

Exposure from drinking water of private wells is a source of concern as elevated concentrations have been

reported in some wells, yet these water sources are not routinely tested, monitored, or regulated since they

are not covered by the Safe Drinking Water Act (SDWA). About 15% of Americans use private wells as

a source of drinking water and an important percentage of them may have a septic system serving their

homes. Additionally, nitrate and nitrite exposure can occur from the ingestion of foods containing high

levels of these chemicals (ATSDR 2013a).

Figure 6-1. Frequency of NPL Sites with Ammonium Nitrate Contamination

Figure 6-3. Frequency of NPL Sites with Sodium Nitrite Contamination

6.2 RELEASES TO THE ENVIRONMENT

The Toxics Release Inventory (TRI) data should be used with caution because only certain types of

facilities are required to report (EPA 2005). This is not an exhaustive list. Manufacturing and processing

facilities are required to report information to the TRI only if they employ 10 or more full-time

employees; if their facility is included in Standard Industrial Classification (SIC) Codes 10 (except 1011,

1081, and 1094), 12 (except 1241), 20–39, 4911 (limited to facilities that combust coal and/or oil for the

purpose of generating electricity for distribution in commerce), 4931 (limited to facilities that combust

coal and/or oil for the purpose of generating electricity for distribution in commerce), 4939 (limited to

facilities that combust coal and/or oil for the purpose of generating electricity for distribution in

commerce), 4953 (limited to facilities regulated under RCRA Subtitle C, 42 U.S.C. section 6921 et seq.),

5169, 5171, and 7389 (limited S.C. section 6921 et seq.), 5169, 5171, and 7389 (limited to facilities

primarily engaged in solvents recovery services on a contract or fee basis); and if their facility produces,

imports, or processes ≥25,000 pounds of any TRI chemical or otherwise uses >10,000 pounds of a TRI

chemical in a calendar year (EPA 2005).

Nitrate is released into the environment through both natural and anthropogenic sources. Naturally

occurring nitrate and nitrite are part of the earth’s nitrogen cycle. Anthropogenic sources, including

animal and human organic wastes as well as nitrogen-containing fertilizers, increase the concentrations of

nitrate in the environment. Nitrate and nitrite are present in the environment, in soils and water, and to a

lesser extent, in air, plant materials, and meat products. Concentrations of nitrite in plants and water are

low relative to nitrate concentration due to the fact that nitrite is easily oxidized to nitrate (WHO 1978).

Nitrate is the ion detected in the majority of groundwater and surface water samples because the nitrite

ion is easily oxidized to nitrate in the environment; the nitrate ion is stable and is chemically unreactive

under most environmental conditions (IARC 2010; WHO 2011b).

6.2.1 Air

Estimated releases of 301,654 pounds (~137 metric tons) of nitrate compounds to the atmosphere from

2,110 domestic manufacturing and processing facilities in 2013, accounted for about 0.1% of the

estimated total environmental releases from facilities required to report to the TRI (TRI13 2014). These

releases are summarized in Table 6-1. Estimated releases of 65,201 (~30 metric tons) pounds of sodium

nitrite were released to the atmosphere from 363 domestic manufacturing and

Table 6-1. Releases to the Environment from Facilities that Produce, Process, or

Use Nitrate Compoundsa

Reported amounts released in pounds per yearb

Total release

On- and off-

Statec^ RF d^ Air e^ Water f^ UIg^ Land h^ Other i^ On-sitej^ Off-sitek^ site

PA 67 9,139 7,212,765 0 66,541 2,428 7,224,885 65,988 7,290,

PR 7 0 0 1,465 120 34 1,465 154 1,

RI 6 0 121 0 0 20,098 121 20,098 20,

SC 43 3,001 2,346,088 0 178,745 458 2,376,696 151,596 2,528,

SD 8 0 2,995,074 2,000 338,782 6 3,280,324 55,538 3,335,

TN 45 270 2,748,175 470,956 125,258 1,678 2,772,445 573,892 3,346,

TX 131 788 14,234,564 7,762,004 876,395 7,165 21,822,716 1,058,200 22,880,

UT 37 329 97,000 0 1,282,016 29 714,559 664,815 1,379,

VA 42 3,558 10,978,189 0 4,587 1 10,981,823 4,511 10,986,

VT 6 0 124,890 0 57,395 0 124,890 57,395 182,

WA 46 8,770 1,190,505 0 981,730 0 1,631,774 549,231 2,181,

WI 127 591 2,162,376 0 2,339,390 31,174 3,734,315 799,216 4,533,

WV 18 18,000 2,140,714 0 2,138 0 2,160,673 179 2,160,