Mammoth Hot Springs Water Quality Report

Annual Drinking Water Quality Report for 2023

Mammoth Hot Springs — Yellowstone National Park — Public Water System 5680092

We’re very pleased to provide you with this year's water quality report. Our goal is, and always has been, to provide a safe and dependable supply of drinking water. The data in this report span the entirety of calendar year 2023.

We want our residents, employees, and visitors to be informed about their water utility. If you have any questions about your water or this report, please contact Utility Systems Operations Facility Manager Jason Murphy or the Mammoth water treatment plant at 307-344-2353.

For a list of detected contaminants, please see Table 1. To view a comprehensive list of constituents for which we test, their definitions and effects, please see the Constituents Tested table below.

Usage and Production

Mammoth Hot Springs serves 300 year-round residents and 3,000 daily visitors during the peak summer season. In 2023, the Mammoth treatment plant produced a total of 112.4 million gallons of drinking water.

Source Water

Our source water is a combination of Indian and Panther Creeks. In addition, the Gardiner River is included during low flow conditions, typically in winter. A source water assessment was conducted in 2004. Findings from this study indicate that the greatest threat to the Mammoth water source is due to wildfires. A copy of this study is available at the Mammoth water treatment plant.

The sources of drinking water (both tap water and bottled water) include rivers, lakes, streams, ponds, reservoirs, springs, and wells. As water travels over the land or underground, it can pick up substances or contaminants such as microbes, inorganic and organic chemicals, and radioactive substances.

All drinking water, including bottled drinking water, may be reasonably expected to contain at least small amounts of some constituents. It's important to remember that the presence of these constituents does not necessarily pose a health risk. More information about contaminants and potential health effects can be obtained by calling the EPA’s Safe Drinking Water Hotline [phone]).

Contaminants that may be present in source water:

Microbial Contaminants, such as viruses and bacteria, which may come from sewage treatment plants, septic systems, agricultural livestock operations, and wildlife.

Pesticides and Herbicides, which may come from a variety of sources such as agriculture, urban storm water runoff, and residential uses.

Inorganic Contaminants, such as salts and metals, which can be naturally occurring or result from urban storm water runoff, industrial, or domestic wastewater discharges, oil and gas production, mining, or farming.

Organic Chemical Contaminants, including synthetic and volatile organic chemicals, which are by-products of industrial processes and petroleum production, and can, also, come from gas stations, urban storm water runoff, and septic systems.

Radioactive Contaminants, which can be naturally-occurring or be the result of oil and gas production and mining activities.

Treatment

Our raw water is treated with coagulants that serve to join together unwanted particles and make them easier to remove. We use a proprietary coagulant known as Aquahawk 107H, manufactured by Hawkins, Inc. This compound has been approved for drinking water use by NSF International, formerly the National Sanitation Foundation. Potassium permanganate, an inorganic salt and oxidant also common in the field of water treatment, is added to help remove organic material that may contribute to taste and odor issues.

The water is filtered through anthracite coal, silica sand, and garnet sand, to which the undesired particles adsorb. The final phase of the treatment process is the addition of a 12.5% solution of the disinfectant sodium hypochlorite (commonly known as liquid chlorine), which inactivates bacteria, viruses, and other microbes.

These processes are operated by a team of trained water and wastewater professionals certified by the state of Wyoming. We are assisted by supervisory control and data acquisition systems (SCADA), as well as a variety of National Park Service personnel.

Monitoring

The Mammoth Water Quality Laboratory and Energy Laboratories in Billings, Montana provide water testing services and support our quality assurance program. These certified laboratories follow precise drinking water analyses established by the U.S. Environmental Protection Agency and serve to ensure that our treated water meets federal regulations.

In order to ensure your tap water is safe, the Environmental Protection Agency has set very stringent levels or Maximum Contaminant Levels (MCLs) - the highest allowable level a contaminant is allowed in drinking water. A person would have to drink 2 liters of water every day at the MCL level for a lifetime to have a one-in-a-million chance of having the described health effect.

Some people may be more vulnerable to contaminants in drinking water than the general population. Immune-compromised persons such as persons with cancer undergoing chemotherapy, persons who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly, and infants can be particularly at risk from infections. These people should seek advice about drinking water from their health care providers. EPA/CDC guidelines on appropriate means to lessen the risk of infection by cryptosporidium and other microbiological contaminants are available from the Safe Drinking Water Hotline [phone]).

Sampling Frequency

Routine sampling and testing is an important part of our water quality and assurance program and includes the following:
Daily: Free Chlorine Residuals, Turbidity, pH, and Temperature.
Quarterly: Total Organic Carbon and Alkalinity.
Annually: Lead and Copper, Disinfection Byproducts (trihalomethanes, haloacetic acids), Volatile Organic Chemicals, Inorganics (metals), and Nitrates.
Every 3 Years: Synthetic Organic Chemicals.
Every 6 years: Radionuclides.

Definitions

The following terms and abbreviations have been defined, to help you better understand some terms you may not be familiar with:

AL—Action Level—The concentration of a contaminant which, if exceeded, triggers treatment or other requirements a water system must follow.

MCL—Maximum Contaminant Level —The “Maximum Allowed” is the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to the MCLGs as feasible using the best available treatment technology.

MCLG—Maximum Contaminant Level Goal—The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety.

NTU—Nephelometric Turbidity Unit—A measure of water clarity. Turbidity in excess of 5 NTU is just barely noticeable to the average person.

ND—Non-Detectable—Laboratory analysis indicates constituent is not present.

piCi/L—Picocuries per liter—A measure of radioactivity in water.

mg/l—Milligrams per liter—One part per million corresponds to one minute in two years or a single penny in $10,000. Same as ppm.

ppb—Parts per billion—One part per billion corresponds to one minute in two thousand years or a single penny in $10,000,000. Same as µg/L.

μg/L—Micrograms per liter—Same as ppb.

RAA—Running Annual Average—A year’s average, calculated by determining the monitoring periods that began within the past 365 days and averaging the result of the periods. As newer results are introduced into the calculation, older ones are removed.

SMCL - Secondary Maximum Contaminant Level - EPA does not enforce these levels. They are established as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color, and odor. These contaminants are not considered to present a risk to human health at the SMCL

TT—Treatment Technique—A required process intended to reduce the level of a contaminant in drinking water

Violations

Mammoth Hot Springs had one minor violation of routine reporting of chlorine for the surface water treatment rule in 2023 with a low value of chlorine on 8/28/23. A chlorine pump malfunctioned, resulting in non-delivery of NaOCl solution for a period of 1-2 hours. During this time the residual free chlorine level briefly dropped below 0.2 mg/L. The pump was replaced immediately and NaOCl delivery restored within 2 hours of the pump failure. Testing for free residual chlorine in the distribution system was performed at points immediately downstream of the entry to the distribution system and all were found to be above 0.2 mg/L.

Detections

We have learned through our monitoring and testing that some constituents have been detected. The EPA has determined that your water is safe at these levels. We are proud that your drinking water meets or exceeds all Federal and State requirements.

Table 1 lists those substances that were detected during the monitoring period of January 1, 2023 to December 31, 2023, or at the most recent sampling frequency.

For an entire list of tested constituents, their definitions and effects, please see the Constituents Tested table. below.

TEST RESULTS (Table 1)
Microorganisms
Contaminant	Violation Y/N	Sample Date	Highest Level Detected	Unit Measurement Detected	MCLG	MCL	Likely Source of Contamination
Turbidity	N	11/9/23	0.36	NTU	NO MCLG*	1.0 NTU	Soil runoff. *Although no goal for it exists, turbidity is an indicator of treatment plant performance. Its presence typically correlates with contaminants such as giardia.
						95% of samples ≤ 0.30 NTUs
Inorganic Contaminants
Contaminant	Violation Y/N	Sample Date	Highest Level Detected	Unit Measurement Detected	MCLG	MCL	Likely Source of Contamination
Barium	N	1/5/23	0.06	ppm	2.0	2.0	Weathering of rocks and soils containing barium.
Fluoride	N	1/5/23	0.10	ppm	4.0	4.0	Weathering of rocks and soils containing fluoride.
Nitrogen	N	1/5/23	0.15	ppm	10	10	Runoff from fertilizer use; leaking from septic tanks, sewage; erosion of natural deposits.
Sodium	N	1/5/23	3	ppm	NO MCLG*	NO MCL*	Erosion of natural deposits. *At the present time the EPA guidance level for sodium in drinking water is 20 mg/L. This value was developed for those individuals restricted to a total sodium intake of 500 mg/day.
Sulfate	N	1/5/23	23	ppm	NO MCLG*	NO MCL*	Weathering of rocks and soils containing sulfates. *Sulfate SMCL is 250 ppm.
Lead and Copper
Contaminant	Violation Y/N	Sample Dates	Highest Level Detected	Unit measurement Detected	MCLG	MCL	Likely Source of Contamination
Lead	N	9/13/23	90% = 0.001	ppm	0	AL = 0.015 ppm	Corrosion of household plumbing, erosion of natural deposits.
Copper	N	9/13/23	90% = 0.2225	ppm	0	AL = 1.3 ppm	Corrosion of household plumbing, erosion of natural deposits; leaching from wood preservatives.
If present, elevated levels of lead can cause serious health problems, especially for pregnant women and young children. Lead in drinking water is primarily from materials and components associated with service lines and home plumbing. The Mammoth Hot Springs water system is responsible for providing high quality drinking water, but cannot control the variety of materials used in plumbing components. When your water has been sitting for several hours, you can minimize the potential for lead exposure by flushing your tap for 30 seconds to 2 minutes before using for drinking or cooking. If you are concerned about lead in your water, you may wish to have your water tested. Information on lead in drinking water, testing methods, and steps you can take to minimize exposure is available from the Safe Drinking Water Hotline or at http://www.epa.gov/safewater/lead.
Disinfectant Byproducts
Contaminant	Violation Y/N	Sample Date	Highest Level Detected	Unit Measurement Detected	MCLG	MCL	Likely Source of Contamination
Bromo-dichloromethane (TTHM)	N	5/24/23	1.8	ppb	0	n/a	By-product of drinking water chlorination.
Chloroform (TTHM)	N	5/24/23	63	ppb	70	n/a	By-product of drinking water chlorination.
Total Trihalomethanes (TTHM)	N	5/24/23	65	ppb	n/a	80	By-product of drinking water chlorination.
Dibromoacetic acid (HAA5)	N	5/24/23	ND	ppb	n/a	n/a	By-product of drinking water chlorination.
Dichloroacetic acid (HAA5)	N	5/24/23	3.5	ppb	0	n/a	By-product of drinking water chlorination.
Monobromoacetic acid	N	5/24/23	ND	ppb	70	n/a	By-product of drinking water chlorination.
Monochloroacetic acid (HAA5)	N	5/24/23	ND	ppb	70	n/a	By-product of drinking water chlorination.
Tri-chloroacetic acid (HAA5)	N	5/24/23	24	ppb	20	n/a	By-product of drinking water chlorination.
Total Haloacetic Acids (HAA5)	N	5/24/23	28	ppb	n/a	60	By-product of drinking water chlorination.
Radioactive Contaminants
Contaminant	Violation Y/N	Sample Date	Highest Level Detected	Unit Measurement Detected	MCLG	MCL	Likely Source of Contamination
Gross Alpha	N	1/22/19	5.4 +/- 1.5	pCi/L	0	15	Erosion of natural deposits.
Total Organic Carbon
Contaminant	Violation Y/N	Sample Date	Removal ration	Unit Measurement	MCLG	MCL	Likely Source of Contamination
Total Organic Carbon (TOC)	N	quarterly	1.17	RAA removal ratio formula dependent on source water alkalinity and TOC, and/or treated water TOC and DBP levels.	n/a, TT	> 1.0 removal ratio	Decomposition of organic matter such as plants, animals, and microorganisms.

 

CONSTITUENTS TESTED Table 2
Contaminant	Violation Y/N	Level Detected	Unit Measurement	MCLG	MCL	Likely Source of Contamination
Microbiological Contaminants
1. Total Coliform Bacteria				0	presence of coliform bacteria in 5% of monthly samples	Naturally present in the environment.
2. Fecal coliform and E.coli				0	a routine sample and repeat sample are total coliform positive, and one is also fecal coliform or E. coli positive	Human and animal fecal waste.
3. Turbidity				n/a	TT	Soil runoff.
Radioactive Contaminants
4. Beta/photon emitters			mrem/yr	0	4	Decay of natural and man-made deposits.
5. Alpha emitters			pCI/L	0	15	Erosion of natural deposits.
6. Combined radium			pCI/L	0	5	Erosion of natural deposits.
Inorganic Contaminants
7. Antimony			ppb	6	6	Discharge from petroleum refineries; fire retardants; ceramics; electronics; solder.
8. Arsenic			ppb	n/a	10	Erosion of natural deposits; runoff from orchards; runoff from glass and electronics. production wastes
9. Asbestos			MFL	7	7	Decay of asbestos cement water mains; erosion of natural deposits.
10. Barium			ppm	2	2	Discharge of drilling wastes; discharge from metal refineries; erosion of natural deposits.
11. Beryllium			ppb	4	4	Discharge from metal refineries and coal-burning factories; discharge from electrical, aerospace, and defense industries.
12. Cadmium			ppb	5	5	Corrosion of galvanized pipes; erosion of natural deposits; discharge from metal refineries; runoff from waste batteries and paints.
13. Chromium			ppb	100	100	Discharge from steel and pulp mills; erosion of natural deposits.
14. Copper			ppm	1.3	AL=1.3	Corrosion of household plumbing systems; erosion of natural deposits; leaching from wood preservatives.
15. Cyanide			ppb	200	200	Discharge from steel/metal factories; discharge from plastic and fertilizer factories.
16. Fluoride			ppm	4	4	Erosion of natural deposits; water additive which promotes strong teeth; discharge from fertilizer and aluminum factories.
17. Lead			ppb	0	AL=15	Corrosion of household plumbing systems, erosion of natural deposits.
18. Mercury (inorganic)			ppb	2	2	Erosion of natural deposits; discharge from refineries and factories; runoff from landfills; runoff from cropland.
19. Nitrate (as Nitrogen)			ppm	10	10	Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits.
20. Nitrite (as Nitrogen)			ppm	1	1	Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits.
21. Selenium			ppb	50	50	Discharge from petroleum and metal refineries; erosion of natural deposits; discharge from mines.
22. Thallium			ppb	0.5	2	Leaching from ore-processing sites; discharge from electronics, glass, and drug factories.
Synthetic Organic Contaminants including Pesticides and Herbicides
23. 2,4-D			ppb	70	70	Runoff from herbicide used on row crops.
24. 2,4,5-TP (Silvex)			ppb	50	50	Residue of banned herbicide.
25. Acrylamide				0	TT	Added to water during sewage/wastewater treatment.
26. Alachlor			ppb	0	2	Runoff from herbicide used on row crops.
27. Atrazine			ppb	3	3	Runoff from herbicide used on row crops.
28. Benzo(a)pyrene (PAH)			ng/L	0	200	Leaching from linings of water storage tanks and distribution lines.
29. Carbofuran			ppb	40	40	Leaching of soil fumigant used on rice and alfalfa.
30. Chlordane			ppb	0	2	Residue of banned termiticide.
31. Dalapon			ppb	200	200	Runoff from herbicide used on rights of way.
32. Di(2-ethylhexyl) adipate			ppb	400	400	Discharge from chemical factories.
33. Di(2-ethylhexyl) phthalate			ppb	0	6	Discharge from rubber and chemical factories.
34. Dibromochloropropane			ng/L	0	200	Runoff/leaching from soil fumigant used on soybeans, cotton, pineapples, and orchards.
35. Dinoseb			ppb	7	7	Runoff from herbicide used on soybeans and vegetables.
36. Diquat			ppb	20	20	Runoff from herbicide use.
37. Dioxin [2,3,7,8-TCDD]			pg/L	0	30	Emissions from waste incineration and other combustion; discharge from chemical factories.
38. Endothall			ppb	100	100	Runoff from herbicide use.
39. Endrin			ppb	2	2	Residue of banned insecticide.
40. Epichlorohydrin				0	TT	Discharge from industrial chemical factories; an impurity of some water treatment chemicals.
41. Ethylene dibromide			ng/L	0	50	Discharge from petroleum refineries.
42. Glyphosate			ppb	700	700	Runoff from herbicide use.
43. Heptachlor			ng/L	0	400	Residue of banned termiticide.
44. Heptachlor epoxide			ng/L	0	200	Breakdown of heptachlor.
45. Hexachlorobenzene			ppb	0	1	Discharge from metal refineries and agricultural chemical factories.
46. Hexachlorocyclo- pentadiene			ppb	50	50	Discharge from chemical factories.
47. Lindane			ng/L	200	200	Runoff/leaching from insecticide used on cattle, lumber, gardens.
48. Methoxychlor			ppb	40	40	Runoff/leaching from insecticide used on fruits, vegetables, alfalfa, livestock.
49. Oxamyl [Vydate]			ppb	200	200	Runoff/leaching from insecticide used on apples, potatoes and tomatoes.
50. PCBs [Polychlorinated biphenyls]			ng/L	0	500	Runoff from landfills; discharge of waste chemicals.
51. Pentachlorophenol			ppb	0	1	Discharge from wood preserving factories.
52. Picloram			ppb	500	500	Herbicide runoff.
53. Simazine			ppb	4	4	Herbicide runoff.
54. Toxaphene			ppb	0	3	Runoff/leaching from insecticide used on cotton and cattle.
Volatile Organic Contaminants
55. Benzene			ppb	0	5	Discharge from factories; leaching from gas storage tanks and landfills.
56. Carbon tetrachloride			ppb	0	5	Discharge from chemical plants and other industrial activities.
57. Chlorobenzene			ppb	100	100	Discharge from chemical and agricultural chemical factories.
58. o-Dichlorobenzene			ppb	600	600	Discharge from industrial chemical factories.
59. p-Dichlorobenzene			ppb	75	75	Discharge from industrial chemical factories.
60. 1,2 - Dichloroethane			ppb	0	5	Discharge from industrial chemical factories.
61. 1,1 - Dichloroethylene			ppb	7	7	Discharge from industrial chemical factories.
62. cis-1,2-ichloroethylene			ppb	70	70	Discharge from industrial chemical factories.
63. trans - 1,2 -Dichloroethylene			ppb	100	100	Discharge from industrial chemical factories.
64. Dichloromethane			ppb	0	5	Discharge from pharmaceutical and chemical factories.
65. 1,2-Dichloropropane			ppb	0	5	Discharge from industrial chemical factories.
66. Ethylbenzene			ppb	700	700	Discharge from petroleum refineries.
67. Styrene			ppb	100	100	Discharge from rubber and plastic factories; leaching from landfills.
68. Tetrachloroethylene			ppb	0	5	Leaching from PVC pipes; discharge from factories and dry cleaners.
69. 1,2,4 -Trichlorobenzene			ppb	70	70	Discharge from textile-finishing factories
70. 1,1,1 - Trichloroethane			ppb	200	200	Discharge from metal degreasing sites and other factories
71. 1,1,2 -Trichloroethane			ppb	3	5	Discharge from industrial chemical factories
72. Trichloroethylene			ppb	0	5	Discharge from metal degreasing sites and other factories
73. TTHM [Total trihalomethanes]			ppb	0	100	By-product of drinking water chlorination
74. Toluene			ppm	1	1	Discharge from petroleum factories
75. Vinyl Chloride			ppb	0	2	Leaching from PVC piping; discharge from plastics factories
76. Xylenes			ppm	10	10	Discharge from petroleum factories; discharge from chemical factories.

Microbiological Contaminants:
(1) Total Coliform. Coliforms are bacteria that are naturally present in the environment and are used as an indicator that other, potentially-harmful, bacteria may be present. Coliforms were found in more samples than allowed and this was a warning of potential problems.
(2) Fecal coliform/E.Coli. Fecal coliforms 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. They may pose a special health risk for infants, young children, and people with severely compromised immune systems.
(3) Turbidity. 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.

Radioactive Contaminants:

(4) 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 the MCL over many years may have an increased risk of getting cancer.
(5) 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 the MCL over many years may have an increased risk of getting cancer.
(6) Combined Radium 226/228. Some people who drink water containing radium 226 or 228 in excess of the MCL over many years may have an increased risk of getting cancer.

Inorganic Contaminants:

(7) Antimony. Some people who drink water containing antimony well in excess of the MCL over many years could experience increases in blood cholesterol and decreases in blood sugar.
(8) Arsenic. Some people who drink water containing arsenic in excess of the MCL over many years could experience skin damage or problems with their circulatory system, and may have an increased risk of getting cancer.
(9) Asbestos. Some people who drink water containing asbestos in excess of the MCL over many years may have an increased risk of developing benign intestinal polyps.
(10) Barium. Some people who drink water containing barium in excess of the MCL over many years could experience an increase in their blood pressure.
(11) Beryllium. Some people who drink water containing beryllium well in excess of the MCL over many years could develop intestinal lesions.
(12) Cadmium. Some people who drink water containing cadmium in excess of the MCL over many years could experience kidney damage.
(13) Chromium. Some people who use water containing chromium well in excess of the MCL over many years could experience allergic dermatitis.
(14) Copper. Copper is an essential nutrient, but some people who drink water containing copper in excess of the action level over a relatively short amount of time could experience gastrointestinal distress. Some people who drink water containing copper in excess of the action level over many years could suffer liver or kidney damage. People with Wilson's Disease should consult their personal doctor.
(15) Cyanide. Some people who drink water containing cyanide well in excess of the MCL over many years could experience nerve damage or problems with their thyroid.
(16) Fluoride. Some people who drink water containing fluoride in excess of the MCL over many years could get bone disease, including pain and tenderness of the bones. Children may get mottled teeth.
(17) Lead. Infants and children who drink water containing lead in excess of the action level could experience delays in their physical or mental development. Children could show slight deficits in attention span and learning abilities. Adults who drink this water over many years could develop kidney problems or high blood pressure.
(18) Mercury (inorganic). Some people who drink water containing inorganic mercury well in excess of the MCL over many years could experience kidney damage.
(19) Nitrate. Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome.
(20) Nitrite. Infants below the age of six months who drink water containing nitrite in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome.
(21) Selenium. Selenium is an essential nutrient. However, some people who drink water containing selenium in excess of the MCL over many years could experience hair or fingernail losses, numbness in fingers or toes, or problems with their circulation.
(22) Thallium. Some people who drink water containing thallium in excess of the MCL over many years could experience hair loss, changes in their blood, or problems with their kidneys, intestines, or liver.

Synthetic organic contaminants including pesticides and herbicides:

(23) 2,4-D. Some people who drink water containing the weed killer 2,4-D well in excess of the MCL over many years could experience problems with their kidneys, liver, or adrenal glands.
(24) 2,4,5-TP (Silvex). Some people who drink water containing silvex in excess of the MCL over many years could experience liver problems.
(25) Acrylamide. Some people who drink water containing high levels of acrylamide over a long period of time could have problems with their nervous system or blood, and may have an increased risk of getting cancer.
(26) Alachlor. Some people who drink water containing alachlor in excess of the MCL over many years could have problems with their eyes, liver, kidneys, or spleen, or experience anemia, and may have an increased risk of getting cancer.
(27) Atrazine. Some people who drink water containing atrazine well in excess of the MCL over many years could experience problems with their cardiovascular system or reproductive difficulties.
(28) Benzo(a)pyrene [PAH]. Some people who drink water containing benzo(a)pyrene in excess of the MCL over many years may experience reproductive difficulties and may have an increased risk of getting cancer.
(29) Carbofuran. Some people who drink water containing carbofuran in excess of the MCL over many years could experience problems with their blood, or nervous or reproductive systems.
(30) Chlordane. Some people who drink water containing chlordane in excess of the MCL over many years could experience problems with their liver or nervous system, and may have an increased risk of getting cancer.
(31) Dalapon. Some people who drink water containing dalapon well in excess of the MCL over many years could experience minor kidney changes.
(32) Di (2-ethylhexyl) adipate. Some people who drink water containing di (2-ethylhexyl) adipate well in excess of the MCL over many years could experience general toxic effects or reproductive difficulties.
(33) Di (2-ethylhexyl) phthalate. Some people who drink water containing di (2-ethylhexyl) phthalate in excess of the MCL over many years may have problems with their liver, or experience reproductive difficulties, and may have an increased risk of getting cancer.
(34) Dibromochloropropane (DBCP). Some people who drink water containing DBCP in excess of the MCL over many years could experience reproductive difficulties and may have an increased risk of getting cancer.
(35) Dinoseb. Some people who drink water containing dinoseb well in excess of the MCL over many years could experience reproductive difficulties.
(36) Dioxin (2,3,7,8-TCDD). Some people who drink water containing dioxin in excess of the MCL over many years could experience reproductive difficulties and may have an increased risk of getting cancer.
(37) Diquat. Some people who drink water containing diquat in excess of the MCL over many years could get cataracts.
(38) Endothall. Some people who drink water containing endothall in excess of the MCL over many years could experience problems with their stomach or intestines.
(39) Endrin. Some people who drink water containing endrin in excess of the MCL over many years could experience liver problems.
(40) Epichlorohydrin. Some people who drink water containing high levels of epichlorohydrin over a long period of time could experience stomach problems, and may have an increased risk of getting cancer.
(41) Ethylene dibromide. Some people who drink water containing ethylene dibromide in excess of the MCL over many years could experience problems with their liver, stomach, reproductive system, or kidneys, and may have an increased risk of getting cancer.
(42) Glyphosate. Some people who drink water containing glyphosate in excess of the MCL over many years could experience problems with their kidneys or reproductive difficulties.
(43) Heptachlor. Some people who drink water containing heptachlor in excess of the MCL over many years could experience liver damage and may have an increased risk of getting cancer.
(44) Heptachlor epoxide. Some people who drink water containing heptachlor epoxide in excess of the MCL over many years could experience liver damage, and may have an increased risk of getting cancer.
(45) Hexachlorobenzene. Some people who drink water containing hexachlorobenzene in excess of the MCL over many years could experience problems with their liver or kidneys, or adverse reproductive effects, and may have an increased risk of getting cancer.
(46) Hexachlorocyclopentadiene. Some people who drink water containing hexachlorocyclopentadiene well in excess of the MCL over many years could experience problems with their kidneys or stomach.
(47) Lindane. Some people who drink water containing lindane in excess of the MCL over many years could experience problems with their kidneys or liver.
(48) Methoxychlor. Some people who drink water containing methoxychlor in excess of the MCL over many years could experience reproductive difficulties.
(49) Oxamyl [Vydate]. Some people who drink water containing oxamyl in excess of the MCL over many years could experience slight nervous system effects.
(50) PCBs [Polychlorinated biphenyls]. Some people who drink water containing PCBs in excess of the MCL over many years could experience changes in their skin, problems with their thymus gland, immune deficiencies, or reproductive or nervous system difficulties, and may have an increased risk of getting cancer.
(51) Pentachlorophenol. Some people who drink water containing pentachlorophenol in excess of the MCL over many years could experience problems with their liver or kidneys, and may have an increased risk of getting cancer.
(52) Picloram. Some people who drink water containing picloram in excess of the MCL over many years could experience problems with their liver.
(53) Simazine. Some people who drink water containing simazine in excess of the MCL over many years could experience problems with their blood.
(54) Toxaphene. Some people who drink water containing toxaphene in excess of the MCL over many years could have problems with their kidneys, liver, or thyroid, and may have an increased risk of getting cancer.

Volatile Organic Contaminants:

(55) Benzene. Some people who drink water containing benzene in excess of the MCL over many years could experience anemia or a decrease in blood platelets, and may have an increased risk of getting cancer.
(56) Carbon Tetrachloride. Some people who drink water containing carbon tetrachloride in excess of the MCL over many years could experience problems with their liver and may have an increased risk of getting cancer.
(57) Chlorobenzene. Some people who drink water containing chlorobenzene in excess of the MCL over many years could experience problems with their liver or kidneys.
(58) o-Dichlorobenzene. Some people who drink water containing o-dichlorobenzene well in excess of the MCL over many years could experience problems with their liver, kidneys, or circulatory systems.
(59) p-Dichlorobenzene. Some people who drink water containing p-dichlorobenzene in excess of the MCL over many years could experience anemia, damage to their liver, kidneys, or spleen, or changes in their blood.
(60) 1,2-Dichloroethane. Some people who drink water containing 1,2-dichloroethane in excess of the MCL over many years may have an increased risk of getting cancer.
(61) 1,1-Dichloroethylene. Some people who drink water containing 1,1-dichloroethylene in excess of the MCL over many years could experience problems with their liver.
(62) cis-1,2-Dichloroethylene. Some people who drink water containing cis-1,2-dichloroethylene in excess of the MCL over many years could experience problems with their liver.
(63) trans-1,2-Dicholoroethylene. Some people who drink water containing trans-1,2-dichloroethylene well in excess of the MCL over many years could experience problems with their liver.
(64) Dichloromethane. Some people who drink water containing dichloromethane in excess of the MCL over many years could have liver problems and may have an increased risk of getting cancer.
(65) 1,2-Dichloropropane. Some people who drink water containing 1,2-dichloropropane in excess of the MCL over many years may have an increased risk of getting cancer.
(66) Ethylbenzene. Some people who drink water containing ethylbenzene well in excess of the MCL over many years could experience problems with their liver or kidneys.
(67) Styrene. Some people who drink water containing styrene well in excess of the MCL over many years could have problems with their liver, kidneys, or circulatory system.
(68) Tetrachloroethylene. Some people who drink water containing tetrachloroethylene in excess of the MCL over many years could have problems with their liver, and may have an increased risk of getting cancer.
(69) 1,2,4-Trichlorobenzene. Some people who drink water containing 1,2,4-trichlorobenzene well in excess of the MCL over many years could experience changes in their adrenal glands.
(70) 1,1,1,-Trichloroethane. Some people who drink water containing 1,1,1-trichloroethane in excess of the MCL over many years could experience problems with their liver, nervous system, or circulatory system.
(71) 1,1,2-Trichloroethane. Some people who drink water containing 1,1,2-trichloroethane well in excess of the MCL over many years could have problems with their liver, kidneys, or immune systems.
(72) Trichloroethylene. Some people who drink water containing trichloroethylene in excess of the MCL over many years could experience problems with their liver and may have an increased risk of getting cancer.
(73) TTHMs [Total Trihalomethanes]. Some people who drink water containing trihalomethanes in excess of the MCL over many years may experience problems with their liver, kidneys, or central nervous systems, and may have an increased risk of getting cancer.
(74) Toluene. Some people who drink water containing toluene well in excess of the MCL over many years could have problems with their nervous system, kidneys, or liver.
(75) Vinyl Chloride. Some people who drink water containing vinyl chloride in excess of the MCL over many years may have an increased risk of getting cancer.
(76) Xylenes. Some people who drink water containing xylenes in excess of the MCL over many years could experience damage to their nervous system.