Water and Health

In addition to conducting hundreds of thousands of water quality analyses of regulated contaminants for compliance monitoring and treatment process control, MWRA collects many other samples to understand more about our water, to track how the system is working and changing over time, and to help researchers and EPA regulators determine if new water quality standards are needed.

MWRA publishes an Annual Water Quality Report, focused primarily on regulated water quality parameters and a more detailed monthly report. More information on MWRA's key performance measures for water quality, maintenance, and financial management can be found here. Additionally to all the data regularly published in those reports, MWRA believes that our users should have access to the water quality data we collect on a periodic basis for other purposes.

Special Health Considerations: Important Information for People with Weakened Immune Systems

According to the Center for Disease Control (CDC), drinking water is not the primary pathway for infection by Giardia or Cryptosporidium.

Some people may be more vulnerable to contaminants in drinking water than the general population. Immuno-compromised persons such as persons with cancer undergoing chemotherapy, persons who have undergone organ transplants or dialysis, and people with HIV/AIDS or other immune system disorders can be at increased risk from protozoa. People who are immuno-compromised should seek advice from their health care providers to make the right decisions about water consumption.

Protozoa Monitoring Program

Giardia and Cryptosporidium are protozoa that are of significant concern in drinking water supplies, because they are the most difficult organisms to inactivate with disinfection. EPA’s Surface Water Treatment Rule sets inactivation requirements for Giardia, while the Long Term 2 Enhanced Surface Water Treatment Rule sets inactivation requirements for Cryptosporidium. MWRA meets all treatment requirements for inactivation of both Giardia and Cryptosporidium through use of ozone and UV disinfection.

Wachusett Reservoir raw water is sampled weekly at Carroll Water Treatment Plant (CWTP). The Quabbin Reservoir has biweekly raw water sampling which is conducted at Brutsch Water Treatment Facility. Giardia and Cryptosporidium results are reported as number of oocysts per 100 Litres (L).

Giardia and Cryptosporidium sampling were initiated in 1994. In mid-January 1999, sampling was increased to weekly at the Cosgrove Intake. Until March 2004, MWRA used the EPA-approved method, ASTM D19 (ICR) with 100 L samples. Under this method, identifications were grouped into 2 categories: presumed (no internal structures identified) and confirmed (1 or more internal structures identified). From July 1997 to March 2004, no samples confirmed positive for Giardia, and no samples were presumptive or confirmed positive for Cryptosporidium.

In April 2004, MWRA began testing samples using EPA-approved Method 1623 with 50 L samples, which is about twice as sensitive as ICR method – 3 to 4 times the recovery rate with half the volume. Under the new method, identifications are grouped into 3 categories: empty (no internal structures), amorphous structure (structure not consistent with a normal organism), and one or more internal structures.

Neither method listed above is capable of determining if cysts are alive or dead, or if they are capable of causing human infection. Even without knowledge of infectivity, MWRA has developed trigger levels for these organisms above which notification to Department of Public Health is made, and additional sampling and watershed review actions are undertaken:

For Cryptosporidium: Above 0.1 oocysts/L, or 10 oocysts/100 L
For Giardia: Above 0.3 cysts/L, or 30 cysts/100 L

At or below this level, no special actions are required.

A summary of these results is listed below.

Quabbin and Wachusett Reservoir Cryptosporidum and Giardia Test Results
2023 (PDF)
2022 (PDF)
2021 (PDF)
2020 (PDF)
2019 (PDF)
2017-2018 (PDF)
2016 (PDF)
2015 (PDF)
2009-2014 (PDF)
2004-2008 (PDF)
1997-2004 (PDF)
1998-2004 (PDF)

Annual Summaries of Cryptosporidum and Giardia Test Results at the Quabbin and Wachusett Reservoir 2003-2008
2008 Results (PDF)
2007 Results (PDF)
2006 Results (PDF)
2004 Results (PDF)
2003 Results (PDF)

For more information, please contact:

Beverly Anderson, MWRA Public Health Project Manager

Although data are not sufficient for EPA/CDC to recommend that all severely immuno-compromised persons take extra caution with regards to their drinking water, individuals who wish to take extra measures to avoid waterborne Cryptosporidiosis can bring their drinking water to a full boil for one minute. Boiling water is the most effective way of killing Cryptosporidium.

FOR PEOPLE WITH WEAKENED IMMUNE SYSTEMS OR WITH HIV/AIDS: EXTRA PRECAUTIONS TO AVOID CRYPTOSPORIDIOSIS & GIARDIASIS
If you are HIV positive or otherwise immuno-compromised, be extra careful about hand washing.
Carefully wash food before eating, and thoroughly cook foods which need heating before eating. Do not let raw foods contaminate other foods.
Avoid drinking or accidentally swallowing water from lakes, rivers, or swimming pools.
Follow "safe sex" guidelines. Any sex act that involves contact with the anus or feces increases the risk of cryptosporidiosis.
Drinking water that is considered safe for persons with healthy immune systems may not be healthy for those with weakened immunity. You may want to discuss the need for taking further protective measures with your medical provider.

A list of potential contaminants that are routinely tested for in the MWRA water system.

MWRA has tested for a wide variety of pesticides and herbicides in our source and treated water, including the controversial herbicide glyphosate. Due primarily to MWRA's well-protected watersheds, it is unlikely that they would be found, and both regular and special testing efforts have shown this to be true. Only one pesticide has ever been detected, and that result is considered uncertain.

Substance	Measurement Units	Average	Range
PBO - Piperonyl Butoxide	parts per billion (ppb)	0.0012	0 - 0.006
The State of Massachusetts sprayed for mosquito control in September 2019 in response to the elevated risk of Eastern Equine Encephalitis (EEE). The mosquitocide used was Anvil 10+10, composed of the pesticide Sumithrin (also known as d-Phenothrin) plus the synergist, piperonyl butoxide (also known as PBO). Water supplies identified by MassDEP as being in close proximity to the spraying were tested for the mosquitocide. EPA and MassDEP have a health guidance level of 992 ppb. Consumption of drinking water for many years above that level could result in effects on the liver and may possibly incdrese the risk of cancer. The state laboratory indicated that it had detected PBO in treated water from Wachusett Reservoir prior to spraying, but not in any samples of treated water after spraying. That result, if real, would have been more than 100,000 times lower that the health guidance level.

Substance

Measurement Units

Average

Range

PBO - Piperonyl Butoxide

parts per billion (ppb)

0.0012

0 - 0.006

The State of Massachusetts sprayed for mosquito control in September 2019 in response to the elevated risk of Eastern Equine Encephalitis (EEE). The mosquitocide used was Anvil 10+10, composed of the pesticide Sumithrin (also known as d-Phenothrin) plus the synergist, piperonyl butoxide (also known as PBO). Water supplies identified by MassDEP as being in close proximity to the spraying were tested for the mosquitocide. EPA and MassDEP have a health guidance level of 992 ppb. Consumption of drinking water for many years above that level could result in effects on the liver and may possibly incdrese the risk of cancer.

The state laboratory indicated that it had detected PBO in treated water from Wachusett Reservoir prior to spraying, but not in any samples of treated water after spraying. That result, if real, would have been more than 100,000 times lower that the health guidance level.

For more information, please contact:

Beverly Anderson, MWRA Public Health Project Manager

"Secondary contaminants" include substances that are not health related, but may cause aesthetic, cosmetic, or technical effects in drinking water. Aesthetic effects cause unfavorable tastes and odors, while cosmetic effects cause visual changes which do not damage the body, but are still undesirable. Technical effects cause damage to water equipment or reduced effectiveness of treatment for other contaminants. These contaminants can cause changes in water cloudiness, taste, odor, color, or skin and tooth discoloration at higher levels.

Secondary Maximum Contaminant Levels (SMCLs) are guideline values determined by EPA and MassDEP. They provide non-enforceable limits for public water systems for the management of drinking water, but are not considered a risk to human health at the level of the SMCL. MWRA monitors for these substances on a monthly or quarterly basis.

The tables below provide a summary of 2022 data. For current data on secondary contaminants in MWRA water, see the MWRA monthly water quality reports.

For more information on secondary contaminants, go to the EPA's Secondary Drinking Water Standards: Guidance for Nuisance Chemicals or the Massachusetts Drinking Water Standards and Guidelines

In the tables below, CVA is Chicopee Valley Aqueduct communities and Metro Boston is all Metro Boston and Metro West communities serviced by the Carroll Water Treatment Plant. See About MWRA for a list of which communities are served by each system. Values are for finished water after treatment unless otherwise indicated.

ND stands for “not detectable” in MWRA water ug/L is the equivalent of parts per billion and mg/L equals parts per million.

Aluminum
	Units	Average	Range
Metro Boston	ug/L	2.97	ND -19.1
CVA	ug/L	ND	ND
Aluminum is a naturally occurring metal that enters into our water system from rocks and soil. MWRA does not use any aluminum containing treatment chemicals. Elevated aluminum metals can cause water to turn a greyish color. The SMCL for aluminum is 200 ug/L. MWRA aluminum levels are well below the MassDEP guidelines.

pH
	Units	Average	Range
Metro Boston	S.U.	9.6	9.3 – 9.8
CVA	S.U.	7.2	6.8 – 7.6
pH is a measurement of the acidity of a substance. Levels below 7 represent acidity and levels above 7 represent alkalinity. At a lower pH, water will corrode metals such as lead, allowing them to leach into the water. The pH of source water can be changed by local runoff and leaching of natural deposits. The pH of treated water is altered by treatment processes to manage water quality. Depending on the pH, water can take on a different taste. Low pH may produce a bitter metallic taste and a high pH may produce a slippery feel or a soda like taste. The data in the table represent treated water within the distribution system. The MWRA adjusts the pH of Metro Boston drinking water to a pH of 9.0 to 9.5 within the distribution system to prevent corrosion and reduce the release of lead from service lines and home plumbing. While the pH is above the aesthetic guideline of 6.5 to 8.5, the values are necessary for the protection of public health. MWRA MetroBoston pH levels are those required to meet MassDEP requirements under the Lead and Copper Rule for optimum corrosion control of lead and copper. The values reported for the CVA system are for water delivered to each community. Each CVA community treats the water to reduce corrosion, and may have different pH values.

Chloride
	Units	Average	Range
Metro Boston	mg/L	30.8	23.1 – 40.0
CVA	mg/L	12.99	8.9 – 24.6
Chloride can enter drinking water from natural minerals or deposits or the use of sodium chloride (NaCl) for road deicing. At elevated levels, chloride can cause water to have a salty taste. The SMCL for chloride is 250 mg/L. MWRA chloride levels are well below the MassDEP guidelines.

Color
	Units	Average	Range
Metro Boston	C.U.	6.3	5 - 7
CVA	C.U.	4.8	4 - 6
Color is a coloration or tint found in drinking water that can be caused by a variety of metals and compounds that may be present in the water. The color of the water can be used to generally determine the compound in the water. Color change occurs when dissolved or suspended minerals enter into the drinking water. Elevated copper levels may cause blue-green color, while aluminum will cause water to take on a grey hue. The SMCL is 15 C.U. (Color Units). MWRA color levels are well below the MassDEP guidelines.

Copper
	Units	Average	Range
Metro Boston	ug/L	55	0-258
CVA	ug/L	62	8 – 610
Copper is a metal that enters into drinking water due to corrosion from domestic pipes or natural deposits. At high concentrations, the metal can create a metallic taste in drinking water and color the water a blue-green. Copper salts may infrequently be used to control algal blooms. The SMCL of copper is 1000 ug/L and the health based Action Level is 1300 ug/L. The data in the table represent treated water within the distribution system for fully supplied communities. MWRA and CVA community corrosion control treatment reduces the amount of copper corrosion from household plumbing. MWRA copper levels are well below the MassDEP guidelines.

Fluoride
	Units	Average	Range
Metro Boston	mg/L	0.68	0.39 - 0.83
CVA	mg/L	ND	ND
Fluoride is a naturally occurring mineral in the environment that can leach into drinking water from natural deposits. Fluoride is also added at the Carroll Water Treatment Plant to improve dental health and to prevent against cavities at the CDC recommended level of 0.7 mg/L. None of the CVA communities fluoridate their water. Fluoride has an SMCL of 2.0 mg/L for aesthetic concerns and an MCL of 4.0 mg/L for health concerns. MWRA fluoride levels are below the MassDEP guidelines.

Iron
	Units	Average	Range
Metro Boston	ug/L	50.3	16.8 – 197
CVA	ug/L	12.8	7.3 – 22.6
Iron is a metal that naturally occurs in the environment and enters drinking water through rocks and soil deposits. Iron can also be released from older unlined cast iron water mains. The metal may cause drinking water to take on a rusty red or orange color that has a metallic taste. The SMCL for iron is 300 ug/L. MWRA iron levels are below the MassDEP guidelines. However, flow disruption in local water systems from firefighting or main breaks can cause temporary increases in iron levels. MetroBoston values represent distribution system; CVA values represent water delivered to the communities.

Manganese
	Units	Average	Range
Metro Boston	ug/L	7.1	3.7 - 14.4
CVA	ug/L	2.98	1.6 – 4.4
Manganese is a metal that can leach out of manganese deposits in natural sources into water. Manganese may cause water to have a black or brown color, and a metallic taste. Manganese has an SMCL of 50 ug/L. Massachusetts also has a health related guidance value of 300 ug/L. MWRA manganese levels are below both aesthetic and health-related MassDEP guidelines.

Silver
	Units	Average	Range
Metro Boston	ug/L	ND	ND
CVA	ug/L	ND	ND
Silver is a metal that occurs naturally in the environment. The SMCL for silver is 100 ug/L. At higher levels, silver may cause skin or eye discoloration. MWRA typically does not detect any silver.

Sulfate
	Units	Average	Range
Metro Boston	mg/L	6.3	4.9 – 7.8
CVA	mg/L	4.1	3.6 – 5.3
Sulfate is a mineral that can enter drinking water from rocks and soil and from the decay of animal or plant matter in the water source. At elevated levels sulfate can cause drinking water to have a salty taste or a rotten egg smell. The SMCL for sulfate is 250 mg/L. MWRA sulfate levels are well below the MassDEP guidelines.

Total Dissolved Solids (TDS)
	Units	Average	Range
Metro Boston	mg/L	113.5	106 - 118
CVA	mg/L	40.3	34 - 47
Total dissolved solids (TDS) are substances that may enter drinking water sources from runoff and leaching of natural deposits. The addition of treatment chemicals can also increase TDS levels. TDS may include minerals, salts, dissolved metals, and organic matter. At high levels, TDS can cause water hardness and may cause water to have a salty taste. The water may also be colored or stained. Dissolved solids are not known to pose health risks. The SMCL for TDS is 500 mg/L. MWRA TDS levels are well below MassDEP guidelines.

Hardness
	Units	Average	Range
Metro Boston	mg/L	15.1	13.1 - 16.3
CVA	mg/L	7.3	6.9 - 7.6
Water’s “hardness” and “softness” is due to its concentration of minerals—primarily calcium and magnesium. Hardness can be impacted by TDS in water. The lower the mineral concentration, the softer the water is. Hardness affects the efficiency of soaps and laundry detergent when cleaning. MWRA water is soft. Less soap and shampoo are needed for good lathering, and less dishwashing detergent should be used. Hard water would have a value above 75 mg/L. Hardness can also be expressed in terms of grains per gallon. 17.1 mg/l is the equivalent of 1 grain per gallon. MetroBoston water typically has about 1 grain per gallon of hardness, while CVA has closer to ½ grain per gallon.

Zinc
	Units	Average	Range
Metro Boston	ug/L	ND	ND - ND
CVA	ug/L	2.9	2.3 – 3.9
Zinc is a metal that enters drinking water through natural deposit leaching and pipe corrosion. It can also be increased by the use of zinc containing treatment chemicals. The metal can cause water to take on a metallic taste. The SMCL for zinc is 5000 ug/L. MWRA does not use any zinc containing treatment chemicals. MWRA zinc levels are well below the MassDEP guidelines.

Special Initiatives with the Public Health Community

As part of its Water Supply Improvement Program, MWRA has partnered with public health professionals on a series of projects. All of these projects are tied to MWRA's overall program to improve and protect drinking water through cost-effective efforts that are directly related to public health benefits, such as:

Coordination with public health officials and water superintendents	MWRA maintains close working relationships with state and local public health and water officials through an advisory committee and a monthly water quality report. MWRA promotes interaction between health and water departments in all communities.
Cooperative research and surveillance projects	MWRA continues to enhance extensive water quality testing programs and works with state and City of Boston public health agencies to track health outcomes inside and outside the MWRA system and to implement an early-warning system of possible trouble.
Annual water quality report	To help answer customers' questions about their drinking water, MWRA issues an annual water quality report (also known as "consumer confidence report") each June/July.
Lead exposure education efforts	While water is lead-free coming from the reservoir, MWRA has made efforts to make chemistry changes to reduce leaching of lead from homes' lead pipes. MWRA also has a public education campaign to educate homeowners how to reduce lead exposure from drinking water.
Public Health Advisory Group	Experts and practitioners assist MWRA in determining the most cost-effective manner of providing the highest level of public health benefits.

For more information, please contact: Beverly Anderson, MWRA Public Health Project Manager

PAPERS AND FACT SHEETS

Back to the Future:
Water Supply and Public Health — A Mission To Share Nov 1999

Reaching Out to Health Care Providers
Panel Presentation - Making Waves II Mar 2000

Water Supply and Public Health [PDF]

Water and Health

Special Health Considerations: Important Information for People with Weakened Immune Systems

Cryptosporidium and Giardia Information

FOR PEOPLE WITH WEAKENED IMMUNE SYSTEMS OR WITH HIV/AIDS:

EXTRA PRECAUTIONS TO AVOID CRYPTOSPORIDIOSIS & GIARDIASIS

A list of potential contaminants that are routinely tested for in the MWRA water system.

Pesticides and Herbicides

Secondary Contaminants

Special Initiatives with the Public Health Community

Coordination with public health officials and water superintendents

Cooperative research and surveillance projects

Annual water quality report

Lead exposure education efforts

Public Health Advisory Group

PAPERS AND FACT SHEETS

Related Links