The Power of Information

National Drinking Water Database


Chelmsford Water District Utilities - Cambridge, MA


Serves 25,393 people

Total trihalomethanes (TTHMs)

Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.
 
This Drinking Water System
Test Days Exceeding Health GuidelinesDefinition of what this is
51 days
Test Days Exceeding Legal LimitsNumber of days in which the samples taken in that day exceed the Maximum Contaminant Level (Depending on the contaminant and its MCL, that may or may not trigger an MCL violation. Some MCLs are based on averages spanning several months to a year)
0 days
Test DaysNumber of days in which this chemical has reported results in the data we received from the State
65 days
Tests ConductedNumber of individual tests done for this contaminant
238 tests

Testing Summary

ContaminantAverage/
Maximum
Result
Health Limit
Exceeded
Legal Limit
Exceeded

Testing History

-Tested      -Detected      -Over Health Guidelines      -Over Legal Limit*
Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.20.9 ppb
71 ppb
Yes
9.8 ppb
No
80 ppb
NOTE: Each dot in the above graph represents one month.
* Water utilities are noted as exceeding the legal limit if any test is above the maximum contaminant level (MCL). Most MCLs are based on annual averages so exceeding the MCL for one test does not necessarily indicate that the system is out of compliance.

Health Based and Legal Limits for Total trihalomethanes (TTHMs)

Health Based Limits for Total trihalomethanes (TTHMs)

StandardDescriptionLevel
One in one million (10-6) Cancer RiskThe concentration of a chemical in drinking water corresponding to an excess estimated lifetime cancer risk of 1 in 1,000,000. Source: U.S. Environmental Protection Agency.9.8 ppb
EPA Human Health Water Quality CriteriaWater quality criteria set by the US EPA provide guidance for states and tribes authorized to establish water quality standards under the Clean Water Act (CWA) to protect human health. These are non-enforceable standards based upon exposure by both drinking water and the contribution of water contamination to other consumed foods. Source: U.S. Environmental Protection Agency.11.5 ppb
Maximum Contaminant Limit (MCL)The enforceable standard which defines the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to health-based limits (Maximum Contaminant Level Goals, or MCLGs) as feasible using the best available analytical and treatment technologies and taking cost into consideration. Source: U.S. Environmental Protection Agency.80 ppb
Lifetime health-based limit, non-cancer riskConcentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for a lifetime of exposure. The Lifetime health-based limit (or Health Advisory, HA) is based on exposure for a a 70-kg adult consuming 2 liters of water per day. Source: U.S. Environmental Protection Agency.130 ppb
One in ten thousand (10-4) Cancer RiskThe concentration of a chemical in drinking water corresponding to an excess estimated lifetime cancer risk of 1 in 10,000. Source: U.S. Environmental Protection Agency.980 ppb
Drinking Water Equivalent LevelA lifetime exposure concentration protective of adverse, noncarcinogenic health effects, that assumes all of the exposure to a contaminant is from drinking water. Source: U.S. Environmental Protection Agency.1835 ppb
Children's health-based limit for 10-day exposureConcentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic effects for up to ten days of exposure. The Ten-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.4860 ppb
Children's health-based limit for 1-day exposureConcentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for up to one day of exposure. The One-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.10600 ppb

Testing Results

Testing DateAverage
Result
Samples taken that dayNumber of Non-DetectsRange of Results
2009-05-050.7 ppb100.7 ppb
2009-05-0415 ppb3015 ppb
2009-04-1321 ppb3021 ppb
2009-03-060.8 ppb100.6 to 1 ppb
2009-02-0210.9 ppb3010.9 ppb
2009-01-1544.83 ppb6012 to 65 ppb
2008-12-0831 ppb3031 ppb
2008-11-0522.9 ppb3012.8 to 33 ppb
2008-10-0840.83 ppb6014 to 59 ppb
2008-10-0713.25 ppb308.5 to 18 ppb
2008-09-0814 ppb3014 ppb
2008-08-1850.67 ppb6015 to 80 ppb
2008-07-144.5 ppb404.5 ppb
2008-06-1318 ppb3018 ppb
2008-05-0714.75 ppb3010.5 to 19 ppb
2008-04-1031.13 ppb609 to 47 ppb
2008-03-0715 ppb3012 to 18 ppb
2008-02-2114 ppb3010 to 18 ppb
2008-01-1871 ppb1071 ppb
2008-01-1744.8 ppb5014 to 67 ppb
2007-12-0615.8 ppb307.6 to 24 ppb
2007-11-1917.4 ppb3013.8 to 21 ppb
2007-10-1613 ppb3013 ppb
2007-10-1540 ppb6020 to 51 ppb
2007-09-1322 ppb3022 ppb
2007-08-0863 ppb3063 ppb
2007-07-1145.67 ppb3019 to 59 ppb
2007-07-1020.75 ppb406 to 53 ppb
2007-06-0765.85 ppb3036.7 to 95 ppb
2007-05-0118 ppb1018 ppb
2007-04-3034 ppb607 to 68 ppb
2007-04-119 ppb309 ppb
2007-03-0619 ppb3019 ppb
2007-02-0114 ppb3013 to 15 ppb
2007-01-3127 ppb3027 ppb
2007-01-2522.29 ppb707 to 45 ppb
2007-01-246.4 ppb405.8 to 7 ppb
2006-11-0314.4 ppb305.8 to 23 ppb
2006-10-1833.57 ppb707 to 61 ppb
2006-09-200.9 ppb100.9 ppb
2006-08-070.8 ppb100.8 ppb
2006-07-1932.59 ppb703.5 to 68 ppb
2006-07-1233 ppb3033 ppb
2006-04-2625.86 ppb709 to 44 ppb
2006-02-1818 ppb3018 ppb
2006-02-150.5 ppb100.5 ppb
2006-01-3114 ppb306 to 22 ppb
2005-12-1416.3 ppb3012.6 to 20 ppb
2005-11-1044.9 ppb2033.9 to 55.9 ppb
2005-11-0925 ppb3025 ppb
2005-11-0825.52 ppb501.6 to 73 ppb
2005-09-0818 ppb3018 ppb
2005-08-0818.14 ppb707 to 48 ppb
2005-07-190.5 ppb100.5 ppb
2005-06-131 ppb101 ppb
2005-05-011 ppb101 ppb
2005-04-267.86 ppb700.6 to 12 ppb
2005-02-1523 ppb4023 ppb
2005-02-1412.31 ppb700.8 to 25 ppb
2004-11-165.25 ppb610 to 15 ppb
2004-08-109.93 ppb410 to 23 ppb
2004-08-0918 ppb2015 to 21 ppb
2004-05-1914.38 ppb610 to 22 ppb
2004-03-090 ppb400 ppb
2004-03-0811.32 ppb607 to 15 ppb