The Power of Information

National Drinking Water Database


City of Modesto Utilities - Modesto, CA


Serves 190,106 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
28 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
220 days
Tests ConductedNumber of individual tests done for this contaminant
620 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.4.6 ppb
47 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
2009-03-260 ppb110 ppb
2009-03-248.66 ppb1160 to 47 ppb
2009-03-190 ppb110 ppb
2009-03-176.42 ppb1570 to 40 ppb
2009-03-161.5 ppb101.5 ppb
2009-03-102.1 ppb1590 to 15 ppb
2009-03-036.27 ppb17100 to 45 ppb
2008-12-0213.48 ppb200.96 to 26 ppb
2008-11-182.7 ppb102.7 ppb
2008-11-050.84 ppb100.84 ppb
2008-10-013.05 ppb202.1 to 4 ppb
2008-09-2411.92 ppb520 to 42 ppb
2008-09-173.05 ppb19150 to 37 ppb
2008-09-102.59 ppb21120 to 23 ppb
2008-09-031.3 ppb1680 to 8.3 ppb
2008-08-252 ppb102 ppb
2008-08-059.3 ppb109.3 ppb
2008-07-282 ppb201.7 to 2.3 ppb
2008-07-250 ppb110 ppb
2008-07-142.95 ppb202.6 to 3.3 ppb
2008-07-081.9 ppb101.9 ppb
2008-06-234.1 ppb104.1 ppb
2008-06-170.66 ppb100.66 ppb
2008-06-123.6 ppb202.3 to 4.9 ppb
2008-06-030 ppb110 ppb
2008-05-220 ppb110 ppb
2008-05-190 ppb110 ppb
2008-05-070 ppb110 ppb
2008-04-292.19 ppb310 to 6 ppb
2008-04-230 ppb110 ppb
2008-04-170 ppb110 ppb
2008-03-280.66 ppb100.66 ppb
2008-03-274.91 ppb950 to 37 ppb
2008-03-245.07 ppb310 to 8.6 ppb
2008-03-1916.53 ppb620 to 49 ppb
2008-03-185.63 ppb720 to 27 ppb
2008-03-175.06 ppb520 to 19 ppb
2008-03-129.07 ppb510 to 21 ppb
2008-03-110.46 ppb850 to 2.1 ppb
2008-03-1014.4 ppb410 to 46 ppb
2008-03-054.1 ppb310 to 9.6 ppb
2008-03-0411 ppb640 to 46 ppb
2008-03-038.8 ppb530 to 24 ppb
2008-02-195.6 ppb105.6 ppb
2007-12-176.5 ppb106.5 ppb
2007-11-150 ppb110 ppb
2007-11-130 ppb110 ppb
2007-11-050 ppb110 ppb
2007-10-020 ppb220 ppb
2007-09-2625 ppb420 to 63 ppb
2007-09-250.22 ppb540 to 1.1 ppb
2007-09-243.23 ppb310 to 5.2 ppb
2007-09-196.44 ppb970 to 37 ppb
2007-09-182.17 ppb650 to 13 ppb
2007-09-174.73 ppb310 to 13 ppb
2007-09-124 ppb430 to 16 ppb
2007-09-110.08 ppb980 to 0.69 ppb
2007-09-104.67 ppb320 to 14 ppb
2007-09-0510.88 ppb420 to 43 ppb
2007-09-041.03 ppb1290 to 6.4 ppb
2007-09-030 ppb220 ppb
2007-08-150 ppb110 ppb
2007-08-140 ppb110 ppb
2007-08-070 ppb220 ppb
2007-07-170 ppb110 ppb
2007-07-100.9 ppb100.9 ppb
2007-07-030.26 ppb210 to 0.51 ppb
2007-06-130 ppb110 ppb
2007-06-120 ppb110 ppb
2007-06-050 ppb220 ppb
2007-05-010.47 ppb210 to 0.93 ppb
2007-04-170 ppb220 ppb
2007-04-033.17 ppb310 to 6.1 ppb
2007-03-062.47 ppb310 to 4.6 ppb
2007-02-281.1 ppb101.1 ppb
2007-02-272 ppb102 ppb
2007-02-211.5 ppb101.5 ppb
2007-02-136.9 ppb106.9 ppb
2007-02-062.3 ppb310 to 4.1 ppb
2007-01-025.85 ppb410 to 16 ppb
2006-12-070 ppb110 ppb
2006-12-052.08 ppb410 to 4.3 ppb
2006-11-132.8 ppb210 to 5.6 ppb
2006-11-073.7 ppb201.5 to 5.9 ppb
2006-10-034.83 ppb401.4 to 15 ppb
2006-09-050.58 ppb530 to 1.7 ppb
2006-08-290.26 ppb210 to 0.51 ppb
2006-08-230 ppb110 ppb
2006-08-220 ppb330 ppb
2006-08-150.26 ppb320 to 0.78 ppb
2006-08-080.24 ppb320 to 0.72 ppb
2006-08-012.5 ppb410 to 7.4 ppb
2006-07-250.28 ppb210 to 0.55 ppb
2006-07-180.4 ppb320 to 1.2 ppb
2006-07-110.9 ppb210 to 1.8 ppb
2006-07-051.5 ppb410 to 2.5 ppb
2006-06-290.95 ppb210 to 1.9 ppb
2006-06-280 ppb110 ppb
2006-06-270 ppb110 ppb
2006-06-212.8 ppb320 to 8.4 ppb
2006-06-201 ppb210 to 2 ppb
2006-06-130.47 ppb320 to 1.4 ppb
2006-06-070 ppb110 ppb
2006-06-061.63 ppb410 to 3.4 ppb
2006-05-310.75 ppb210 to 1.5 ppb
2006-05-231 ppb210 to 2 ppb
2006-05-160.95 ppb210 to 1.9 ppb
2006-05-094.2 ppb104.2 ppb
2006-05-080.77 ppb320 to 2.3 ppb
2006-05-0320.5 ppb210 to 41 ppb
2006-05-024.15 ppb620 to 15 ppb
2006-04-120.52 ppb100.52 ppb
2006-04-110 ppb110 ppb
2006-04-050.3 ppb210 to 0.6 ppb
2006-04-044.83 ppb620 to 22 ppb
2006-03-0814.5 ppb210 to 29 ppb
2006-03-077.8 ppb410 to 22 ppb
2006-03-0247 ppb1047 ppb
2006-02-224.1 ppb104.1 ppb
2006-02-150 ppb110 ppb
2006-02-1416.5 ppb2012 to 21 ppb
2006-02-077.32 ppb610 to 20 ppb
2006-02-010 ppb110 ppb
2006-01-036.88 ppb410 to 14 ppb
2005-12-270 ppb110 ppb
2005-12-200 ppb110 ppb
2005-12-130 ppb110 ppb
2005-12-079.25 ppb202.5 to 16 ppb
2005-12-068.5 ppb210 to 17 ppb
2005-11-2311 ppb1011 ppb
2005-11-223.8 ppb103.8 ppb
2005-11-082.9 ppb102.9 ppb
2005-11-014.5 ppb204.1 to 4.9 ppb
2005-10-252 ppb102 ppb
2005-10-1930.5 ppb2020 to 41 ppb
2005-10-120 ppb110 ppb
2005-10-110 ppb110 ppb
2005-10-057.7 ppb107.7 ppb
2005-10-042.2 ppb102.2 ppb
2005-09-272.1 ppb300.51 to 3.2 ppb
2005-09-2126 ppb1026 ppb
2005-09-202.6 ppb102.6 ppb
2005-09-131.64 ppb200.67 to 2.6 ppb
2005-09-063.05 ppb300.64 to 6.4 ppb
2005-09-017.9 ppb107.9 ppb
2005-08-242.2 ppb102.2 ppb
2005-08-170 ppb110 ppb
2005-08-162.1 ppb102.1 ppb
2005-08-101.9 ppb101.9 ppb
2005-08-090 ppb110 ppb
2005-08-030.4 ppb430 to 1.6 ppb
2005-08-020 ppb110 ppb
2005-07-271.05 ppb210 to 2.1 ppb
2005-07-261.3 ppb101.3 ppb
2005-07-201.3 ppb101.3 ppb
2005-07-192.6 ppb201.8 to 3.4 ppb
2005-07-130.9 ppb100.9 ppb
2005-07-1237 ppb1037 ppb
2005-07-062.95 ppb310 to 7.9 ppb
2005-07-051.4 ppb101.4 ppb
2005-06-281.63 ppb410 to 3.3 ppb
2005-06-222.3 ppb210 to 4.6 ppb
2005-06-150.35 ppb210 to 0.7 ppb
2005-06-144.2 ppb210 to 8.4 ppb
2005-06-080 ppb110 ppb
2005-06-072.72 ppb530 to 11 ppb
2005-06-020 ppb110 ppb
2005-06-013.3 ppb210 to 6.6 ppb
2005-05-310 ppb110 ppb
2005-05-250 ppb110 ppb
2005-05-240 ppb220 ppb
2005-05-170 ppb110 ppb
2005-05-120 ppb110 ppb
2005-05-110 ppb110 ppb
2005-05-104.5 ppb430 to 18 ppb
2005-05-040 ppb110 ppb
2005-05-032.95 ppb420 to 8.5 ppb
2005-04-2615.5 ppb210 to 31 ppb
2005-04-130.69 ppb100.69 ppb
2005-04-062.07 ppb200.73 to 3.4 ppb
2005-04-0511.75 ppb207.5 to 16 ppb
2005-03-2421.33 ppb310 to 35 ppb
2005-03-174.1 ppb104.1 ppb
2005-03-1043.33 ppb3016 to 72 ppb
2005-03-038.32 ppb510 to 24 ppb
2005-02-245.5 ppb210 to 11 ppb
2005-02-0316.67 ppb310 to 36 ppb
2005-01-2724 ppb1024 ppb
2005-01-204.4 ppb104.4 ppb
2005-01-1318 ppb1018 ppb
2005-01-068.17 ppb302.5 to 11 ppb
2004-12-235 ppb105 ppb
2004-12-099.2 ppb208.5 to 9.9 ppb
2004-11-185.15 ppb200.6 to 9.7 ppb
2004-11-0421.97 ppb309.9 to 34 ppb
2004-10-143.13 ppb310 to 5 ppb
2004-10-075.3 ppb301.6 to 12 ppb
2004-09-161.9 ppb101.9 ppb
2004-09-092.45 ppb210 to 4.9 ppb
2004-09-020 ppb110 ppb
2004-08-123.31 ppb950 to 27 ppb
2004-08-051.87 ppb320 to 5.6 ppb
2004-07-220 ppb110 ppb
2004-07-150 ppb220 ppb
2004-07-082 ppb320 to 6 ppb
2004-06-100 ppb110 ppb
2004-06-070 ppb110 ppb
2004-06-030.21 ppb320 to 0.64 ppb
2004-05-130 ppb220 ppb
2004-05-060.68 ppb430 to 2.7 ppb
2004-04-2932 ppb1032 ppb
2004-04-155.51 ppb510 to 20 ppb
2004-04-082.1 ppb520 to 4.4 ppb
2004-03-1825 ppb1025 ppb
2004-03-110 ppb220 ppb
2004-03-0414.46 ppb510 to 47 ppb
2004-02-120.99 ppb420 to 3.4 ppb
2004-02-053.23 ppb420 to 12 ppb
2004-01-1510 ppb1010 ppb
2004-01-0820 ppb1020 ppb