The Power of Information

National Drinking Water Database

San Jose Water Company Utilities - San Jose, CA

Serves 979,000 people


Perchlorate is a synthetic oxygen additive in solid fuel propellant for rockets, missiles, and fireworks, and is primarily used by the military and the space industry; it may occur naturally in certain imported agricultural fertilizers.
This Drinking Water System
Test Days Exceeding Health GuidelinesDefinition of what this is
0 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
67 days
Tests ConductedNumber of individual tests done for this contaminant
188 tests

Testing Summary

Health Limit
Legal Limit

Testing History

-Tested      -Detected      -Over Health Guidelines      -Over Legal Limit*
PerchloratePerchlorate is a synthetic oxygen additive in solid fuel propellant for rockets, missiles, and fireworks, and is primarily used by the military and the space industry; it may occur naturally in certain imported agricultural fertilizers.0 ppb
0 ppb
5 ppb
Legal at any levelThis is the Federal Limit. State Limits may be lower.
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 Perchlorate

Health Based Limits for Perchlorate

Health-Based Screening LevelA benchmark concentration of contaminants in water that may be of potential concern for human health, if exceeded. For noncarcinogens, the HBSL represents the contaminant concentration in drinking water that is not expected to cause any adverse effects over a lifetime of exposure. For carcinogens, the HBSL range represents the contaminant concentration in drinking water that corresponds to an excess estimated lifetime cancer risk of 1 chance in 1 million to 1 chance in 10 thousand. Source: U.S. Geological Survey.5 ppb
California Public Health GoalsDefined by the State of California Office of Environmental Health Hazard Assessment (OEHHA) as the level of contaminant that is allowed in drinking water. For acutely toxic substances, levels are set at which scientific evidence indicates that no known or anticipated adverse effects on health will occur, plus an adequate margin-of safety. PHGs for carcinogens or other substances which can cause chronic disease shall be based solely on health effects without regard to cost impacts and shall be set at levels which OEHHA has determined do not pose any significant risk to health.6 ppb

Testing Results

Testing DateAverage
Samples taken that dayNumber of Non-DetectsRange of Results
2009-04-020 ppb110 ppb
2009-04-010 ppb110 ppb
2009-03-240 ppb220 ppb
2009-03-180 ppb110 ppb
2009-03-110 ppb220 ppb
2009-03-090 ppb110 ppb
2009-02-240 ppb220 ppb
2009-02-090 ppb110 ppb
2009-01-070 ppb110 ppb
2008-12-150 ppb220 ppb
2008-12-110 ppb110 ppb
2008-12-100 ppb110 ppb
2008-12-030 ppb110 ppb
2008-11-190 ppb110 ppb
2008-11-180 ppb220 ppb
2008-10-210 ppb110 ppb
2008-10-080 ppb220 ppb
2008-10-070 ppb110 ppb
2008-10-060 ppb550 ppb
2008-09-290 ppb220 ppb
2008-09-230 ppb220 ppb
2008-09-220 ppb440 ppb
2008-09-170 ppb440 ppb
2008-09-100 ppb660 ppb
2008-09-090 ppb440 ppb
2008-08-210 ppb110 ppb
2008-08-190 ppb110 ppb
2008-08-130 ppb110 ppb
2008-08-120 ppb330 ppb
2008-08-110 ppb440 ppb
2008-08-070 ppb660 ppb
2008-08-060 ppb440 ppb
2008-08-050 ppb770 ppb
2008-08-040 ppb110 ppb
2008-07-160 ppb220 ppb
2008-07-090 ppb550 ppb
2008-07-080 ppb110 ppb
2008-07-020 ppb11110 ppb
2008-07-010 ppb770 ppb
2008-05-050 ppb110 ppb
2008-04-300 ppb330 ppb
2008-04-170 ppb220 ppb
2008-04-160 ppb220 ppb
2008-03-270 ppb110 ppb
2008-03-130 ppb220 ppb
2008-03-120 ppb660 ppb
2008-03-110 ppb550 ppb
2008-03-050 ppb770 ppb
2008-03-040 ppb440 ppb
2008-02-280 ppb220 ppb
2008-02-270 ppb110 ppb
2008-02-260 ppb220 ppb
2008-02-200 ppb440 ppb
2008-02-190 ppb110 ppb
2008-02-120 ppb440 ppb
2008-02-110 ppb220 ppb
2008-02-070 ppb330 ppb
2008-02-060 ppb440 ppb
2008-02-050 ppb330 ppb
2008-01-150 ppb440 ppb
2008-01-140 ppb330 ppb
2008-01-100 ppb10100 ppb
2008-01-090 ppb330 ppb
2007-04-190 ppb110 ppb
2007-03-280 ppb110 ppb
2007-03-050 ppb110 ppb
2007-01-300 ppb110 ppb