Water Quality
Perchlorate is an inorganic compound used as an oxidizer in solid rocket propellant, aerospace fuel, fireworks, and airbag inflators. It has contaminated portions of San Fernando Valley groundwater since at least the mid-twentieth century, when aerospace manufacturing and testing operations expanded through Burbank, Canoga Park, and the Santa Susana mountain corridor. California adopted a maximum contaminant level of 6 micrograms per liter for perchlorate in drinking water in 2007, one of the strictest limits in the country, and far below contamination levels documented in some Colorado River source water that reaches Valley taps. California's own health scientists set a public health goal of 1 microgram per liter in 2015, six times more protective than the legal MCL. No enforceable federal limit exists; the EPA is required to finalize a national rule by May 2027. A standard whole-house carbon filter does not reliably remove perchlorate. An NSF/ANSI 58 certified reverse osmosis system at the drinking tap is the point-of-use technology with the strongest performance record for perchlorate reduction.
Concerned about perchlorate in your SFV home's water?
UpTown Cares has served 2,000+ families across Southern California since 2022. Every install is backed by $2M liability insurance and a lifetime warranty on workmanship. A free in-home water test takes about an hour at your kitchen counter.
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The San Fernando Valley carries one of the most layered water contamination histories of any urban basin in California, shaped by decades of aerospace manufacturing, petroleum refining, and military activity. Most Valley households receive their drinking water from LADWP, which blends Owens Valley aqueduct water, Metropolitan Water District imports (sourced partly from the Colorado River), and treated local groundwater pumped from the SFV basin. Each of those source types brings its own contaminant profile. For perchlorate specifically, the contamination pathway runs from two directions: legacy industrial spills and releases from aerospace sites within the Valley itself, and agricultural runoff and manufacturing residue from the Nevada and Arizona desert corridor that ends up in Colorado River water imported through the MWD system. Understanding both pathways explains why Valley water utilities test for perchlorate quarterly and why California set a regulatory limit far stricter than any federal standard that has existed. For a broader view of what LADWP tests for across all contaminants, see our SFV water quality overview and the utility water quality comparison.
What is perchlorate and where does it come from in the San Fernando Valley?
Perchlorate is a naturally occurring and manufactured inorganic chemical whose primary industrial form, ammonium perchlorate, is the oxidizer in solid rocket fuel. It has been produced, stored, and used extensively across the aerospace corridor stretching from Burbank through Canoga Park into the Santa Susana Mountains. When ammonium perchlorate contacts soil or groundwater, it dissolves readily and migrates with the water table rather than binding to soil particles, which is why contamination spreads far from its original release point and persists for decades after the source activity has ended.
The two primary aerospace sources documented in the San Fernando Valley are the Lockheed manufacturing complex near the Hollywood Burbank Airport and the Rocketdyne propulsion facility in Canoga Park, which operated solid rocket development and testing programs from the 1950s through the late twentieth century. Rocketdyne's operations extended into the Santa Susana Field Laboratory in the Simi Hills, where rocket engine testing created a documented contamination plume that has been the subject of state and federal remediation orders for decades. These facilities used and stored large quantities of ammonium perchlorate on-site, and historic spills and disposal practices introduced the compound into the SFV alluvial basin groundwater. The SFV VOC and groundwater remediation article covers the broader industrial contamination history of the same corridor, including TCE and PCE plumes that originated from the same aerospace era.
The EPA currently oversees four separate Superfund sites in the San Fernando Valley, each associated with different groundwater contaminant plumes from aerospace and industrial activity. In March 2026, the EPA proposed a new cleanup plan for the Area 2 Superfund site near Glendale to accelerate treatment of contaminated groundwater, as documented in the EPA Area 2 Superfund press release. The California Department of Toxic Substances Control maintains a dedicated perchlorate information page at dtsc.ca.gov/perchlorate that catalogs the state's cleanup activities and regulatory history. For Valley homeowners, the key implication is that the SFV groundwater basin is a documented source of perchlorate contamination, and LADWP actively manages that risk through monitoring, well closures, and treatment before water reaches distribution. The chromium-6 article documents a parallel regulatory story for another aerospace-legacy contaminant in the same basin.
What does California's 6 µg/L limit for perchlorate mean in practice?
California's maximum contaminant level of 6 micrograms per liter, enforced by the State Water Resources Control Board since 2007, means that any public water system in the state must take action if perchlorate in finished water exceeds that threshold. The MCL is the legal trigger for remediation, public notification, and switching to alternative sources. It is among the most protective state-level limits in the country, established before any federal MCL existed and driven by California's proximity to the aerospace and military industries responsible for the contamination.
The MCL and the public health goal are two different numbers, and the gap between them is the regulatory story worth understanding. The MCL of 6 µg/L is the enforceable legal limit. The public health goal of 1 µg/L, revised downward by the California Office of Environmental Health Hazard Assessment in 2015, represents the concentration at which scientists consider health risk to be negligible over a lifetime of exposure. That gap of six times between what is legal and what is considered health-safe is not unique to perchlorate in California, but it is one of the larger MCL-to-PHG ratios in the state's regulatory framework. The MCL is set where feasible treatment can reliably achieve it across all water systems; the PHG reflects what the science says is protective regardless of treatment cost. For context, see how California's arsenic MCL and PHG compare, where a similar gap exists between the legal limit and the health-based goal.
| Standard | Level | Set by | Effective |
|---|---|---|---|
| California MCL | 6 µg/L (micrograms per liter) | California DTSC / SWRCB | October 2007 |
| California PHG (health goal) | 1 µg/L | OEHHA (CalEPA), revised 2015 | 2015 |
| Federal MCL | Not yet finalized | EPA (rule due May 2027) | Pending |
The absence of a federal MCL is significant because it means water utilities in states without their own perchlorate standard are not required to test for or report perchlorate levels under federal law. California residents have had regulatory protection since 2007 that most of the country still lacks. The California water quality rules article explains how state standards routinely go beyond federal minimums in this way, particularly for contaminants linked to California's industrial history. For a companion example in the same regulatory pattern, see the gross alpha radioactivity article, where California's standards for naturally occurring radioactive compounds similarly outpace federal minimums.
Does Colorado River source water carry perchlorate into Valley taps?
Yes. The California State Water Resources Control Board has documented perchlorate at levels of 5 to 9 micrograms per liter in Colorado River water, approaching California's MCL of 6 µg/L, with the contamination traced to ammonium perchlorate manufacturing facilities in Nevada. Metropolitan Water District water imported through the Colorado River Aqueduct serves as one component of the blended supply that reaches San Fernando Valley taps through LADWP's distribution system.
LADWP blends water from several sources: Owens Valley aqueduct supply, MWD imports (which include Colorado River and State Water Project water), and treated local groundwater. The perchlorate concentration in any given San Fernando Valley home's tap water depends on which blend LADWP is delivering, which varies by season, drought conditions, and groundwater availability. LADWP publishes quarterly contaminant monitoring results, and the annual Consumer Confidence Report provides detected perchlorate ranges for each source area including the San Fernando Valley. The report covers both the running annual average and the maximum detected level, which is the number that governs regulatory compliance. LADWP's Water Quality Hotline at (213) 367-3182 handles customer inquiries about specific readings.
The Colorado River perchlorate pathway is qualitatively different from the SFV groundwater contamination because it is continuous rather than site-specific. Aerospace legacy contamination in the basin is being actively remediated and wells that exceed limits are taken offline or treated. Colorado River source water perchlorate reflects ongoing production activities in the upper watershed and is managed at the MWD treatment level before distribution to LADWP. Both pathways contribute to why utilities serving the Valley test for perchlorate as a standard monitoring parameter. For more on how LADWP manages source water quality across all monitored parameters, see the SFV utility water quality comparison, which reviews the full contaminant profile across source types.
How does perchlorate affect thyroid function?
Perchlorate blocks the thyroid gland's ability to absorb iodine from the bloodstream by competing with iodide at the sodium-iodide symporter, a membrane transporter the thyroid uses to concentrate iodine for hormone synthesis. The disruption reduces production of thyroid hormones T3 and T4, which regulate metabolism, cardiovascular function, and neurological development throughout life and are particularly critical during fetal development and the first years of a child's life.
The clinical evidence on perchlorate is strongest for populations with pre-existing thyroid conditions, low dietary iodine intake, or higher sensitivity due to life stage. The National Institutes of Health has published peer-reviewed research on perchlorate's pharmacology and human health effects at PMC3640367, which provides a detailed review of epidemiological and clinical findings. Key findings from that literature include:
- Perchlorate inhibits thyroid iodine uptake at doses relevant to drinking water exposure, particularly in individuals with marginal iodine status.
- Pregnant women and fetuses face the highest sensitivity: thyroid hormone disruption during fetal development is associated with impaired neurological outcomes in children.
- Formula-fed infants whose formula is prepared with contaminated tap water face elevated exposure because infants consume more water per body weight than adults.
- People with hypothyroidism, Hashimoto's thyroiditis, or other thyroid conditions may be more sensitive to perchlorate's inhibitory effect at lower exposure levels than the general population.
California's revised PHG of 1 µg/L was driven by these sensitive-population considerations. OEHHA concluded in 2015 that the previous PHG of 6 µg/L did not adequately account for children and pregnant women, and revised it downward by a factor of six. The state has not yet lowered the MCL to match because of the cost and feasibility constraints on water utilities, but the PHG revision signals where the science has moved. For households with pregnant women, formula-fed infants, or members with thyroid conditions, the gap between the MCL (6 µg/L) and the health goal (1 µg/L) is a meaningful consideration when evaluating whether to use point-of-use filtration. See the SFV tap water safety overview for a broader look at how these risk factors interact across the full contaminant profile of Valley water.
Does LADWP test for perchlorate in San Fernando Valley tap water?
Yes. LADWP tests for perchlorate quarterly across its distribution zones and publishes the results annually in the Consumer Confidence Report. The SFV-area results appear under the San Fernando Valley service area columns in that report, alongside results from the Los Angeles Aqueduct Filtration Plant and MWD Jensen Plant sources. The utility has historically reported perchlorate results for Valley tap water below the California MCL of 6 µg/L, and publishes both the detected range and the running annual average.
LADWP also monitors at the well level before groundwater enters distribution. Wells that test at or near the MCL are either taken offline, blended with lower-concentration sources to reduce the average, or treated before entering the distribution system. This is the same management approach LADWP applies to chromium-6 and PFAS from contaminated wells, as described in the PFAS in SFV water article and the lead in SFV water article. The utility's well-management decisions are not always visible in the Consumer Confidence Report's finished-water numbers, which show the result after blending and treatment rather than raw well levels.
For any household with questions about a specific perchlorate reading, LADWP's Water Quality Hotline at (213) 367-3182 handles customer inquiries. The UpTown Cares water testing service is an option for households that want an independent in-home measurement rather than relying solely on the utility's system-wide average. Our water quality resource page links to the most recent LADWP annual reports alongside state and federal data. The whole-house water filtration explainer describes how municipal treatment differs from household treatment and why municipal monitoring results do not resolve the question of what to do at the household level for sensitive populations.
What filter technologies remove perchlorate from drinking water?
Reverse osmosis systems certified to NSF/ANSI Standard 58 are the most widely available and consistently effective residential option for perchlorate reduction. Ion exchange with a specialized anion exchange resin also removes perchlorate effectively and is used in some municipal treatment systems. Standard carbon-based filters, including whole-house carbon block and pitcher filters, do not remove perchlorate because it does not adsorb to carbon media.
| Technology | Effective for perchlorate? | Notes |
|---|---|---|
| Reverse osmosis (NSF/ANSI 58) | Yes | Point-of-use under-sink systems; certified for perchlorate reduction; addresses chromium-6, lead, PFAS, and nitrate simultaneously |
| Anion exchange resin (specialized) | Yes | Used in some municipal systems; residential anion exchange units are available but less common than RO for household use |
| Granular activated carbon (standard) | No | Perchlorate is an ionic compound and does not adsorb to standard carbon media |
| Whole-house carbon block | No | Effective for chlorine, taste, and some organics; not rated for perchlorate or other ionic contaminants |
| Pitcher filter (carbon bead) | No | Carbon-based media; same limitation as other carbon technologies for ionic contaminants |
The practical recommendation for SFV households concerned about perchlorate is an NSF/ANSI 58-certified RO system at the kitchen sink. That single system addresses perchlorate and also reduces chromium-6, lead, arsenic, PFAS, and nitrate simultaneously, which is the most cost-efficient approach for a region where all of those contaminants are part of the water quality history. The reverse osmosis vs. whole-house filtration comparison explains when RO at the tap is sufficient and when adding a whole-house stage makes sense for a given household. Our RO installation service covers NSF-certified under-sink systems across the San Fernando Valley, and our whole-house filtration service handles households that want additional pre-filter stages throughout the home. The SFV chromium-6 article includes a parallel filter technology comparison for that contaminant, since the same RO system addresses both.
Should San Fernando Valley homeowners install a filter specifically for perchlorate?
LADWP tap water in the San Fernando Valley is monitored quarterly for perchlorate and has historically tested below California's MCL of 6 µg/L. For most households drawing on the treated municipal supply, the immediate regulatory risk is managed by the utility. The question becomes more relevant for households with pregnant women, formula-fed infants, or members with thyroid conditions, for whom the gap between the MCL (6 µg/L) and California's own health goal (1 µg/L) represents a meaningful exposure consideration that the utility average does not resolve at the household level.
The case for an RO system in the SFV is rarely built on perchlorate alone. Valley tap water carries a documented history of chromium-6, lead from aging interior plumbing, PFAS from groundwater plumes, and nitrate from agricultural legacy. Perchlorate adds another layer to the same picture. An NSF/ANSI 58-certified RO system at the drinking tap addresses all of these simultaneously for a few hundred dollars of installed equipment, which is why it is the most commonly recommended residential treatment approach for Valley households who want a comprehensive solution. You do not need to know the exact perchlorate concentration in your tap water to make the decision; the system reduces a range of contaminants that are documented in SFV source water as a matter of public record.
For households on private wells rather than LADWP supply, the calculus is different: well water perchlorate levels can vary significantly from the municipal average depending on the well's location relative to documented contamination plumes from the Burbank and Canoga Park aerospace corridors. The private well testing article covers the SFV-specific test panel recommended for well owners, including perchlorate for wells near former aerospace sites. If you are on municipal LADWP water and want an independent in-home measurement before deciding on treatment, our water testing service collects a sample from your kitchen tap and runs a panel that includes perchlorate alongside hardness, TDS, and other key parameters. See the hardness by zip code guide for how that same testing approach applies to the mineral profile that shapes your overall treatment decision. Our About page covers the company background, licensing, and insurance for homeowners evaluating providers in North Hollywood, Studio City, Burbank, Glendale, Pasadena, Sherman Oaks, Van Nuys, Encino, Woodland Hills, Tarzana, Calabasas, Northridge, Reseda, Canoga Park, and surrounding communities.
Ready to test your SFV home's water for perchlorate and other contaminants?
UpTown Cares has served 2,000+ families across Southern California since 2022. Every install is backed by $2M liability insurance and a lifetime warranty on workmanship. Our free in-home water test covers perchlorate alongside hardness, TDS, and other key parameters. We carry out 2 to 4 hour whole-house and RO system installations.
Book a free water test or call (213) 838-9330.
Frequently Asked Questions
Is perchlorate in San Fernando Valley tap water a health risk?
LADWP-supplied tap water in the SFV has historically measured below California's MCL of 6 µg/L for perchlorate. California's own health scientists set a more protective goal of 1 µg/L in 2015, which is most relevant for pregnant women, formula-fed infants, and people with thyroid conditions who may be more sensitive to perchlorate's effect on thyroid iodine uptake at lower exposure levels.
What is California's legal limit for perchlorate in drinking water?
California's maximum contaminant level for perchlorate is 6 micrograms per liter, established in 2007 by the State Water Resources Control Board. No enforceable federal MCL exists as of 2026; the EPA is required to finalize a national rule by May 2027. California's standard is among the strictest in the nation and applies to all public water systems, including LADWP serving the San Fernando Valley.
Does a whole-house carbon filter remove perchlorate from drinking water?
No. Perchlorate is an ionic compound that does not adsorb to activated carbon or carbon block media. Standard whole-house carbon filters are effective for chlorine, taste, odor, and some organic compounds, but are not rated for perchlorate reduction. An NSF/ANSI 58 certified reverse osmosis system at the drinking tap is the appropriate residential treatment for perchlorate, and also addresses chromium-6, lead, arsenic, PFAS, and nitrate.
Where did perchlorate in San Fernando Valley groundwater come from?
The primary documented sources are aerospace manufacturing and rocket propellant operations at facilities including Lockheed near Burbank Airport and Rocketdyne in Canoga Park, active from the 1950s through the late twentieth century. Ammonium perchlorate used in solid rocket fuel dissolved into soil and groundwater from historic spills and disposal practices. Colorado River imported water also carries perchlorate at levels of 5 to 9 micrograms per liter as documented by the California State Water Resources Control Board.
Does LADWP notify customers when perchlorate is detected?
LADWP reports perchlorate detections in its annual Consumer Confidence Report, required by law and delivered to customers by July 1 each year for prior-year data. If perchlorate exceeds the California MCL of 6 micrograms per liter in the distribution system, LADWP is required under state law to issue a public notice and take corrective action before the water continues reaching customers in that zone.
Can a reverse osmosis system at the kitchen tap remove perchlorate?
Yes. An NSF/ANSI 58 certified reverse osmosis system reduces perchlorate at the drinking tap. The same system also reduces chromium-6, lead, arsenic, PFAS, and nitrate, making it the most multi-functional point-of-use option for San Fernando Valley households concerned about the region's documented water quality history. Look for the NSF 58 certification mark specifically when evaluating systems.
