UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF

CHEMICAL SAFETY AND

POLLUTION PREVENTION

MEMORANDUM

Date: October 14, 2015

SUBJECT: Lithium Hypochlorite, Human Health and Ecological Preliminary Risk 

Assessment for Registration Review.

PC Code: 014702 DP Barcode: 429326

Risk Assessment Type: Single chemical Regulatory Action: Registration Review PRA

TXR No.: NA Case No.: 3084

MRID Nos.: Multiple, see reference CAS No.: 13840-33-0

FROM: Jonathan Leshin, Toxicologist

Diana Hsieh, Biologist

W. Erickson, Biologist 

Timothy Dole, CIH, Industrial Hygienist

Risk Assessment and Science Support Branch, Antimicrobial Division (7510P)

Office of Pesticide Programs

THROUGH: Laura Parsons, Associate Branch Chief

Steven Weiss, Branch Chief

Risk Assessment and Science Support Branch, Antimicrobial Division (7510P)

Office of Pesticide Programs

TO: Donna Kamarei, Chemical Review Manager

Rose Kyprianou, Re-evaluation Team Leader

Lance Wormell, Branch Chief

Regulatory Management Branch 2

Antimicrobial Division (7510P)

This document provides the preliminary human health and ecological risk assessment conducted 

in support of registration review for Lithium Hypochlorite (PC Code 014702). The Registration 

Review information can be found in the public docket: EPA-HQ-OPP-2013-0606.
2

Table of Contents

EXECUTIVE SUMMARY ............................................................................................................ 4

1.0 INTRODUCTION .................................................................................................................. 5

1.1 Case Overview ................................................................................................................. 5

1.2 Use Characterization ........................................................................................................ 5

2.0 ENVIRONMENTAL FATE ASSESSMENT ........................................................................ 5

3.0 HUMAN HEALTH RISK ASSESSMENT............................................................................ 6

3.1 Human Health Hazard...................................................................................................... 6

3.2 Dietary Assessment.......................................................................................................... 7

3.3 Residential Assessment.................................................................................................... 7

3.4 Aggregate and Cumulative Exposure............................................................................... 7

3.5 Occupational Assessment................................................................................................. 7

3.6 Endocrine Disruptor Screening Program (EDSP)............................................................ 7

4.0 ECOLOGICAL ASSESSMENT ............................................................................................ 8

4.1 Characterization of Ecotoxicity........................................................................................ 8

4.2 Characterization of Exposure ........................................................................................... 9

4.3 Risk Characterization ..................................................................................................... 10

4.4 Listed Species of Concern.............................................................................................. 11

5.0 REFERENCES ..................................................................................................................... 13

APPENDIX A: Summary of Ecotoxicity Data............................................................................ 14

List of Tables

Table 1 Acute Toxicity to Freshwater Fish .............................................................. 15

Table 2 Toxicity to Freshwater Invertebrates ........................................................... 15

Table 3 Avian Acute-oral and Dietary Toxicity ........................................................ 16

Table 4 Comparative toxicity of Chlorine and Hypochlorites ......................................... 18

Table 5 Toxicity of LiCl to Fish and Aquatic Invertebrates .......................................... 19
3

TERMS, ABBREVIATIONS AND SYMBOLS

% percent

μg microgram

μg/L microgram per liter

AD Antimicrobials Division

AI or ai active ingredient

CAS Chemical Abstracts Service 

CFR Code of Federal Regulations 

EC50 median (or 50 percent) effect concentration

ECOTOX ECOTOXicology

EDSP Endocrine Disruptor Screening Program

EEC estimated environmental concentration

EP End-use product

EPA Environmental Protection Agency 

FFDCA Federal Food, Drug, and Cosmetic Act

FIFRA Federal Insecticide, Fungicide, and Rodenticide Act

g gram

L liter

LC50 median (or 50 percent) lethal concentration

LD50 median (or 50 percent) lethal dose

mg/L milligram per liter

MRID Master Record Identification (number)

NA not applicable

nm nanometers

NOAEC no-observed-adverse-effect-concentration

NPDES National Pollutant Discharge Elimination System

OCSPP Office of Chemical Safety and Pollution Prevention

OPP Office of Pesticide Programs

PAI pure active ingredient

PC Code Pesticide Chemical Code

pH power of hydrogen or power of the concentration of the hydrogen ion

pKa power of the acid dissociation constant or negative base-10 logarithm of the acid 

dissociation constant of a solution

ppm parts per million

RED Reregistration Eligibility Decision

WWTPs wastewater treatment plants
4

EXECUTIVE SUMMARY

Lithium hypochlorite is registered for use to control bacteria and algae in swimming pools, hot 

tubs and spas. It is reported to be used in less than one percent of treated pools, due to relative 

costs associated with this product.

Lithium hypochlorite has two active moieties for human health toxicity. When dissolved in water 

lithium hypochlorite forms lithium and chloride ions; these ions are not considered adverse at the 

exposure levels expected. Exposure levels expected of lithium are well below the level of lithium 

found in over the counter lithium salts.

Treated water from swimming pools, hot tubs, and spas can be discharged in various ways. 

However, product labels do not specify any means of discharge. Improper discharge into storm 

drains or surface water can lead to possible contamination of water bodies. There is no 

monitoring data for lithium and chlorine concentrations in receiving waters, and the Agency has 

no models to estimate such concentrations. Therefore a qualitative risk assessment has been 

conducted.

Lithium hypochlorite is moderately to highly toxic to aquatic organisms and practically nontoxic 

to birds. The available data suggests that lithium does not contribute significantly to toxicity, but 

the chlorine released when lithium hypochlorite dissociates is very highly toxic to aquatic 

organisms. Because chlorine dissipates rapidly, chronic exposure is not expected even if chlorine 

residues reach surface water.

The risk assessment concludes that lithium in swimming pool, hot tub, or spa water discharge 

does not adversely affect aquatic organisms, however any chlorine residues have the potential to 

acutely adversely affect aquatic organisms. However, proper disposal methods (e.g., discharge 

into sanitary sewer systems, dechlorination prior to discharge) can minimize those risks. The risk 

assessment suggests this should be required on product labels.
5

1.0 INTRODUCTION

Lithium hypochlorite is currently used as a sanitizer/algaecide in swimming pools and as a 

sanitizer in hot tubs and spas. Formerly it was used in food processing and food handling 

establishments, but these uses have been cancelled. 

There are several hypochlorite active ingredients used in swimming pools including calcium, 

potassium and sodium hypochlorites. All of these compounds release hypochlorous acid which 

shows pesticidal action by reacting with organic and inorganic substances in the water. 

According to one of the manufacturers of this chemical, lithium hypochlorite is used in less than 

one percent of the pools in the USA.

1.1 Case Overview

The docket for the lithium hypochlorite Case (3084) was established at 

http://www.regulations.gov in docket number EPA-HQ-OPP-2013-0606. 

1.2 Use Characterization

Lithium hypochlorite is a granular chlorine product exclusively used to help control algae growth 

and sanitize swimming pools, hot tubs, and spas. Product labels recommend swimming pools 

maintain a 1-3 ppm chlorine residual. Application intervals vary from daily to weekly depending 

on the frequency of pool use, pool size, and environmental conditions. 

2.0 ENVIRONMENTAL FATE ASSESSMENT

Lithium hypochlorite forms lithium ions and hypochlorous acid when dissolved in water. 

Therefore, lithium hypochlorite can be considered a delivery system/precursor to hypochlorous 

acid and its environmental fate is essentially that of hypochlorous acid. 

Lithium is highly reactive and naturally found as complexes with other chemical constituents. 

Ionized lithium reacts rapidly with compounds in the environment to form metallic salts such as 

lithium hydroxide, lithium carbonate, lithium nitride, and lithium chloride. Lithium reacts with 

fresh water to form lithium hydroxide, while lithium chloride is the form most often found in 

seawater. Once formed, these salts are expected to be stable. 

Hypochlorous acid is a weak acid with a pKa of 7.4 at 25o C. In acidic pH media the predominate 

species is hypochlorous acid, at neutral pH both hypochlorous acid and hypochlorite ions are 

present, while at basic pH the acid dissociates to form hypochlorite ions. The mechanisms and 

rates of decomposition depend on pH, concentration, sunlight and temperature. Hypochlorous 

acid has a half-life of 1.3 to 5 hours (EPA, 1999). The rate of decomposition is greatly increased 

by direct sunlight resulting in a half-life of 2 hours or less (Lowry, 2012). These species absorb 

light between 292 and 380 nm. The concentration of organic material in the water enhances the 

rate of decomposition, but this rate of decomposition is pH dependent with the maximum 

degradation occurring at pH 6.9. For swimming pool sanitation it is recommended that the pH be 

maintained between 7.2 and 7.6, where hypochlorous acid predominates together with 

hypochlorite anions. 
6

3.0 HUMAN HEALTH RISK ASSESSMENT

3.1 Human Health Hazard

The primary toxicological consideration is the effect from exposure to the lithium ion that is 

produced from the reaction of lithium hypochlorite with water produces hypochlorous acid and 

lithium ions. Hypochlorous acid (which is an oxidizing agent and the chemical species showing 

pesticidal activity) acts by oxidizing organic and inorganic chemical contaminants. As 

hypochlorous acid exerts its oxidizing effect, the chlorine reduces to chloride ions. Thus the endproducts of lithium hypochlorite are chloride and lithium ions, both ubiquitous in the 

environment, and adverse effects from the incremental lithium hypochlorite contribution are not 

expected. Therefore this chemical is being evaluated qualitatively and toxicological endpoints 

have not been set.

The average background level of lithium in human serum has been reported as 0.014 mg/L which 

comes primarily from the natural content of lithium in food and drinking water (MRID 

41367401). It has been estimated that the natural sources of lithium provide 2.3-4.9 mg/day of 

lithium. Lithium carbonate has been used as a human drug since about 1970. The intake levels 

are 179 to 282 mg/day of lithium ion and they provide about 4.16 to 8.33 mg/L of lithium in the 

serum (MRID 41367401). For the therapeutic use, the reported maximum no-toxicity levels are 

10.41 to 13.88 mg/L in serum. These levels are far higher than the background levels and higher 

than any expected from pesticide use of lithium hypochlorite. In addition, lithium orotate and 

lithium aspartate salts are sold as over-the-counter mineral supplements that provide about 5 mg 

of lithium per daily dose. Clinical and epidemiologic studies on human use of lithium-containing 

drugs, including chronic use, have not shown any reason for concern over continued human 

exposure to lithium in at the low levels of exposure expected during the pesticidal use scenario. 

The Hazard and Science Policy Council (HASPOC) assessed the need for acute neurotoxicity, 

subchronic neurotoxicity, immunotoxicity, chronic toxicity, carcinogenicity, and reproduction 

and fertility studies during a December 12, 2013 meeting (TXR# 0056855). Based on a WOE 

approach considering all the available hazard and exposure information for lithium hypochlorite, 

the HASPOC concludes that the acute/subchronic neurotoxicity, immunotoxicity, 

chronic/cancer, subchronic inhalation, and reproduction and fertility data are not required.

Information on the effects to humans exposed to lithium not by natural sources or by therapeutic 

treatment is also available. One study looked at the levels of lithium in the urine of people who 

had been swimming in pools treated with lithium hypochlorite. No indication was found that 

these exposures led to significant lithium absorption (MRID 00037615). A controlled study on 

dermal absorption was conducted with humans who bathed in spas containing lithium chloride in 

the water. The subjects were exposed to solutions containing 40 to 45 ppm lithium ion for 20 

minutes/day, 4 days/week for two weeks. Lithium levels in the serum of the bathers were not 

increased above normal serum levels (MRID 40746701). This study demonstrates that there is no 

significant absorption of lithium through intact human skin. The EPA conducted an ethics review 

of both studies and found them to be acceptable. Without significant absorption, there would not 

be intake or accumulation of lithium in the body by this route and thus, no reason for particular 

concern about long term dermal exposure in spas and swimming pools. There is no indication 

that intake by accidental drinking of water while swimming would increase the serum level of 
7

lithium nor increase intake over that ingested in ordinary food and drink. Any intake in pools is 

not significant compared to the levels ingested in drug use.

3.2 Dietary Assessment

There are no food uses for lithium hypochlorite and therefore the EPA did not conduct a dietary 

risk assessment.

3.3 Residential Assessment

A residential exposure assessment is required for an active ingredient if (1) certain toxicological 

criteria are triggered and (2) there is potential exposure to handlers (applicators) during use or to 

persons entering treated sites after application is complete. For lithium hypochlorite, there is 

potential exposure to residential handlers and to persons entering treated sites, however, the 

toxicological criteria are not triggered and no subchronic toxicity endpoints are available to 

develop a quantitative risk assessment. Therefore, residential risk assessments are not required. 

3.4 Aggregate and Cumulative Exposure

Because there are no toxicological endpoints for lithium hypochlorite, aggregate and cumulative 

exposures do not need to be assessed for registration review.

3.5 Occupational Assessment

An occupational exposure assessment is required for an active ingredient if (1) certain 

toxicological criteria are triggered and (2) there is potential exposure to handlers (mixers, 

loaders, applicators, etc.) during use or to persons entering treated sites after application is 

complete. For lithium hypochlorite, there is potential exposure to occupational handlers and to 

persons entering treated sites, however, the toxicological criteria are not triggered and no 

subchronic toxicity endpoints are available to develop a quantitative risk assessment. Therefore, 

occupational risk assessments are not required. 

3.6 Endocrine Disruptor Screening Program (EDSP)

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, 

and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and 

chronic studies that assess growth, developmental and reproductive effects in different 

taxonomic groups. As part of its reregistration decision for lithium hypochlorite, EPA reviewed 

these data and selected the most sensitive endpoints for relevant risk assessment scenarios from 

the existing hazard database. However, as required by FFDCA section 408(p), lithium 

hypochlorite is subject to the endocrine screening part of the Endocrine Disruptor Screening 

Program (EDSP).
8

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect.

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list 

of chemicals identified for EDSP screening was published on June 14, 20131 and includes some 

pesticides scheduled for registration review and chemicals found in water. Neither of these lists 

should be construed as a list of known or likely endocrine disruptors.

For further information on the status of the EDSP, the policies and procedures, the lists of 

chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit our 

website.2

4.0 ECOLOGICAL ASSESSMENT

4.1 Characterization of Ecotoxicity

Acute and chronic toxicity studies conducted in accordance with the 850 OCSPP Harmonized 

Test Guidelines have been submitted by registrants to support registration of lithium 

hypochlorite. All available lithium hypochlorite ecotoxicity endpoints from studies submitted by 

registrants are tabulated and referenced in the Ecological Effects Profile (Appendix A). These 

data characterize lithium hypochlorite as being moderately to highly toxic to aquatic organisms 

(48-h EC50 or 96-h LC50s = 200 to 2500 μg ai/L). Lithium hypochlorite is only slightly to 

practically nontoxic to birds (LD50 = 567 mg ai/kg-bw; LC50s >5000 ppm). 

The toxic action of lithium hypochlorite in water is largely due to the hypochlorous acid formed 

when lithium hypochlorite reacts with water and dissociates into free residual chlorine and 

lithium (EPA 1993). Relevant ecotoxicity data for chlorine are available in the EPA Office of 

Water’s Ambient Water Quality Criteria for Chlorine - 1984 (AWQC; EPA 1985) and are 

summarized in Appendix A. The data characterize chlorine residues (TRC or CPO3 as being 

very highly toxic to aquatic organisms (freshwater fish 96-h LC50s >40 μg TRC/L; 

 1 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals.

2 http://www.epa.gov/endo/

3 In accordance with the AWQC (EPA 1985), the term total residual chlorine (TRC) refers to the sum of free 

chlorine and combined chlorine in fresh water and chlorine-produced oxidants (CPO) refers to the sum of these 

products in salt water.
9

estuarine/marine fish 96-h LC50s >32 μg CPO/L; freshwater invertebrate 48-h EC50s >17 μg 

TRC/L; estuarine/marine invertebrate 48-h EC50s >26 μg CPO/L). Green algae EC50s of 260 

μg/L and 983 μg/L are cited in EPA’s ECOTOX database4.

The agency has not required any additional ecotoxicity data for lithium (EPA 2014). The 

available information indicates that lithium hypochlorite toxicity to aquatic organisms is 

predominantly due to the chlorine released when lithium hypochlorite dissociates in water. The 

comparative data tabulated in Appendix A indicate that lithium hypochlorite is no more toxic to 

fish and aquatic invertebrates than is chlorine alone or are other hypochlorites (sodium or 

calcium salts), indicating that the lithium component of lithium hypochlorite contributes little to 

the overall acute toxicity. Data for LiCl in the open literature (Hamilton 1995, Long et al. 1998) 

categorize this lithium salt as being only slightly to practically nontoxic to fish and water fleas 

exposed for 48 to 96 hours (see Appendix A). 

4.2 Characterization of Exposure

Typically the Agency would use a standard model to determine the Estimated Environmental 

Concentrations (EECs) of the pesticide in the water receiving the discharge from the application 

site, however the Agency does not currently have a model to provide quantitative EECs for the 

application of pesticides to swimming pools and spas. Therefore this analysis is based on a 

qualitative assessment.

There are four pathways pool or spa water may travel once discharged: (1) onto the surface of 

the land (2) into a neighboring lake or stream (3) into the municipal sewage system or (4) into 

storm water drains. Most commonly, pools are drained directly onto the area immediately 

surrounding the pool or into municipal sewage systems. Both scenarios limit the exposure of the 

free residual chlorine, as soil naturally traps and removes impurities (i.e., chlorine) from water, 

and municipal sewage systems dechlorinate water before returning it back into the environment. 

Draining pools into a neighboring body of water or a storm drain is prohibited by many 

municipalities and discharge from waste water treatment plants is subject to National Pollutant 

Discharge Elimination System (NPDES) permits. The NPDES permit program controls water 

pollution by regulating point sources that discharge pollutants into waters of the US. If pool 

water were discharged into a neighboring body of water or storm drain, the reactivity of 

hypochlorite ions with organic matter encountered during its pathway to a natural body of water, 

as well as the organic matter in the receiving body of water, would greatly reduce hypochlorite 

exposure to aquatic organisms.

According to one of the manufacturers, lithium hypochlorite is used in less than one percent of 

the pools in the USA due to relative costs associated with the product. Also, swimming pools are 

not drained and refilled frequently. At most, it is expected that pools are drained twice a year, 

while hot tubs and spas may be drained and refilled three or four times a year. Exposure from 

these use patterns is expected to be small.

It is worth noting that free residual chlorine levels may come from several different sources 

(lithium/sodium/calcium/potassium hypochlorites, chlorinate isocyanurates, and chlorine gas), 

since all of these form hypochlorous acid in water. Thus, in cases where free residual chlorine 

 4 http://cfpub.epa.gov/ecotox/quick_query.htm
10

levels exceed permissible levels, it may be difficult to trace the source of contamination 

considering that the counter cations (lithium, sodium, calcium, and potassium) are ubiquitous in 

nature.

Based on the reasons discussed above, the Agency believes that free residual chlorine originating 

from lithium hypochlorite treated pool water under most circumstances will not significantly 

contribute to existing chlorine in the environment. The discharge of pool water is not expected to 

disrupt wastewater treatment facilities or unacceptable adverse effects to aquatic and terrestrial 

organisms due to its extremely low use compared to other inputs.

4.3 Risk Characterization

The Agency believes that there may be conditions under which treated water discharged from 

pools or spas could pose risks of concern to aquatic organisms (such as discharge of pool or spa 

waters directly into surface waters or storm drains). The main source of concern is likely to be 

acute exposure to chlorine residues. Based on the available ecotoxicity information, lithium is 

not expected to contribute significantly to the toxicity. However, because chlorine is very highly 

acutely toxic to aquatic organisms, even brief exposure to low aquatic concentrations of chlorine 

residues might have adverse effects. The EPA Office of Water has proposed freshwater and 

estuarine/marine acute criteria values in the Ambient Water Quality Criteria for Chlorine – 1984

(EPA 1985). If the one-hour average freshwater concentration exceeds 19 μg/L more than once 

every three years on the average, freshwater organisms may be unacceptably affected. 

Estuarine/marine organisms may be unacceptably affected if the one-hour average 

estuarine/marine concentration exceeds 13 μg/L more than once every three years on the 

average. The toxicity data upon which these criteria were developed are discussed in Appendix 

A. 

Chronic exposure to chlorine of aquatic organisms is not anticipated. Chlorine dissipates rapidly 

in water. Any residues reaching surface waters also will be diluted by the receiving water, 

especially flowing water (e. g., streams, creeks, tides, currents). Moreover, pool or spa water is 

discharged infrequently (EPA 1993), so residues are not likely to accumulate or persist. 

Minimal risks to birds are expected. Potential exposure would be via ingestion of aquatic prey 

that has accumulated residues. However, lithium hypochlorite is practically nontoxic to birds 

(LC50s >5000 ppm) when consumed in food, and neither chlorine nor lithium is expected to 

bioaccumulate in aquatic organisms (EPA 1985, 1993).

Whether or not chlorine residues from discharge waters reach surface waters likely depends on 

where the pool or spa water is discharged. Discharge directly into surface waters or into storm 

drains is likely to expose aquatic organisms to chlorine residues that are potentially harmful. 

However, exposure can be prevented or minimized if appropriate disposal measures are 

undertaken as described below.

Best Management Practices

Providing that an appropriate method of discharge of treated water is utilized, little if any risk of 

aquatic organisms should occur. Product labels for lithium hypochlorite do not currently prohibit 

discharge of pool or spa waters directly into surface waters or storm drains, although such 
11

practices are prohibited by some local authorities (e. g., State of Oregon Department of 

Environmental Quality5, Arlington County, VA6, California Department of Fish & Game7, 

District of Columbia Department of the Environment8

). Product labels could be revised to 

mandate that any of the following management practices must be employed when discharging 

waters to ensure that exposure of aquatic organisms is minimized.

- Discharge treated waters into municipal sewage systems

- Hold treated water in pool or spa for a minimum of 1-2 weeks before discharging to 

allow chlorine content to dissipate

- If holding times are not feasible, pool water must be chemically dechlorinated prior to 

discharge from pool or spa to ensure that the AWQC criterion value of 13 μg/L (.013 

ppm) is not exceeded, which would be protective for both estuarine/marine and 

freshwater environments 

- Do not discharge treated pool or spa water onto vegetated land immediately adjacent to 

surface waters or onto sloping land where runoff may occur into surface waters

4.4 Listed Species of Concern

Consistent with EPA’s responsibility under the Endangered Species Act (ESA), the Agency will 

evaluate risks to federally listed threatened and endangered (listed) species from registered uses 

of pesticides in accordance with the Joint Interim Approaches developed to implement the 

recommendations of the April 2013 National Academy of Sciences (NAS) report, Assessing 

Risks to Endangered and Threatened Species from Pesticides. The NAS report9 outlines

recommendations on specific scientific and technical issues related to the development of 

pesticide risk assessments that EPA and the Services must conduct in connection with their 

obligations under the ESA and FIFRA. EPA will address concerns specific to lithium 

hypochlorite in connection with the development of its final registration review decision for 

lithium hypochlorite.

In November 2013, EPA, the U.S. Fish and Wildlife Service, National Marine Fisheries (the 

Services), and USDA released a white paper containing a summary of their joint Interim 

Approaches for assessing risks to listed species from pesticides. These Interim Approaches were 

developed jointly by the agencies in response to the NAS recommendations, and reflect a 

common approach to risk assessment shared by the agencies as a way of addressing scientific 

differences between the EPA and the Services. Details of the joint Interim Approaches are 

contained in the November 1, 2013 white paper10, Interim Approaches for National-Level 

Pesticide Endangered Species Act Assessments Based on the Recommendations of the National 

Academy of Sciences April 2013 Report.

 5 Fact Sheet – Disposing of Chlorinated Water from Swimming Pools and Hot Tubs, April, 2014, 

http://www.deq.state.or.us/wq/pubs/factsheets/wastewater/bmpchlorwaterdisp.pdf

6 Draining Swimming pool Water Safely, July, 2015, https://water.arlingtonva.us/environment/swimming-pools/ 7 Guidelines for Proper Disposal of Swimming Pool, Spa & Filter Backwash Water, http://www.sonomacounty.org/health/services/pdf/pool_guidelines.pdf

8 http://ddoe.dc.gov/service/how-drain-your-swimming-pool-properly 9 http://www.nap.edu/catalog.php?record_id=18344

10 http://www.epa.gov/espp/2013/nas.html
12

Given that the agencies are continuing to develop and work toward implementation of the 

Interim Approaches to assess the potential risks of pesticides to listed species and their 

designated critical habitat, this ecological risk assessment supporting the registration review of 

lithium hypochlorite does not describe the specific ESA analysis, including effects 

determinations for specific listed species or designated critical habitat, to be conducted during 

registration review. While the agencies continue to develop a common method for ESA analysis, 

the risk assessment for the registration review of lithium hypochlorite describes only the level of 

ESA analysis completed at this time. This assessment allows EPA to focus its future evaluations 

on the types of species where the potential for effects exists, once the scientific methods being 

developed by the agencies have been fully vetted. Once the agencies have fully developed and 

implemented the scientific methods necessary to complete risk assessments for listed species and 

their designated critical habitats, these methods will be applied to subsequent analyses of lithium 

hypochlorite as part of completing this registration review.
13

5.0 REFERENCES

00037615 Nelli, J.R. (1964) The Build-Up of Lithium Ion in Swimming Pool Waters and Its 

Effect on Swimmers. (Unpublished study received Oct 30, 1964 under 7675-1; submitted 

by Lithium Corp. of America, Gastonia, N.C.; CDL:050685-A)

40746701 McCarty, J.; Carter, S.; Fletcher, M.; et al. (1988) Study of Lithium Absorption by 

Users of Spas Treated with Lithium Ion: Study No. I87-0981. Unpublished study 

prepared by FMC Toxicology Dept. 225 p.

41367401 Todhunter, J.; Mandava, N. (1990) Supplemental Data and Documentation in Support 

of Data Waiver Requests filed by Lithium Corporation of America dated November 24, 

1989: FMC Study No. I90-1108. Unpublished study prepared by SRS International. 1424 

p.

Dvorakova, D., R. Rojickova-Padrtova and B. Marsalek. 1999. Is the replacement of 

Scenedesmus quadricauda L. by Selenastrum capricornutum L. in toxicity tests 

reasonable? Pol. Arch. Hydrobiol. 46:345-352.

EPA 1985. Ambient Water Quality Criteria for Chlorine - 1984. Office of Water Regulations 

and Standards Criteria and Standards Division, EPA 440/5-84-030.

EPA 1993. Lithium Hypochlorite Reregistration Eligibility Decision (RED). EPA 738-R-93-023, 

December, 1993.

EPA 2014. Lithium Hypochlorite Preliminary Work Plan. Registration Review: Initial Docket, 

Case No. 3084, EPA-HQ-OPP-2013-0606, March, 2014.

EPA 2014. Lithium Hypochlorite: Summary of Hazard and Science Policy Council (HASPOC) 

Meeting of December 12, 2013: Recommendations on the Need for Acute 

Neurotoxicity/Subchronic Neurotoxicity Studies, Immunotoxicity, Chronic/cancer, 

Subchronic inhalation, and Reproduction and fertility. Office of Pesticide Programs, 

January 27, 2014, TXR# 0056855

Hamilton, S.J. 1995. Hazard assessment of inorganics o three endangered fish in the Green 

River, Utah. Ecotox. Environ. Safety 30:134-142.

Long, K.E., R.P. Brown, Jr. and K.B. Woodburn. 1998. Lithium chloride: a flow-through 

embryo-larval toxicity test

Lowry Robert. Lowry Consulting Group, 2012, http://www.lowrycg.com/wpcontent/uploads/2013/05/Cyanuric-Acid-It-Controls-Your-Pool-rev03.pdf
14

APPENDIX A: Summary of Ecotoxicity Data 

Lithium hypochlorite (LiOCl)

Toxicity to Aquatic Organisms

Freshwater Fish 

The available acute toxicity studies categorize lithium hypochlorite as being moderately to 

highly toxic to freshwater fish. 

Acute Toxicity to Freshwater Fish

Test Species Test Material

(% ai)

Toxicity Endpoint

(μg ai/L)

Toxicity

Category

EPA Study

ID

Rainbow Trout

(Oncorhynchus mykiss) 29 96-hr LC50 = 200 Highly toxic 00094672Acceptable

15 96-hr LC50 = 2500 Moderately toxic 00007302

Supplemental

Bluegill

(Lepomis macrochirus) 29 96-hr LC50 = 280 Highly toxic 00094672

Acceptable

15 96-hr LC50 = 6170 Moderately toxic 00007302

Supplemental

Freshwater Invertebrates

The acute toxicity study for the waterflea categorizes lithium hypochlorite as being very highly 

toxic to freshwater invertebrates. 

Toxicity to Freshwater Invertebrates

Test Species Test Material

(% ai)

Toxicity Endpoint

(μg ai/L)

Toxicity

Category

EPA Study

ID

Waterflea

(Daphnia magna) 29 48-hr EC50 = 230 Highly toxic

00094674

Acceptable

Aquatic Plants 

No data are available for lithium hypochlorite. Green algae data are available for hypochlorous 

acid (see Chlorine section below for data).
15

Toxicity to Terrestrial Organisms

Birds

Lithium hypochlorite is slightly toxic to birds when administered orally via gavage but is 

practically nontoxic when administered in the diet. 

Avian Acute-oral and Dietary Toxicity

Test Species Test Material

(% ai) Toxicity ToxicityCategory

EPA Study

ID

Mallard

(Anas platyrhynchos)

29 LD50 = 567 mg ai/kg bw Slightly toxic 00094673

Acceptable

29 LC50 >5000 ppm Practically nontoxic 00104674

Acceptable

15 LC50 >10,000 ppm Practically nontoxic 00104674

Supplemental

Northern bobwhite

(Colinus virginianus)

29 LC50 >5000 ppm Practically nontoxic 00104674

Acceptable

15 LC50 >10,000 ppm Practically nontoxic 00104674

Supplemental

Chlorine

Data on the toxicity of chlorine residues to aquatic organisms are available in the EPA Office of 

Water’s Ambient Water Quality Criteria for Chlorine - 1984 (EPA 1985). That document 

provides ecotoxicity endpoints from the open literature to address the available acute and chronic 

toxicity to freshwater and estuarine/marine organisms. Because various forms of chlorine 

(hypochlorous acid, hypochlorite ion, monochloramine, dichloramine) may be formed in 

freshwater, the term total residual chlorine (TRC) is used to refer to the sum of free and 

combined chlorine in freshwater. Salt water contains bromine and addition of chlorine also 

produces hypobromous acid, hypobromous ion, and bromamines. Chlorine-produced oxidants 

(CPO) refers to the sum of these products in salt water.

Toxicity to Freshwater Fish and Invertebrates

The AWQC provides endpoints for 33 species in 28 genera. The acute endpoints characterize 

TRC as being highly to very highly toxic to freshwater organisms, with fish and invertebrates 

having a similar range of sensitivity. Acute toxicity values (EC50 or LC50) for invertebrates 

range from 17 μg TRC/L for Daphnia magna to 960 μg TRC/L for a crayfish (Orconectea nals). 

For fish, acute values range from 40 μg TRC/L for rainbow trout (Oncorhynchus mykiss) to 710 

μg TRC/L for the threespine stickleback (Gasterosteus aculeatus). Chronic values were 

provided for one fish species and two invertebrate species. Chronic effects were reported in the 

range of 2-7 μg TRC/L for D. magna and 6-21 μg TRC/L for the fathead minnow (Pimephales 

promelas).
16

The AWQC document established numerical water quality criteria for protection of aquatic 

organisms. For freshwater organisms, except possibly where a locally important species is very 

sensitive, the Criterion Maximum Concentration (CMC) should be protective if the value does 

not exceeded he four-day average concentration more than once every 3 years on the average. 

The Criterion Continuous Concentration (CCC) should be protective if the 1-hour average 

concentration does not exceed the value more than once every 3 years on the average. The 

current values are as follows:

• Freshwater CMC = 19 μg/L

• Freshwater CCC = 11 μg/L

Toxicity to Salt water Fish and Invertebrates

The acute sensitivity was determined for 24 species in 21 genera, and sensitivities were 

comparable to those for freshwater species. Invertebrate acute values range from 26 μg CPO/L 

for the Eastern oyster (Crassostrea virginica) to 1418 μg CPO/L for a crayfish (Orconectea 

nals). Fish acute values range from 32 μg CPO/L for coho salmon (Oncorhynchus kisutch) to 

270 μg CPO/L for the northern pipefish (Syngnathus fuscus). Based on one fish study with the 

tidewater silverside (Menidia peninsulae), chronic effects were observed at 40-54 μg CPO/L.

Using the same criteria as for freshwater, the current criteria for salt water organisms are as 

follows:

• Salt water CMC = 13 μg/L

• Salt water CCC = 7.5 μg/L

Toxicity to Aquatic Plants

Toxicity values are not provided, but the AWQC notes that exposure to TRC concentrations less 

than 1000 μg/L for periods of one hour or less can reduce survival and inhibit physiological 

processes. However, algal populations seem to be able to recover from initial effects of short 

exposure. Brief exposure to CPO did not cause substantial long-term damage to phytoplankton 

assemblages in several studies. The AWQC concludes that the available data indicate that 

aquatic plants appear to be less sensitive to chlorine exposure than do fish or aquatic 

invertebrates.

The ECOTOX database11 contains toxicity data from Dvorakova et al. (1999) for two species of 

green algae exposed to hypochlorous acid (calcium salt). Reported toxicity values for effects on 

 11 The ECOTOXicology database (ECOTOX) is a source for locating single chemical toxicity data for aquatic life, 

terrestrial plants and wildlife. ECOTOX was created and is maintained by the U.S.EPA, Office of Research and 

Development (ORD), and the National Health and Environmental Effects Research Laboratory's (NHEERL's) MidContinent Ecology Division (MED). http://cfpub.epa.gov/ecotox/
17

population growth rate are EC50 = 260 μg/L for Scenedesmus quadricauda and EC50 = 983 

μg/L for Pseudokirchneriella subcapitata.

Lithium

The available data indicate that the toxicity of lithium hypochlorite to fish and aquatic 

invertebrates is mainly due to chlorine (see table below). Few data on lithium toxicity to aquatic 

organisms are available, but a comparison of toxicity values of chlorine and other hypochlorites 

(Ca and Na) to that of lithium hypochlorite indicates that the lithium component adds little if any 

to the toxicity of lithium hypochlorite. 

Comparative Toxicity of Chlorine and Hypochlorites

Test species

LC50 or EC50 (μg/L)

Chlorine1 Li 

hypochlorite2

Ca 

hypochlorite3

Na 

hypochlorite3

Rainbow trout

(Oncorhynchus mykiss) 40 200 160 200

Bluegill

(Lepomis macrochirus) 180 280 86 560

Water flea

(Daphnia magna) 17 230 73 40

1

EPA 1985

2

EPA 2014

3

OPP Ecotoxicity Database

Additional information on lithium toxicity to aquatic organisms is available in studies using LiCl 

as the test material. LiCl was only slightly to practically nontoxic to three species of fish tested 

by Hamilton (1995; tabulated below). In acute tests, Long et al. (1998) found LiCl to be only 

slightly acutely toxic to fathead minnows and water fleas in 48- or 96-h tests; LiCl was slightly 

more toxic to fathead minnows exposed for 26 days.

Toxicity of LiCl to Fish and Aquatic Invertebrates

Species Toxicity

(mg/L)

Reference

Acute:

Fathead minnow 

(Pimephales promelas)

96-h LC50 = 42 Long et al. 1998

Water flea 

(D. magna)

48-h EC50 = 24

Colorado squawfish 

(Ptychocheilus lucius)

96-h LC50 = 17-41a Hamilton 1995

Razorback sucker 

(Xyrauchen texanus)

96-h LC50 = 25-186a

Bonytail 96-h LC50 = 22-65a
18

(Gila elegans)

Chronic:

Fathead minnow 26-d LC50 = 8.7

26-d NOAEC =1.2

(growth)

Long et al. 1998

a swimup fry (10-31 days old) were more sensitive than juveniles (99-234 days old; 0.24-2.6 g) 

Additional Appendix A References

94673 Piccirillo, V.J. (1977) Final Report: Acute Oral LDI50 Study in Mallard Ducks: 

Project No. 668-107. (Unpublished study received Apr 25, 1978 under 7675-4; 

prepared by Hazleton Laboratories America, Inc. and Truslow Farms, Inc., submitted 

by Lithium Corp. of America, Gastonia, N.C.; CDL:246732-D) 

104674 Piccirillo, V.J. (1977) Final Report: Subacute Dietary LCI50 Study in Bobwhite 

Quail: Project No. 668-109. (Unpublished study received Apr 25, 1978 under 7675-4; 

prepared by Hazleton Lab- oratories America, Inc. and Truslow Farms, Inc., submitted 

by Lithium Corp. of America, Gastonia, N.C.; CDL:246732-B) 

94672 Buccafusco, R.J. (1978) Acute Toxicity of Lithcoa Lithium Hypochlorite to Rainbow 

Trout (Salmo gairdneri): Report #BW-78- 2-031. (Unpublished study received Apr 

25, 1978 under 7675-4; prepared by EG & G Bionomics, submitted by Lithium Corp. 

of America, Gastonia, N.C.; CDL:246732-C) 

7302 Sleight, B.H., III (1972) Bioassay Report: Acute Toxicity of K-70 Algaecide to 

Bluegill (Lepomis macrochirus) and Rainbow Trout (Salmo gairdneri). (Unpublished 

study received Dec 12, 1972 under 5135-17; prepared by Bionomics, Inc., submitted 

by Water Services, Burbank, Calif.; CDL:132135-C) 

94674 LeBlanc, G.A. (1978) Acute Toxicity of Lithcoa Lithium Hypochlorite to the Water 

Flea (Daphnia magna): Report #BW-78-2-032. (Unpublished study received Apr 25, 

1978 under 7675-4; prepared by EG & G Bionomics, submitted by Lithium Corp. of 

America, Gastonia, N.C.; CDL:246732-E)