I:\MEPC\54\2-3.doc 

For reasons of economy, this document is printed in a limited number. Delegates are 

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INTERNATIONAL MARITIME ORGANIZATION

IMO

E

MARINE ENVIRONMENT PROTECTION 

COMMITTEE 

54th session 

Agenda item 2 

MEPC 54/2/3

 16 December 2005

 Original: ENGLISH

HARMFUL AQUATIC ORGANISMS IN BALLAST WATER 

Application for Basic Approval of Active Substances used by Electro-Clean (Electrolytic 

Disinfection) Ballast Water Management System 

Submitted by the Republic of Korea 

SUMMARY

Executive summary: This document provides an application for Basic Approval of Active 

Substances used by Electro-Clean (electrolytic disinfection) Ballast 

Water Management System in accordance with the Procedure for 

approval of Ballast Water Management Systems that make use of 

Active Substance (G9) adopted by resolution MEPC.126(53). The 

relevant documents and dossiers have been submitted to Marine 

Environment Division of the Organization for review by the 

GESAMP-Ballast Water Working Group. 

Action to be taken: Paragraph 5 

Related documents: MEPC 53/24, MEPC 53/24/Add.1 

Introduction 

1 This document provides an application for Basic Approval of Active Substances in 

accordance with the Procedure for approval of Ballast Water Management Systems that make use 

of Active Substance (G9) adopted by resolution MEPC.126(53). 

2 The relevant documents and dossiers have been submitted to Marine Environment 

Division of the Organization for review by the GESAMP-Ballast Water Working Group. 

3 The applicant is proposing a ballast water management with Electro-Clean (electrolytic 

disinfection) system. This system produces low concentration of Active Substances by 

electrolytic treatment. Due to a synergy effect of various Active Substances, it has been shown 

to effectively kill all of the organisms in ballast water. 

4 Annexed to this document is a proposal for approval of Active Substances used by 

Electro-Clean (electrolytic disinfection) system which is prepared by Techcross Ltd. and Korea 

Ocean Research and Development Institute (KORDI). 
MEPC 54/2/3 - 2 - 

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Action requested of the Committee 

5 The Committee is invited to consider the proposal for approval of the Active Substances 

used by Electro-Clean (electrolytic disinfection) system for ballast water management. 

*** 
MEPC 54/2/3 

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ANNEX 

Information for Basic Approval of Active Substances used by Electro-Clean 

(Electrolytic-Disinfection) Ballast Water Management System 

1 INTRODUCTION

In the Electro-Clean (electrolytic disinfection) technology, Active Substances including Cl2, 

HOCl, OCl- and OH radical are produced during electrolysis of seawater (1). Due to synergy 

effect of these Active Substances, the system effectively kills bacteria, yeasts, virus, moulds, 

spores, algae, protozoa, zooplankton, phytoplankton, larval stages and fish eggs in ballast 

water (2). This technology is effective at high concentration of sediment and/or organic matter at 

pH values between 5 and 9 in the temperature higher than 5oC. 

The level of Active Substances produced during electrolysis of seawater can be closely 

controlled by applying an appropriate current density (3). The Active Substances produced do 

not persist in seawater and do not create any persistent byproduct at their level. 

2 SPECIFIC CHARACTER OF ELECTRO-CLEAN (ELECTROLYTIC 

DISINFECTION) TECHNOLOGY

Safety

The equipment employs the electrodes to supply electrons which are clean reagent, so there is no 

need for storage or transportation of chemicals which ensures the operational safety and no risk 

of exposure. The Active Substances in Electro-Clean system are hypochlorite, chlorine and 

ozone which are used to disinfect drinking water (4). The levels of Active Substances produced 

during the electrolysis of seawater are below the standards for dangerous substances 

(United Statesí standards). 

Economy

The Electro-Clean system is composed of electrochemical reactor employing electrode and 

rectifiers which makes the system compact. Because there is no need for chemical storage tanks, 

the system is also economical. 

Environmental hazard

The Active Substances that are produced during disinfection are radicals and oxidative 

substances including chlorine and hypochlorite which have short life span. The Active 

Substances can be reduced by reductive substances or organisms in seawater. They are also 

degraded in nature to lower concentration. In case of natural disasters such as typhoons and 

earthquakes, cutting-off electricity alone will ensure the safety. 
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3 EFFICIENCY OF THE ELECTRO-CLEAN (ELECTROLYTIC DISINFECTION) 

SYSTEM

3.1 Principle of disinfection

.1 Disinfection by electric potential

Electric potential is the driving force which makes oxidation reaction occur at the 

anode (positive) and reduction occur at the cathode (negative) in the electrolytic 

cell. In simple terms, from a microbial perspective, an oxidizing chemical pulls 

electrons away from the cell membrane, causing it to become destabilized and 

leaky. Destroying the integrity of cell membrane leads to rapid death of organism 

in a few seconds (5). 

.2 Disinfection by free chlorine

Hypochlorite can be formed during electrolysis of saline water. Natural seawater 

contains chloride ion which is about 19.5gL-1. The presence of 0.53mol/L of 

chloride in seawater serves as an abundant source for electrochemical generation 

of chlorine and hypochlorite (6). 

At the Anode: 

2Cl-

 Cl2 + 2 eIn the Bulk: 

Cl2 + 2H2O HClO + Cl- + H3O+

HClO +H2O C lO-

 + H3O+

These two reversible reactions have the equilibrium constants of 4 x 10-4 mol/L 

and 3 x 10-8 mol/L, respectively, at 25°C (7). Hypochlorous acid is a weak acid 

and will undergo partial dissociation as follows: 

HOCl H+

 + OClIn waters of pH between 6 and 9, both hypochlorous acid and hypochlorite ion 

will be present. The proportion of each species depends on pH and temperature. 

Hypochlorous acid is significantly more effective as a biocide than the 

hypochlorite ion as hypochlorous acid destroys organisms within two seconds, 

whereas hypochlorite ion takes 25-30 minutes to do the same (8). 

.3 Disinfection by radicals

Seawater with its various salts is broken down into components according to the 

electrochemical reactions that occur on the surface of the electrodes. OH radical 

produced during electrolysis is very unstable substances and exists for only a few 

billionths of second. This radical, through the exchange of ions, instantaneously 

disinfect bacteria and aquatic micro-organisms. 
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.4 Electrochemical oxidation

Electrochemical oxidation involves direct disinfection through the exchange of 

electron with the surface of electrodes and indirect disinfection through the 

creation of oxidants such as O3 and Hydrogen peroxide. Ozone has been limitedly 

used as an alternative to chlorine because it decreases the formation of THMs in 

the water, while hydrogen peroxide is used as a disinfectant in medical application 

and as an oxidant for industrial purposes. These substances do have a little 

stability, so they will help in reducing the development and reproduction of 

micro-organisms and bacteria in ballast water (9). 

When ozone decomposes in water, the free radicals of hydrogen peroxy (HO2) and 

hydroxyl (OH) that are formed have great oxidizing capacity and play an active 

role in the disinfection process. It is generally believed that bacteria are destroyed 

because of protoplasmic oxidation resulting in cell wall disintegration (cell lysis). 

At low pH levels, ozone itself becomes the target of ozonization, resulting in 

oxidation processes with the surface layers of micro-organisms that easily react to 

ozone. At low pH levels, ozone breaks down the parts that are unsaturated bonds, 

as well parts that have a high concentration of electrodes. Therefore, ozone is 

effective in breaking down unsaturated bonds and the oxidization of molecules 

that possess nucleophilic atoms such as amino acids. At high pH levels, ozone has 

even greater oxidization capability because it becomes a reactant with the 

OH radicals that are produced when ozone reacts with water. 

3.2 Biological efficacy test of Electro-Clean system

3.2.1 Results of marine organisms

Land-based test has been conducted to assess whether the Electrochemical Disinfection System 

meets with Regulation D-2 as a suitable Ballast Water Management System (BWMS). For 

approval of testing process, test organisms smaller than 50μm and larger than or equal to 10μm

were included with 1.37×107

 cells/L in the influent water. 

Species of organisms were mainly diatoms, silicoflagellates, euglenoids, dinoflagellates, 

microflagellates in terms of phytoplankton. Test organisms larger than or equal to 50 μm in the 

test water were 4× 105 inds./m3 comprised of copepods, cladocerans, harpacticoids and larvae of 

natural organisms, including Artemia as incubated larvae. Operating conditions of electrolytic 

disinfection system were at voltages 3.6(9.8 ampere; condition 1) and 5.2(15.2 ampere, 

condition 2). 

Biological efficacy of Electro-Clean system was estimated in terms of concentration of viable 

organisms in the influent and effluent water in two different conditions. Viable organisms were 

less than 10 cells/ml in the size group smaller than 50μm and larger than or equal to 10 μm, and 

less than 10 inds./m3 in the size group larger than or equal to 50μm. Viable microbes in terms of 

E. coli and coliforms were not observed after 48-hr incubation period. 
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Effluent water being passed through the system was maintained under dark conditions to 

simulate the inside of shipís ballast tank during twenty days. Since no viable organisms were 

observed at the time of daily check-up during the experimental period, it can be concluded that 

the two experimental conditions of Electro-Clean system were in compliance with the 

regulation D-2. 

3.2.2 Results of fresh water organisms

Land-based test was conducted to assess the disinfection efficacy of the Electro-Clean 

system (10). Operating condition was 6V/15A and without the addition of electrolyte. Total 

residual chlorine was 2.5mg/L after 5 minutes. Surviving algal cells were counted based on 

fluorescence intensity with N.A binding DYE. 

No viable microbes were observed after 0.5-hour incubation period. The removal efficacy of 

testing algal species was above 90%, except for Senedesmus quadricaud, in 5 minutes. A test to 

assess the removal efficiency of plankton present in water of Dae-Chung Reservoir, a source of 

drinking water for local residents in Korea, by electrochemical disinfection system was carried 

out. The numbers of phytoplanktons were 5.0× 106

 cells/L in the testing water. Operating 

conditions was 6V/3A and residual chlorine was 0.3 mg/L after 5 minutes. Dominant 

micro-organisms were Microcystis spp, Anabaena spp. and Oscillatoria spp. Algal viability was 

reduced by 90% in 10 minutes after electrochemical disinfection. 

4 GENERAL REQUIREMENTS

4.1 Identification

Active Substances produced during electrolysis of seawater are Cl2, HOCl, OCl-

 and OH radical. 

The chlorine is hydrolyzed creating HC1 and HOCl as shown in Equation (5). HOC1 dissociates 

as shown in Equation (7). 

Cl2 + H2O HCl + HOCl -------- (1) 

HOCl H+

 + OCl- -------- (2) 

The equilibrium of this reaction depends on the temperature and pH of the water, and the 

chlorine takes on three forms: molecular chlorine, hypochlorous acid and hypochlorite ion. All 

of these are residual chlorine (11). 

In water above pH 4, the concentration of molecular chlorine is less than 1~2% while almost all 

the rest is HOCl. At pH 7, about 75% is HOCl and 25% OCl-

. At pH 8 and pH 9, 75% and 95% 

exists as OCl- respectively. Because HOCl and OCl- share similar properties, Cl2, OCl-, 

OH radicals and ORP potential which have significant influence on disinfection will be 

discussed. 
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4.2 Data on Active Substances

4.2.1 Data on hypochlorite

4.2.1.1 Data on effects of hypochlorite on aquatic organisms:

4.2.1.1.1 Lethal concentrations (LC99, IC99) of hypochlorite for freshwater and saltwater 

Biota:

Table 1: Lethal concentration range of hypochlorite for fresh water and salt water 

Lethal 

Concentration 

Range (mg/L) 

Fresh water Salt water 

<1 

Alga S. capricornutum (48 hr) 

Alga ñ Nanochloris sp. (48 hr) 

Alga ñ S. obliquus (48 hr) 

Invertebrate ñ D. magna (neonate) (48 hr) 

Bacteria ñ V.fischeri (15 min) 

Alga ñ S.costatum (48 hr) 

1 to 10 

Bacteria ñ Bacillus subtilis (spore) (48 hr) 

Mollusc ñ D.polymorpha (veliger) (24 hr) 

Benthic invertebrate ñ L.variegates (48 hr) 

Fish ñ C.caprio (48 hr) 

Amphipod ñ E.estuaris (48 hr) 

Fish ñ C.variegatus (48 hr) 

10 to 100 Invertebrate ñ D.magna(ephippia) (48hr) 

100 to 1,000 Invertebrate ñ A. salina (cyst) (24 hr) 

For the fresh water species, algae (including S. capricornutum, S. obliquus, and Nanochloris sp.) 

exhibited the lowest tolerance to hypochlorite (IC99s 0.1 mg/L), followed by D. magna 

(LC99 = 0.2 mg/L based on exposure of neonates (< 24-h old)). The most tolerant species, based 

on exposure of the resting egg or ìephippiaî, was D. magna (IC99 = 76.3 mg/L). Lethal effect 

levels for all other species were in between this range with LC99s below 10 mg/L. 

For the salt water species, the bacterium (Vibrio fischeri) and the alga (S. costatum) exhibited the 

lowest tolerance to hypochlorite with IC99 estimated to be 0.15 and 0.20 mg/L, respectively. 

The most tolerant species was the brine shrimp (A. salina), based on exposure of the cyst 

(IC99 486 mg/L). All other species were in this range with IC/LC 99s below 10 mg/L. 

Toxicity tests using selected organisms were conducted to assess the relative toxicity of sodium 

hypochlorite in dilution water versus ballast water. The results of the toxicity tests are presented 

in the table given below. 

Table 2: Comparison of hypochlorite toxicity to Lumbriculus variegatus and Eohaustorius 

estuarius in dilution waters versus ballast waters 

Species Fresh water (48 hr) Salt water (48 hr)

Laboratory Water 

LC99 (TRC mg/L) 

Ballast Water 

LC99 (TRC mg/L) 

Laboratory Water 

LC99 (TRC mg/L) 

Ballast Water 

LC99 (TRC mg/L) 

L. variegatus 1.485 (1.410-1.508) 0.743(0.743-0.743) --- --- 

E. estuarius --- --- 6.998 (3.728-7.245) 7.448 (7.448-7.448)
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The tests conducted with the L. variegatus suggested that hypochlorite was more toxic in ballast 

water (LC99 = 0.743 mg/L) relative to the dilution water (LC99 = 1.485 mg/L). But in the tests 

with E. estuaries, results indicate hypochlorite is slightly more toxic in the dilution water than 

ballast water. 

4.2.1.1.2 Reproduction of sodium hypochlorite for aquatic organisms

Acute toxicity (after 24 hrs) of sodium hypochlorite (NaClO) to newborn individuals of daphnia 

is reported in the literature. On the base of these results, NOEC has been determined as the 

concentrations causing death rate lower than 20%, showing no significant differences with 

control NOEC for NaClO is 0.031 mg/l. NaClO at NOEC concentration (0.031 mg/l) caused 

decrease in females survival (to 63%), decrease in young survival (to 0%) and decrease in 

reproduction rate (from 36.9 to 28.4 young/female) (12). NOEC of sodium hypochlorite for 

opossum shrimp was reported as 0.087mg/L (13, 14). 

4.2.1.2 Data on effect of hypochlorite on mammalian 

4.2.1.2.1 Toxic effect on human 

4.2.1.2.1.1 Short-term (acute) exposure

Inhalation

Hypochlorite does not easily form into vapour. The amount of chlorine released from dilute 

solution of hypochlorite solutions (less than 5.25%) under normal condition therefore is not 

significant. However, with more concentrated solutions and if the pH is powered, or if the 

solution is heated or if mixed with acids, higher amount of chlorine may be released. Mists 

formed from solutions can cause mild to severe irritation of the nose and throat, depending 

mainly upon the airborne concentration and the strength of the solution. There is no information 

about the short-term inhalation exposure to mists from hypochlorite solutions for human 

or animal. 

Skin contact

Hypochlorite solutions can cause mild irritation to corrosive injury depending on the duration of 

contact, the concentration and pH of the solution, based on human and animal information. 

No irritation was experienced by 20 volunteers following the application of 1% hypochlorite 

solution (pH unspecified) for 48 hours in the form of a covered patch. When 2% solution 

(pH unspecified) was used, weak or moderate irritation was experienced by 15 out 

of 69 volunteers (15). No skin reaction was observed in 3 volunteers following a 48-hour 

application of 0.252% solutions in the form of a covered patch (16). Severe irritation was 

experienced by volunteers after 4-hour application of 5.25% hypochlorite solution (pH 10.7) to 

unbroken skin in the form of a covered patch (17). Slight redness and small wheals (hives) were 

observed in 4 out of 10 volunteers within 20 minutes of application of 0.1 ml of 6% sodium 

hypochlorite solution (pH 11.2) to the forehead (17). 

Eye contact

Hypochlorite solutions can cause mild irritation to corrosive injury, depending on the 

concentration and pH of the solution, and the duration of the contact, based on human and animal 

information. There are several reports of pain, and in some cases, slight damage to the surface of 
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the eye and/or cornea, being experienced after direct contact with commercial products 

containing sodium hypochlorite (approximately 5%). The eyes were washed with water or a salt 

solution (saline) and the injury cleared within 1-2 days (18, 19, 20). There are 3 reports of 

burning to the eyes with slow recovery following exposure to concentrated solutions 

(concentration unspecified) (21). Sodium hypochlorite solutions decompose into chlorine gas 

slowly on contact with air. If mixed with acids or warmed to higher temperatures, significant 

concentrations of the gas are released. Chlorine gas is severe eye irritant. Stinging, burning 

sensation, rapid blinking, redness and watering of the eyes have been observed at chlorine 

concentrations of 1mg/L and higher. 

Ingestion

Swallowing hypochlorite solutions can cause irritation, pain and inflammation of the mouth, 

throat and stomach, as well as vomiting. In severe cases, serious effects including ulceration and 

perforation of the gastrointestinal tract and death can result (21, 22, 23). The effects depend on 

several factors, e.g., the amount ingested, the concentration and pH of the solution (21). 

About 29.5ml of a solution with 15% available chlorine may be lethal (21). For sodium 

hypochlorite solution with 3-6% of available chlorine, a lethal dose for humans of 200 ml has 

been reported (18). Severe injury has been observed in a person who ingested approximately 1 litre 

of 5.25% sodium hypochlorite having pH of 10.8(24). A woman who intentionally swallowed 

approximately 700ml of 5.25% sodium hypochlorite having pH of 11.5, showed falling mental 

status, perforation of the stomach, and died of cardiac arrest 4.5 hours after ingestion (23). 

Deaths have also resulted from aspiration of sodium hypochlorite solution into the lungs (18). 

4.2.1.2.1.2 Long-term (chronic) exposure

Skin

Prolonged or repeated contact with hypochlorite may cause dry, red, cracked skin (dermatitis). 

In a 5-year survey, 17/130 (13.1%) of first-time attacks of dermatitis reported among chemical 

factory workers were attributed to the misuse of hypochlorite to the clear skin (frequency of use 

and concentration not reported) (25). 

Skin sensitization

It is not possible to conclude hypochlorite as an occupational skin sensitizer. A few cases of skin 

sensitization have been reported, in all but one case, the individuals were predisposed to this type 

of reaction (reacting to other common allergens as well) (15, 16, 17). Two non-occupational 

cases of sensitization to sodium hypochlorite have been confirmed by patch tests. Both 

individuals reported a history of skin reactions following exposures to products containing 

sodium hypochlorite or chlorine. Other family or personal history of allergies has not been 

reported (26, 27). Negative results (0/86 and 0/90 individuals sensitized) have been obtained in 

two unpublished sensitization tests on human volunteers (human repeated insult patch test) 

using 4% sodium hypochlorite solution (18). 

Carcinogenicity 

The International Agency for Research on Cancer (IARC) has concluded that hypochlorite is not 

classifiable as to its carcinogenicity to humans. 
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Teratogenicity and embryo toxicity

No specific conclusions can be drawn about the potential developmental toxicity of sodium 

hypochlorite from a human population study that examined the potential effects of chlorinating 

drinking water with sodium hypochlorite. Exposure in this study was based on the chlorination 

method, and not the measured amount of sodium hypochlorite or its byproducts in the water (28). 

Reproductive toxicity

There is no human information available for reproductive toxicity. No firm conclusion can be 

drawn based on the limited animal information available. 

Mutagenicity

There is no information available for human. The available information for animal suggests that 

sodium hypochlorite is not mutagenic. A positive result (sperm-head abnormalities) was 

obtained in one test using live mice. This test did not directly measure genetic damage. 

Negative results have been obtained in other tests with live mice. 

Potential for accumulation

Hypochlorite does not accumulate in the body. It reacts with tissues (21). A rat study using 

radiolabelled hypochlorous acid has shown that it is absorbed fairly rapidly in serum and 

eliminated from plasma with a half-life of 44 hours. 

4.2.1.2.2 Toxicological information on other mammals

4.2.1.2.2.1 Short-term (acute) exposure

Ingestion

Vomiting has been observed in dogs following ingestion of 5 ml of 5.25% sodium hypochlorite 

(18). Extensive damage to the stomach, esophagus and small intestine were observed in a dog, 

which died after ingesting 100 ml of a 5.25% solution, having pH of 10.8 (29). 

Eye irritation

No irritation was observed in rabbits following application of a 0.005% or 0.005% solution. 

Application of a 0.5% solution produced swollen and bloodshot eyelid at 2 and 6 hours. The 

animals returned to normal condition within 4 hours (18). In another study, application of 

a 5% solution produced moderate to severe irritation in rabbits. Immediate pain was experienced 

by rabbits by application of a 5% solution (pH 11.1-11.6). When eyes were rinsed with water 

within 30 seconds, effects were not severe (slight effects on the cornea and swelling of the inner 

eyelids) and the effect lasted for less than one day. When the solution was not rinsed away, the 

injury was more severe (swollen and bloodshot eyes), but cured within a week (19). Severe 

irritation (scored 61.3/110) was observed in rabbits following application of undiluted sodium 

hypochlorite (30). 

Skin irritation

Very dilute solution has caused negligible irritation, while more concentrated solutions can cause 

corrosive injury. Negligible and slight irritation was observed in rabbits by application of 0.6 
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and 0.8% solutions (18). Moderate tissue change was observed in mice by application of a 

0.525% solution by spraying or wiping 8 times/day for two consecutive days (31). Slight 

irritation has been observed in rabbits and guinea pigs by application of a 5.25% solution 

(pH 10.7) using a patch (17). Moderate irritation (Primary Irritation Indices of 1.4-1.6) has been 

observed following 4-hour application of hypochlorite bleach (5.25% solution) using two 

different application techniques (chamber and patch)(18, 32). In another test, moderate irritation 

has been observed in rabbits by application of an approximately 5.5% solution (18). Severe 

irritation (scored 5.08/8.00) and corrosive injury were observed following application of 0.5ml of 

undiluted sodium hypochlorite for an unspecified duration to rabbit skin (30). 

4.2.1.2.2.2 Long-term (chronic) exposure

Ingestion

Slight liver damage (biochemical changes) has been observed in rats, when water containing 0.2 

and 0.4% sodium hypochlorite has been given to them for 13 weeks. Approximate doses 

were 200 or 400 mg/kg/day. These effects were not observed in rats which had 

received 25-100 mg/kg/day (cited as 0.025%-0.1%). Some absolute weights, e.g., lungs, liver 

and spleen in males; salivary gland, lungs, heart and brain in females, were significantly lower 

at 400 mg/kg/day (0.4%). But no microscopic changes were observed in any organs (33). Rats 

were given drinking water with 0, 0.05% or 0.01% (males) or 0, 0.1% or 0.2% (females) sodium 

hypochlorite for 2 years. Approximate doses were 0, 50 or 100 mg/kg/day for males or 0, 100 

or 200 mg/kg/day for females. A dose-related in mean body weight has been observed, from the 

sixteenth week on. No other significant changes have been observed (33). In another study, 

effects on the immune system (reduced spleen weight and impaired macrophage functions) 

were observed in rats given drinking water containing 15 or 30 mg/L sodium hypochlorite 

(approximately equivalent to 1.5 or 3 mg/kg/day) for 9 weeks. Where as no harmful effects were 

observed on the immune system at the application of 0.5 mg/kg/day (5 mg/L) of sodium 

hypochlorite (34). No harmful effects were observed in male guinea pigs or male rats, when they 

were exposed to sodium hypochlorite in water (8.1 mg/kg/day sodium hypochlorite; cited 

as 50 mg/L available chlorine for male guinea pigs and up to 16.5 mg/kg/day sodium 

hypochlorite; cited as 50 mg/L available chlorine for male rats) for 5 or 6 weeks, respectively (35). 

Skin sensitization

Negative results (0/20 guinea pigs sensitized) have been obtained for 8% sodium hypochlorite 

solution in a skin sensitization test (18). Insufficient details are available to evaluate a report of a 

positive result (positive reactions in 2/10 animals) obtained using 6% sodium hypochlorite 

(pH 11.2) with the guinea pig ear swelling test for non-immunological contact urticaria (17). 

Carcinogenicity

The International Agency for Research on Cancer (IARC) has concluded that there is inadequate 

evidence for the carcinogenicity of sodium hypochlorite in animals. A significant increase in 

cancer cases was not seen in animals when drinking water containing sodium hypochlorite 

for 2 years at concentrations up to 2,000 mg/L (rats) or 1,000 mg/L (mice) was given (36). 

Similarly, in another study, no-dose related increase in tumour cases were observed in rats, 

which were given drinking water containing 0.05, 0.1 and 0.2% sodium hypochlorite 

(approximately 125 mg/kg/day) for 104 weeks (33). Negative results have been also obtained in 

a 6-generation study in which rats have been given drinking water containing 100 mg/L chlorine 

(approximately 7 mg/kg/day for adults). From a more recent study in which increase in stomach 
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tumour cases (3 different types) have been observed in male rats and increase in lymphomas and 

leukaemia cases have been observed in female rats after receiving 100 mg/L and 750 mg/L 

sodium hypochlorite in drinking water, respectively. But no firm conclusions can be drawn from 

this study, as the study has been limited by factors, e.g., lack of statistical evaluation of the 

results and lack of a dose response relationship (37). Another application of a 1% solution 

(10g/L) to mice for 51 weeks, no significant increase in skin tumour cases has been observed (38). 

Whereas, application of a more than 10.5% solution for 45 times over a period of 245 days 

promoted the development of skin tumours in mice following skin application of a known 

carcinogen. This study is limited by a lack of statistical evaluation (39). 

Teratogenicity, embryotoxicity and/or fetotoxicity

There is insufficient information available to draw any conclusions. No harmful effects on 

growth or survival have been observed in seven generations of rats when they have been given 

chlorinated drinking water containing 100 mg/L available chlorine (approximately equivalent 

to 7 mg/kg/day sodium hypochlorite for adults) (40). 

Reproductive toxicity

There is insufficient information available to draw conclusions. An increase in abnormal sperm 

(shape) has been observed in mice after receiving 1.6 to 4.0 mg/kg/day hypochlorite in drinking 

water. But effect on reproductive outcome has not been assessed in this study (41). In another 

study no effects on fertility have been observed, where a 6-generation study has been performed 

on rats after giving them drinking water containing 100 mg/L chlorine (approximately equivalent 

to 7 mg/kg/day sodium hypochlorite for adults) (40). 

Mutagenicity

Sodium hypochlorite has not been suggested as mutagenic according to the available 

information. A positive result was obtained in a sperm morphology test using live mice. But this 

test can not measure genetic damage directly, as negative results have also been obtained in other 

in vivo tests. Abnormal sperm shape was observed in mice following oral administration of 

1.6-4 mg/kg/day hypochlorite having pH 8.5 for 5 consecutive days. But no other toxic effect 

has been observed (41). Sodium hypochlorite was not mutagenic in other tests (chromosomal 

aberrations, aneuploidy and micronucleus test) also with live mice using similar doses 

(40, 41, 42), whereas positive results have been obtained in a number of tests using bacteria and 

cultured mammalian cells (27, 28-unconfirmed, 34, 35). A negative result (unscheduled DNA 

synthesis) has been obtained in hamster embryo cells (43). 

4.2.1.3 Data on environmental fate and effect under aerobic and anaerobic conditions

4.2.1.3.1 Abiotic degradation of hypochlorite

By direct photolysis, significant degradation always happens. Under the application of sunlight, 

the half-life of 10-15% available hypochlorite solution can be reduced by 3-4 times. It is very 

unstable at pH under 11. The stability is increased by dilution of the product. It is very unstable 

at 25% w/w and loose at 15 degree C in 3 months at 12.5% w/w. With the oxidation reactions 

with different inorganic and organic materials in solutions, chloramines, peroxy radicals and 

oxidized metals have been produced as degradation products. 
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Biotic degradation

Not applicable as hypochlorite is an inorganic compound. 

Potential for bioaccumulation 

Not applicable as hypochlorite is an ionizing inorganic compound. 

4.2.1.4 Physical and chemical properties of hypochlorite

Property Value 

Melting point -6 deg C (5% solution) (44) 

Boiling point Reported to slowly decompose above 40 deg C 

Relative density (specific gravity) About 1.1 (5-10% solution); 

1.2 (15% solution) (water = 1) (44) 

Solubility in water Soluble in all proportions 

Coefficient of oil/water 

distribution (partition coefficient) Log P(oct) = -3.42 (estimated) (45) 

pH value 

9-10 (5% solution; ìneutralî preparation; no 

sodium hydroxide) (21); 

approx. 11 (5% solutions); 

greater than 11 (commercial bleach; 15% sodium 

hypochlorite) (19) 

Vapour density 2.5 (air = 1) 

Vapour pressure Does not form a vapour 

Saturation vapour concentration Not applicable 

Evaporation rate Not available probably very low 

Critical temperature Not applicable 

4.2.2 Data on chlorine

4.2.2.1 Toxic effect of chlorine on aquatic life

A release of large quantity may be harmful to an aquatic environment in specific conditions that 

allow the gas to settle to a body of water. The following aquatic toxicity data are available for 

the chlorine component. 

4.2.2.1.1 Acute toxicity data

Species End point 

Daphnia magna/water flea LC50 = 0.097 mg/L (30 minutes) 

Daphnia magna/water flea LC50 = 0.063 mg/L (60 minutes) 

Gambusia affinis/mosquito fish LC50 = 1.59 mg/L (30 minutes) 

Gambusia affinis/mosquito fish LC50 = 0.84 mg/L (60 minutes) 

Grass shrimp TLm = 22 mg/L (96 hours) 

Ocean spot TLm = 0.14 mg/L (24 hours) 

Daphnia magna/water flea TLm = 0/017 mg/L (46 hours) 

Oncorhyncus kisutsh/ Coho salmon LC50 = 208 g/L (60 minutes) 

Keratella cochlearis TL50 = 0.019 mg/L (4 hours) 
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4.2.2.1.2 Chronic toxicity data

Species End point

Daphnia pulex LC50 = 0.49 mg/L (96 hours) 

Micropterus salmoides, largemouth 

bass LC50 = 0.74 mg/L (24 hours) 

Salmo gardnerii, rainbow trout LC50 = 0.08 mg/L (168 hours) 

Carassium auratus, gold fish TLm = 0.17 mg/L (24 hours) 

Lepomis macrochirus, bluegill

sunfish LC50 = 0.44 mg/L (96 hours) 

Pimphales promelas, fathead minnow LC50 = 0.1 mg/L (96 hours) 

Lepomis cyanellus, green sunfish LC50 = 3.0 mg/L (24 hours) 

4.2.2.2 Toxic effect of chlorine on mammals

Large amount of chlorine gas can have toxic effect on mammals. Following are the different 

aspects of toxicity for the chlorine component. 

4.2.2.2.1 Causes

Chlorine gas is one of the most common irritant. Possible sources of exposure are as follows: 

- industrial bleaching operations; 

- sewage treatment; 

- household accidents involving the inappropriate mixing of hypochlorite cleaning 

solutions with acidic agents; 

- transportation releases; 

- swimming pool chlorination tablet accidents; 

- storage tank failure; and 

- chemical warfare. 

Adverse effects of inappropriate mixtures of household cleaners usually are caused by prolonged 

exposure to an irritant gas in a poorly ventilated area. The most common mixtures of cleaning 

agents are sodium hypochlorite (bleach) with acids or ammonia. Potential irritants released from 

such mixtures are chlorine gas, chloramines, and ammonia gas. 

4.2.2.2.2 Clinical effects

.1 Summary of exposure

Mechanism of activity

The mechanisms of the biological activity of the chlorine are poorly understood 

and the predominant anatomic site of injury may vary, depending on the chemical 

species produced. Cellular injury is believed to result from the oxidation of 

functional groups in cell components, from reactions with tissue water to form 

hypochlorous and hydrochloric acid, and from the generation of free oxygen 

radicals. Although the idea that chlorine causes direct tissue damage by 

generating free oxygen radicals was once accepted, this idea is now controversial. 
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Solubility effects

Hydrochloric acid is highly soluble in water. The predominant targets of the acid 

are the epithelia of the ocular conjunctivae and upper respiratory mucus 

membranes. Hypochlorous acid is also highly water soluble with an injury pattern 

similar to hydrochloric acid. Hypochlorous acid may account for the toxicity of 

elemental chlorine and hydrochloric acid to the human body. 

Early response to chlorine gas 

Chlorine gas, when mixed with ammonia, reacts to form chloramine gas. In the 

presence of water, chloramines decompose to ammonia and hypochlorous acid or 

hydrochloric acid. The early response to chlorine exposure depends on these 

effects: 

.1 concentration of chlorine gas; 

.2 duration of exposure; 

.3 water content of the tissues exposed; and 

.4 individual susceptibility. 

Immediate effects

The immediate effects of chlorine gas toxicity include acute inflammation of the 

conjunctive, nose, pharynx, larynx, trachea, and bronchi. Irritation of the airway 

mucosa leads to local edema secondary to active arterial and capillary hyperemia. 

Plasma exudation results in filling the alveoli with edema fluid, resulting in 

pulmonary congestion. 

Pathologic findings

Pathologic findings are nonspecific. They include severe pulmonary edema, 

pneumonia, hyaline membrane formation, multiple pulmonary thromboses, and 

ulcerative tracheobronchitis. The hallmark of pulmonary injury associated with 

chlorine toxicity is pulmonary edema, manifested as hypoxia. Noncardiogenic 

pulmonary edema is thought to occur when there is a loss of pulmonary capillary 

integrity, and subsequent transfusion of fluid into the alveolus is present. The 

onset can occur within minutes or hours, depending upon severity of exposure. 

Persistent hypoxemia is associated with a higher mortality rate. 

The eye seldom is damaged severely by chlorine gas toxicity; however, burns and 

corneal abrasions have occurred. Acids formed by the chlorine gas reaction with 

the conjunctival mucous membranes are buffered, in part, by the tear film and the 

proteins present in tears. Consequently, acid burns to the eye typically cause 

epithelial and basement membrane damage but rarely damage deep endothelial 

cells. Acid burns to the periphery of the cornea and conjunctiva often heal 

uneventfully, while burns to the centre of the cornea may lead to corneal ulcer 

formation and subsequent scarring. 
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In animal models of chlorine gas toxicity, immediate respiratory arrest occurs 

at 2,000 mg/L, with the lethal concentration for 50% of exposed animals in the 

range of 800-1,000 mg/L. Bronchial constriction occurs in the 200 mg/L range 

with evidence of effects on ciliate activity at exposure levels as low as 18 mg/L. 

With acute exposures of 50 mg/L and subacute inhalation as low as 9 mg/L, 

chemical pneumonitis and bronchiolitis obliterans have been noted. Mild focal 

irritation of the nose and trachea without lower respiratory effects occur at 2 mg/L. 

In one study of chlorine gas toxicity conducted on human volunteers, 4 hours of 

exposure to chlorine at 1 mg/L produced significant decreases in forced vital 

capacity (FVC), forced expiratory volume in one second (FEV1), and peak 

expiratory flow rate. An increase in airway resistance was demonstrated. In a 

controlled volunteer study, patients with hyper reactive airways demonstrated an 

exaggerated airway response to exposure of 1 mg/L chlorine gas. While in another 

study, patients with rhinitis and advanced age demonstrated a significantly greater 

nasal mucosal congestive response to chlorine gas challenge than patients who did 

not have rhinitis or those of younger age. However, the mechanism of response to 

chlorine in nasal tissue does not appear to include mast cell degranulation. 

Frequency

In the United States: Chlorine gas is one of the most common single, irritant, 

inhalation exposures, occupationally and environmentally. In 1983, an 

estimated 191,000 United States workers were at risk of exposure to chlorine in 

various forms. In a recent study of 323 cases of inhalation exposures reported to 

poison control centres, the largest single source of exposure (21%) was caused by 

mixing bleach with other products. The greatest numbers of victims were injured 

in manufacturing and the entertainment and recreation services sectors. 

Internationally: Internationally, chlorine gas accounts for the largest single cause of 

major toxic release incidents. Use of chlorine internationally is parallel to use by 

the United States in chemical, paper, and textile industries and in sewage treatment. 

Mortality/Morbidity: Five-year cumulative data (1988-1992) from the American 

Association of Poison Controls Centersí National Data Collection System 

revealed 27,788 exposures to chlorine. Of these exposures, the outcome was 

categorized in 21,437 cases; 40 resulted in a major effect, 2,091 resulted in a 

moderate effect, 17,024 resulted in a minor effect, and 2,099 had no effect. Three 

fatalities occurred. Another case series associated worse outcomes with advanced 

age, initial low peak expiratory flow rate (PEFR), exposure in an enclosed space, 

and prolonged short- and long-term exposure. 

.1 Minor effects include signs or symptoms that are minimally 

bothersome and quickly resolved. 

.2 Moderate effects include signs or symptoms that are more 

pronounced or more prolonged than minor effects. These may 

have asystemic nature and usually require some form of treatment. 

.3 Major effects include signs or symptoms that are life-threatening or 

result in significant residual disability or disfigurement. 
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Symptoms of exposure to chlorine gas

It includes rhinorrhea, nausea, headache, dizziness and syncope, muscle weakness, 

choking (cramps in the pharyngeal muscles), epigastric pain, a feeling of 

suffocation, apprehension and anxiety, dermatitis, retrosternal burning and 

substernal pain, respiratory distress, shortness of breath, pneumonia, 

bronchospasm and acute lung injury. Bronchopneumonia or respiratory collapse 

may be lethal complications. 

.2 Acute exposure

(i) Inhalation

It is the main route of chlorine gas exposure. Chlorine gas vapours are heavy and 

settle in low areas; odour is not a good indicator of exposure severity. Chlorine 

gas is severely irritating on contact and can be caustic to the eyes, skin, nose, 

throat, and mucous membranes; exposure can result in severe or permanent eye 

injury. Contact with the escaping compressed liquid can cause frostbite and/or 

chemical burns to the eyes and skin. Chlorine combines with tissue water to 

produce HCl, producing injury and reactive oxygen species. Respiratory 

symptoms may be immediate or delayed up to several hours after exposure. 

Symptoms generally resolve within 6 hours after mild exposures, but may 

continue for more than 24 hours after severe exposures. Deterioration may 

continue for several hours. 

(ii) Mixing household cleaning agents (bleach with acids or ammonia)

It produces chlorine gas and other active chlorine compounds such as 

chloramines. For example, mixing household bleach (sodium hypochlorite) with 

acid toilet bowl cleaners produces chlorine gas. Ammonia mixed with bleach 

results in the release of chloramine. A single acute exposure to these reaction 

products commonly produces coughing, lacrimation, conjunctivitis, a burning 

sensation in the chest, pneumonitis, and tachycardia. A few patients may 

experience vomiting, diaphoresis and headache. Severe cases may result in acute 

lung injury. 

(iii) Green hair, dental enamel erosion, conjunctivitis, lacrimation, nasal and 

throat irritation may occur. Anosmia has also been reported. 

(iv) Cardiovascular effect

Tachycardia and initial hypertension followed by hypotension may occur. 

Cardiovascular collapse may ensue following severe exposure. 

(v) Respiratory effect

.1 Feeling of burning and suffocation, coughing, choking, laryngeal 

edema, bronchospasm, and hypoxia may occur. In high 

concentrations, syncope and almost immediate death may occur. 

Acute lung injury is common after severe exposure. 
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.2 Exposures produced flu-like symptoms and high risk of developing 

reactive airway dysfunction syndrome. 

.3 Pulmonary dysfunction has been reported in some individuals 

following severe inhalational effect. 

(vi) Neurological effect

Headache may develop. Agitation and anxiety may develop in patients with 

significant respiratory compromise. 

(vii) Gastrointestinal effect

Vomiting may occur following initial exposure. 

(viii) Acid base effect 

Following severe exposure, metabolic acidosis secondary to hypoxemia may be 

noted. 

(ix) Dermatological effect 

Dermal exposure may cause erythema, pain, irritation, and cutaneous burns. 

(x) Reproductive hazards

Chlorine (as hypochlorite) is teratogenic in experimental animals. Evaluations of 

sperm morphology in murine experiments demonstrated the presence of 

mutations. 

(xi) Carcinogenicity

.1 Human effect

Lymphoma has been observed in relation to water treatment with 

chlorine. Associations with increased renal, bladder and gastric 

cancers have also been found but firm conclusions cannot be drawn 

because of mixed exposures with caustic acids. 

.2 Effect on animals

Chlorine gas was not carcinogenic in mice and rats exposed to 

varying concentrations. Chlorine administered in drinking water 

produced lymphomas and/or leukaemia in rats, but was not 

carcinogenic in a third study. 

(xii) Genotoxicity

Haloacetonitriles have produced DNA strand breaks in cultured human cells. 

Mutations have been detected in S typhimurium and chromosome aberrations 

have been detected in human lymphocytes. 
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Acute effect of chlorine exposure

Exposure to 

Chlorine Gas Acute Effect 

1 to 3 mg/L Mild irritation 

3 to 6 mg/L 

Itching, stinging and burning of the eyes, lacrimation, 

blepharospasm, as well as burning of the nose and throat, 

sneezing, coughing, and bloody nose or sputum 

5 to 10 mg/L Moderate upper respiratory irritation 

10 to 20 mg/L Intense irritation 

30 mg/L chest pain, vomiting, dyspnea and cough 

Acute toxicological effect

Species End Point 

Human (inhalation) LCLo = 2530/m3 (30 minutes); Pulmonary effects 

Human (inhalation) LCLo = 500 mg/m3 (5 minutes) 

Rat (inhalation) LC50 = 293 mg/L (1 hour) 

Mouse (inhalation) LC50 = 137mg/L (1 hour) 

 .3 Chronic exposure

Moderate or severe exposure (associated with acute marked airflow obstruction 

and air-trapping) often results in residual pulmonary dysfunction, most notably 

hyperreactive airways and low residual volumes. These long-term sequelae of 

acute exposure may persist for several years. 

Chronic exposure to chlorine gas may cause dyspnea, palpitations, chest pain, 

reactive upper airways dysfunction syndrome, dental enamel erosion, and an 

increased prevalence of viral syndromes. Chronic exposure to 15 mg/L produced 

coughing, hemoptysis, chest pain and sore throat. Chronic exposure to chlorine 

gas is one of the most frequent causes of occupational asthma. 

Hypoxia is common, whereas CO2 retention and pulmonary function 

abnormalities are generally less common. Rales, hypoxemia and airway 

obstruction have been found. 

Chronic effect of chlorine exposure 

Exposure to Chlorine Gas Chronic Effect 

14 mg/L (30 minutes) Severe pulmonary damages 

430 mg/L or more (30 minutes) May be fatal 

34 to 51 mg/L (60 minutes) May be fatal 

1,000 mg/L Can be fatal within a few breaths 

Chronic toxicological effect 

Species End Point 

Dog (inhalation) LCLo = 800 mg/L (30 minutes) 

Cat (inhalation) LCLo = 660 mg/L (4 hours) 

Rabbit (inhalation) LDLo = 660 mg/L (4 hours) 
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History of toxicity of chlorine 

- cough (52-80%); 

- shortness of breath (20-51%); 

- chest pain (33%); 

- burning sensation in the throat and substernal area (14%); 

- nausea or vomiting (8%); 

- ocular and nasal irritation (4-6%); 

- choking; 

- muscle weakness; 

- dizziness; 

- abdominal discomfort; and 

- headache. 

Physical toxic effect of chlorine

- decreased breath sounds; 

- tachypnea; 

- tachycardia; 

- wheezing; 

- nasal flaring; 

- intercostal and subcostal retractions; 

- cyanosis; 

- rhinorrhea; 

- lacrimation; 

- hoarseness of the voice or stridor; 

- rales (acute respiratory distress syndrome [ARDS]/noncardiogenic 

pulmonary edema); and 

- crepitus (associated with pneumomediastinum). 

4.2.2.3 Physical and chemical properties of chlorine

Physical State Gas 

Colour Yellow or green 

Odour Distinct odour, irritating odour 

Molecular weight 70.906 

Molecular formula Cl2 

Boiling point -31F (-35C) 

Freezing point -150F (-101C) 

Vapour pressure 5168 mm Hg@ 21C 

Vapour density (air = 1) 2.49 

Specific gravity Not applicable 

Density 3.214 g/L @ 0C 

Water solubility 1.46% @ 0C 

pH Not applicable 

Volatility Not applicable 

Odour threshold 0.01 mg/L 

Evaporation rate Not applicable 

Viscosity 0.01327 cP @ 20C 

Coefficient of water/oil distribution Not applicable 

Solvent solubility Soluble: alkali 
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4.2.3 Hydroxyl radical

4.2.3.1 Hydroxyl radical production by electrolytic method

Hydroxyl radicals can be generated from the oxidation of water. Organic compounds were 

completely degraded by the reaction with generated OH radicals. But in the electrochemical 

reactor the radicals could not be monitored directly due to its very short life span in aqueous 

solution. A probe compound, p-chloro benzoate can be used which reacts very fast with 

OH radicals with a second-order rate coefficient k (OH + pCBA) = 5 x 109 M-1s

-1, it does not 

react with other reaction species. So OH radical can be measured from the decrease of p-CBA. 

Here titanium and titanium coated with ruthenium oxide and platinum oxide used as cathode and 

anode, respectively, in the electrochemical reactor. There are some factors which affect the 

production rate of OH radicals in the reactor. 

.1 Inter electrode gap: With an increase in the inter electrode gap the rate of 

production of OH radicals will be decreased, due to increase in the electrical 

resistance. In the considered experiment, an applied current was decreased from 

1A to 0.6A when the electrode gap increased from 10 mm to 20 mm. 

.2 Temperature: With an increase in the temperature the production rate of 

OH radical will be increased due to increase in mass transport of the electroactive 

species to the electrode surface. 

.3 Applied voltage: In the considered experiment, the applied voltage has been 

ranged between 2V to 6V. OH radical production was significantly enhanced 

when applied voltage was increased from 2V to 4V. As the limiting current for 

OH radical production in the given condition flows at between 2V and 4V, further 

increase of applied voltage did not enhance the OH radical production. 

.4 Electrical conductivity: The OH radical production has been increased with the 

increase in the electrical conductivity. In the considered experiment, during the 

variation of conductivity between 8ms cm-1 to 10ms cm-1, there was not much 

difference in the production. But when it is 20ms cm-1, then the production rate 

has been enhanced significantly. 

4.2.3.2 Toxic effect of hydroxyl ions on fishes

The presence of hydroxyl ions in water is the key factor for controlling the pH of the aquatic 

environment. Whenever higher amount of hydroxyl ions is present, the pH of the water will be 

in higher range. Therefore, the presence of hydroxyl radicals affects the aquatic life indirectly by 

changing the pH of the water. 

Each species of fish has its own very narrow range of pH preference and levels outside of this 

range will cause health problems. For example, koi prefer a range between 7 and 8.5, while 

some tropical fish prefer water that is slightly acidic. There are several ways that pH can affect 

fish health. 

.1 High acidity or alkalinity can cause direct physical damage to skin, gills and eyes. 
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.2 Prolonged exposure to sub-lethal pH levels can cause stress, increase mucus 

production and encourage epithelial hyperplasia (thickening of the skin or gill 

epithelia) with sometimes fatal consequences. 

.3 Fish also have to maintain their own constant internal pH. Even small 

fluctuations of blood pH can prove fatal. Extreme external or water pH can 

influence and affect blood pH, resulting in either acidosis or alkalosis of the blood. 

.4 The other consideration is diurnal shifts in pH, mainly as a consequence of 

photosynthesis as explained above. Large, fluctuations even though they may still 

be within the preferred range are likely to be stressful and damaging to health. 

.5 Changes in pH will affect the toxicity of many dissolved compounds. 

For example, ammonia becomes more toxic as pH increases. 

4.2.3.3 Toxic effect of hydroxyl radicals in mammals

The systemic toxicity of hydroxyl ions confounds with an elevated blood pH. The normal pH of 

blood is 7.35. Alkalosis causes hyperactivity to the central nervous system with above pH 7.8, 

tetanus, extreme excitability, convulsions and respiratory stop. The blood pH is regulated by 

three distinct mechanisms. An immediate mechanism is the buffering capacity of bicarbonate 

(1.5 g/L). A short-term mechanism is the respiration compensation. Alkalosis will be decreased 

by a slow and superficial respiration, a low CO2 expiration and an accumulation of HClO3

-

(higher than 1.7 g/L). A long-term mechanism is the renal compensation. 

4.2.4 Data on the effluent of electrolytic disinfection system

The data on the toxicity of electric disinfection of water has its limits because the evaluation 

technology required has yet to be implemented. Because the micro-organisms are affected by not 

just the residual Active Substances, but also differences in potential, radicals and electrical 

oxidization during electric disinfection, it is difficult to measure the role these residual Active 

Substances have in the toxicity of the water. The Active Substances in disinfected water are 

types of residual chlorides so that the data given in the above paragraph can also be applied to 

electrochemically disinfected water. 

5 RISK CHARACTERIZATION

5.1 Screening for persistency, bioaccumulation and toxicity

.1 Persistence (P) 

By direct photolysis, significant degradation always happens. In the oxidation 

reactions with different inorganic and organic materials in solutions, peroxy 

radicals and oxidized metals have been produced as degradation products. Due to 

its degradation, total residual chlorine is not persistent in the environment. In 

nature, half-life is in the order of hours or a few days at maximum. 

.2 Bioaccumulation (B) 

Due to the high water solubility and the low octanol water partition coefficients of 

the hypochlorite, there is no concern for a possible bio-accumulation potential 
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(log Kow below 0). A rat study using radiolabelled hypochlorous acid has shown 

that it is absorbed fairly rapidly in serum and eliminated from plasma with a halflife of 44 hours. Hypochlorite is an ionizing inorganic compound so that it does 

not accumulate in the body. 

.3 Toxicity (T) 

There are no indications for relevant effects concerning carcinogenicity, 

mutagenicity or reproductive toxicity. The active component, hypochlorite does 

not fulfil the PBT criteria as outlined in document MEPC 53/2/1, annex, 

paragraph 6.4.1. 

Table 3: Criteria for identification of PBT substances 

Criterion PBT criteria 

Persistence 

half-life: 

> 60 days in marine water, or 

> 40 days in freshwater, or 

> 180 days in marine sediment, or 

120 days in freshwater sediment 

Bioaccumulation CF > 2,000 or 

LogPoctanol/water ≥3 

Toxicity Chronic NOEC < 0.01 mg/l 

5.2 Testing toxicity of the treated ballast water

The toxicity of the treated ballast water can be evaluated by the concentration of residual Active 

Substances in it. Because the concentration of Active Substances created during electrolytic 

disinfection, excluding total residual chlorine, is very low, we can test the toxicity of treated 

ballast water by the concentration of total residual chlorine in it. In the United States, they 

produce and supply the drinking water using the electrolytic disinfection process. Because total 

residual chlorine is mainly used in the disinfection of drinking water, their toxicity in low 

concentrations has already been assessed thoroughly. 

When the system is operating for disinfection, the concentration of total residual chlorine that is 

produced is about 30mg/L. It is degraded in the ballast tank and thus the final concentration of 

total residual chlorine that is discharged is less than a few mg/L. In acute toxicity tests, 

hypochlorite solution of 10,000 mg/L was placed on the skin for 48 hours. There was no 

irritation or discoloration of the skin. Total residual chlorine used for ballast water treatment is 

too low to show any toxicity it may differ according to the amount of microorganisms in the 

water. The half-life of residual chlorine was half a day in light conditions. After a day it was 

almost completely decomposed to the level below detection limit. Without light, the half-life 

was about three days. The lower the amount of organisms is, the longer it took for the residual 

chlorine to completely decompose. The degradation rate of residual chlorine is dependent on the 

amount of reducing agents in seawater. 

Taking into consideration that the NOEC of sodium hypochlorite is 0.087mg/L, and that the total 

residual chlorine at the concentration of 10-30 mg/L recommended for Ballast water treatment is 

completely degraded already after 1.1 days under light condition, it can be assumed that there are 

no biological effects of treated ballast water. 
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5.3 Risk characterization and analysis

In order to calculate the half-life of Active Substances in treated water, total residual chlorine in 

electrochemically disinfected water was monitored, and the results are shown below. The 

experiment was conducted with seawater containing 6,837 cells/ml of phytoplankton, 337 inds./l

of zooplankton at 5.2 volts (14.5 ampere). 

Under in situ light condition, total residual chlorine (TRC) decreased to below detection limit 

after about one day. The half-life under the dark condition reached before the two days. 

5.4 Effect of TRC discharged to seawater on aquatic organisms

TRC discharged to seawater is readily degraded to below detection limit under sunlight. In 

addition to that, as shown in table 6, when dilution effect (about 5,000 times dilution) is 

considered, TRC goes down to a level in nature. Therefore, there is no effect on aquatic 

organisms. 

Table 4: Treated ballast water discharge Scenario for hypochlorite 

Initial dose 30 mg/l 

Retention (degradation) time [h] zero 

Predicted environmental 

concentration 

zero 

No observed effect concentration 0.014 mg/l 

PEC/NOEC ratio 0.087 mg/l 

Port statistics 0.17 

Selected port Rotterdam 

Water volume 840,000,000 t 

Number of incoming ships 29,450/a; 80/d 

Total gross tonnage 489,222,000 GT/a; 1,323,074 GT/d 

Average amount of ballast water 144,876,600 t/a; 396,922t/d 

5.5 Bioaccumulation, octanol/water partition coefficients

Log P(oct) of hypochlorite is reported to be -3.42. Low octanol water partition coefficient 

indicates low potential for bioaccumulation. Hydrochloric acid is highly soluble in water and an 

ionizing inorganic compound so that this can not be accumulated in biota. 

5.6 Sediment toxicity

From the physical and chemical properties, the high water solubility, the low log kow and the 

instability in water, it is not expected that the hypochlorite will reach the sediment to a 

considerable extent and accumulate in sediment. 

6 EVALUATION CRITERIA

6.1 Ship and personnel safety 

Total residual chlorine produced typically ranges from 10 to 30 mg/L in the Electro-Clean system 

operating with an applied voltage lower than 7 volts. No skin irritation was experienced by 

20 volunteers after application of a 1% hypochlorite solution (pH unspecified) for 48 hours under 
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a patch. The possibility of risk from the electrochemically treated water to personnel does not 

exist. The system is also sealed tightly. This makes human exposure to treated water impossible 

under normal operational conditions. Since the Electro-Clean system is fully automated, 

cutting-off electricity to the system alone can ensure the safety of the ship and personnel at the 

time of emergency. 

6.2 Environment protection

The concentration levels of total residual chlorine in treated water discharged from the 

Electro-Clean system is extremely low. TRC is easily decomposed by sunlight, micro-organisms 

and other reductants. Thus, residual chlorine will not be accumulated in harbors or ports. 

Octanol/water partition coefficient of TRC is calculated to be log P(oct) = -3.42. TRC is not 

persistent and bio-accumulative. In reality, chlorine is used for the disinfection of drinking water 

not only in the United Kingdom and the United States, but also in most other countries. 

7 REGULATION OF THE USE OF ACTIVE SUBSTANCES AND PREPARATIONS 

7.1 Handling of Active Substances and preparations

Electro-Clean for ballast water treatment system uses the strainer already installed on the ship to 

remove the large pieces of suspended solids. The Electro-Clean system mainly uses radicals, 

electric voltage, etc. to disinfect. These Active Substances disappear in seconds after they are 

produced. 

The concentration levels of total residual chlorine (TRC) formed during operation varies 

according to water temperature, conductivity, organic and inorganic substances in the water. 

TRC is typically in the ranges of 10 and 30 mg/L. The operator or ship crew does not have to 

take special precautions when dealing with the ballast water. The system automatically controls 

the amount of voltage and current in order to maintain the concentration level of active chlorides 

to less than 30 mg/L. 

7.2 Hazard documentation and labelling

The reactivity of the total residual chlorine in electrolytically disinfected ballast water is 

extremely high so that it is rapidly decomposed in seawater. The concentration level of total 

residual chloride in the ballast water is below 30mg/L. There is no possibility of explosion. 

Although there are only few precautions to be taken for management, there may be need to 

ventilate hydrogen generated during the electrolytic disinfection in order to prevent 

accumulation. 

A document that deals with the harmful substances produced during electrolysis including the 

MSDS (IMDG code entry) data has been summarized and provided below. 

MSDS

The Material Safety Data of 2~3% w/w sodium hypochlorite solution have been reported to be 

hazardous in case of eye and skin contact. For the carcinogenic effects, this material is not 

known to cause cancer in animals or humans. There is no available Material Safety Data sheet 

for the 0.003% w/w sodium hypochlorite solution which is generated in the Electro-Clean 

system. 
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IMDG 

IMDG Code 8186, UN No.1791, Class 8, Packaging Group II/III, EmS No.8-08, MFAG table 

No.741 covers the hypochlorite solutions with more than 5% available chlorine. However, it does 

not cover the 0.003% sodium hypochlorite solution which is generated in the Electro-Clean system. 

Conclusion

.1 It was found that total residual chlorine at the concentration of 10~30mg/L 

recommended for ballast water treatment is completely degraded already 

after 1.1 days under light condition. 

.2 The hydrogen peroxide and ozone concentration of the electrolytic solution is very 

low in comparison with the free chlorine. The maximum concentration produced 

during electrolysis of seawater is below 0.1 mg/L for both hydrogen peroxide and 

ozone. 

.3 From the acute toxicity test, no skin irritation was experienced by 20 volunteers 

after application of a 1% hypochlorite solution (pH unspecified) for 48 hours 

under a patch. The possibility of danger to personnel from the electrolytically 

treated water does not exist. 

.4 Since chlorine is being used to disinfect drinking water not only in the United 

Kingdom and the United States, but also in most other countries, there is almost 

no concern over PBT levels. 

.5 The half-life of total residual chlorine was 0.58 day under light condition 

and 2.0 days under dark condition. No danger to humans and environment is 

expected. 

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