Sodium hypochlorite

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.21 µg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.26 µg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.042 µg/L

Assessment factor:

50

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

4.69 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

no exposure of sediment expected

Sediment (marine water)

Hazard assessment conclusion:

no exposure of sediment expected

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no exposure of soil expected

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

11.1 mg/kg food

Assessment factor:

90

Additional information

The PNEC´s were derived from the most sensitive test available for each relevant compartment/endpoint.

For information: naming rules and conversion factors for different types of concentration given for sodium hypochlorite/chlorine:

“Available chlorine” corresponds to ion ClO- and to gases HOCl and Cl₂ dissolved in water. It is the oxidizing potential corresponding to the double of chlorine quantity as NaOCl in a concentrated alkaline solution.

“Active chlorine” corresponds to to gases HOCl and Cl₂ dissolved in water for neutral or acidic diluted solutions.

“Total chlorine” corresponds to all species of chlorine in solution: hypochlorite, sodium chloride, chlorites ClO₂^- and chlorates ClO₃^-.

Active chlorine (a.c.) can be given in percentage (w/w) or in g/L (w/v). Conversion from one to another requires density of the solution:

Y% a.c.= X g/L a.c./(d x 10)

Concentration of sodium hypochlorite can be calculated from % a.c. as follows:

MW a.c. (as Cl2) = 71

MW NaOCl = 74.5

% NaOCl = % a.c. x (74.5/71) = % a.c. x 1.05

Formerly, in certain countries, use was made of chlorometric degrees (°chl.). It corresponds to the minimal gaseous chlorine used for preparation of bleach, in litres of Cl₂ for 1 litre of bleach.

Example: 71 g a.c. corresponds to 22.4 L, so 1L concentrated bleach at 9.6 %a.c. contains 110.56 g a.c.. To produce it, 110.56 x (22.4/71) = 34.88 L of chlorine were necessary, hence: 34.88 °chl.

A number of terms can be used to describe chlorine in water, such as ‘free’, ‘active’, ‘available’, ‘combined’ and ‘residual’ chlorine. The following definitions are commonly used:

- Free available chlorine (FAC) is the concentration of chlorine available in a mixture, at equilibrium, of hypochlorous acid and the hypochlorite ion. It is the form in which it is available to act as an oxidant.

- Combined available chlorine (CAC) is the available chlorine as chloramines or other N-Cl linked compounds.

- Total residual/available chlorine (TR/AC) (the terms total residual and total available chlorine can be used interchangeably) relates to the sum of the FAC and CAC.

- Total residual oxidant (TRO) is the sum of all oxidants including non-chlorine species. In water containing bromine, such as seawater, there is displacement of chlorine by bromine resulting in hypobromous acid, hypobromite ions and bromamines. Some authors also mention CPO (chlorine produced oxidants).

Conclusion on classification

Classification of sodium hypochlorite solutions and mixtures according to CLP

1.       Acute environmental toxicity

High quality studies concerning the acute toxicity of sodium hypochlorite to algae and aquatic invertebrates have recently been carried out in order to upgrade the data set available, in the frame of the substance dossiers submitted under REACH and the Biocidal Products Regulation (BPR). Relevant studies are summarised in Table 1.

Table 1. Summary of acute toxicity data for sodium hypochlorite

Year	Author	Test details	Test organism	Result
2013	Liedtke	freshwater	Pseudokirchneriella subcapitata (Algae)	ErC50= 0.0499 mg (nominal)/L ErC50= 0.0365 mg (initial measured)/L
1984	Watkins	freshwater	Myriophyllum spicatum (freshwater vascular plant)	ErC50= 0.1 mg/L
2009	Gallagher	short-term, freshwater	Daphnia magna	EC50-48h = 0.141 mg/L
2011	Gallagher	short term, freshwater	Ceriodaphnia dubia	EC50-48h = 0.035 mg/l
1978	Roberts	short-term, saltwater invertebrate	Crassostrea virginica (oyster)	LC50= 0.026 mg/L
1978	Heath	short-term, freshwater	Fish	LC50= 0.06 mg/L
1978	Thatcher	short-term, saltwater	Fish	LC50= 0.032 mg/L

 

The above data shows that algae, invertebrates and fish are equally sensitive to the toxic effects of sodium hypochlorite and this allows us to conclude that the acute toxicity of sodium hypochlorite to marine and freshwater species lies in the range:0.01 < L(E)C₅₀≤ 0.1 mg/L.With respect to classification rules defined in Annex I, Table 4.1.3 of Regulation (EC) No. 1272/2008 (CLP), concerning multiplying factors for highly toxic components of mixtures,this means that an “M-factor” of 10 should be assigned to sodium hypochlorite with regards to acute toxicity classification.

Sodium hypochlorite is produced as an aqueous solution. According to Table 4.1.1 of the Regulation (EC) No. 1272/2008, pure solutions (i.e. dilutions in water) or mixtures have to be classified depending on the concentration of active chlorine. A proposed classification based on concentration limits is shown below in Table 3. as shown in Table 3. For mixtures, the acute M-Factor = 10 has to be used unless test data for the complete mixture or similar mixtures are available at the formulator level, as described in Figure 4.1.2 of the regulation. Where test data is available, classification of a mixture derived using test data for the complete mixture or similar mixtures will take precedence over classification derived from calculation.

2.       Chronic environmental toxicity

The 2nd Adaptation to Progress of the CLP regulation (EC 286/2011) of 10 March 2011 further modified the classification criteria for aquatic chronic toxicity. This means that for substances, as well as for mixtures, aquatic chronic toxicity data are taken into account for long-term hazard classification. The key studies for chronic aquatic toxicity of sodium hypochlorite are presented in Table 2.

Table 2. Summary of chronic toxicity data for sodium hypochlorite

Year	Author	Test details	Test organism	Result
2013	Liedtke	freshwater	Algae (Pseudokirchneriella subcapitata)	ErC10= 0.0299 mg (nominal)/L, NOECr = 0.0171 mg (nominal)/L ErC10= 0.0199 mg (initial measured)/L, NOECr = 0.0054 mg (initial measured)/L
1990	Cairns	long-term, freshwater	Algae (periphyton)	NOEC (7 d) = 0.0021 mg/L
1978	Liden	long-term, marine water	Oyster	NOEC (7 d) = 0.007 mg/L
1983	Goodman	long-term, marine water	Fish	NOEC (28 d) = 0.04 mg/

 

The above results show NOEC values between 0.002 and 0.04 mg/l, as active chlorine. According to Table 4.1.0 (b)(ii) of the CLP Regulation, as a rapidly degradable substance, a classification as Chronic Category 1 (H410, very toxic to aquatic life with long lasting effects) applies to sodium hypochlorite solutions. Furthermore, using Table 4.1.3, concerning multiplying factors for highly toxic components of mixtures, an “M-factor” of 1 has to be assigned to sodium hypochlorite with regards to chronic toxicity (0,001 < NOEC£0,01; RD component).

 

3.       Proposed classification for environmental toxicity of sodium hypochlorite according to CLP

 

For dilutions and mixtures containing sodium hypochlorite, provided there is no other component classified as hazardous to the aquatic environment, the proposed classification for acute and chronic toxicity of sodium hypochlorite is outlined in Tables 3 & 4. This proposal is based on the key studies and discussion above and taking into consideration the classification criteria set down in Regulation (EC) No. 1272/2008.

 

 

 

 

Table 3. Proposed acute environmental classification

Concentration of sodium hypochlorite solutions (as % active chlorine)	Acute Classification	H Statements	M Factor
≥ 2.5 %	Acute Category 1	H400 (very toxic to aquatic life)	10
< 2.5 %	None	None	N/A

 

Table 4. Proposed chronic environmental classification

Concentration of sodium hypochlorite solutions (as % active chlorine)	Chronic Classification	H Statements	M Factor
≥ 25 %.	Chronic Category 1	H410 (very toxic to aquatic life with long lasting effects)	1
< 25 % but ≥ 2.5 %	Chronic Category 2	H411 (toxic to aquatic life with long lasting effects)	N/A
< 2.5 % but ≥ 0.25 %.	Chronic Category 3	H412 (harmful to aquatic life with long lasting effects)	N/A