Chlorine

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:

0.03 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:

hazard related to composition of atmosphere 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 compartment/endpoint. PNEC's were derived from sodium hypochlorite data (read-across, justification see section 6.1).

Naming rules and conversion factors for different types of concentration given for chlorine:

“Available chlorine” corresponds to ion ClO- and to gases HOCl and Cl₂dissolved 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 gases HOCl and Cl₂dissolved 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 Cl₂for 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

Read-across from sodium hypochlorite (justification see IUCLID5 section 6.1 or CSR section 7.1.1):

Acute toxicity:

Invertebrates and fish are equally sensitive to the toxic effects of sodium hypochlorite/chlorine and allows one to conclude, based on the weight of evidence, 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. This means that an “M-factor” of 10 should be assigned to sodium hypochlorite. The new state of the art daphnia study supports this and demonstrates that the findings noted in literature (sources of limited validity (<0.01 mg/L)) are not relevant for Classification and Labelling deduction.

However, this does not cover the current legislation CLP (GHS) according to annex 6 of regulation 1272/2008 for chlorine (1. ATP).

DSD

-classified with R50 "very toxic to aquatic organisms" and labelled N

- specific concentration limit: N; R50: C ≥ 0.25 %

GHS

- classified "acute env. tox. cat. 1" ("H400 Very toxic to aquatic life")

- M-Factor 100

To be in line with the legally binding classification an M-Factor of 100 will be used.

Chronic toxicity:

Sodium hypochlorite/chlorine has not to be classified regarding chronic toxicity as sodium hypochlorite can be regarded as not persistent in the environment (hydrolysis, calculated log Pow = -0.87).

Overview of Results used for Classification and Labelling:

Fish, short-term, freshwater: LC50 = 0.06 mg/L (Heath, 1978)

Fish, short-term, saltwater: LC50 = 0.032 mg/L (Thatcher, 1978)

Fish, long-term, freshwater: NOEC(28 d) = 0.04 mg/L (Goodman, 1983)

Daphnia magna, short-term, freshwater: LC50 = 0.141 mg/L (Gallagher, 2009)

Crassostrea virginica (invertebrate), short-term, saltwater: LC50 = 0.026 mg/L (Roberts, 1978)

Daphnia, long-term, saltwater: NOEC(7 d) = 0.007 mg/L (Linden, 1978)

Algae, long-term, freshwater: IC50(7 d) = 0.023 mg/L (Cairns, 1990)