Chlorine

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Persistence Assessment

 

In natural water, the Cl₂molecule as well as hypochlorite ions are not stable due to the presence of organic and inorganic matter. The half-life of hypochlorite is estimated to be less than 2 hours due to reduction and photolysis. The free available chlorine reacts to form various chlorinated by-products, e. g. chloramines and chloromethanes. In sewage chlorine is mainly present in the form of chloramines, as hypochlorous acid undergoes a fast decay (SIAR, 2003).

In the atmosphere, chlorine mainly undergoes photolysis: Cl₂+ hν => 2 Cl°.

The half-lifetime for that process has been estimated to be in the order of 1–4 hours, depending on the time of the day (Hov, 1985; Peterson, 1976). Calculations show that half-lives for chlorine photolysis can range from less than 5 minutes to several hours, depending on the time of day, with representative values for latitudes 40°N and 55°N. The resulting chlorine atoms can then react with species present in the atmosphere such as ozone and saturated and unsaturated hydrocarbons. Recombination of chlorine after dissociation can be neglected due to the fast reaction with other species and due to the low concentration of chlorine.

Thus, chlorine was not considered persistent.

 

Bioaccumulation Assessment

 

Chlorine does not bioaccumulate or bioconcentrate, because of its water solubility and high reactivity.The concentration of hypochlorite in the environment is modelled by Vandepitte and Schowanek and is estimated to drop down to “zero” within the first minutes after release in the sewer. In addition, according to the hypothesised logKow = - 0.87 no bioaccumulation is expected.

 

Toxicity Assessment

 

Toxicity Assessment

Criterion	Substance assessment
Short-term aquatic toxicity (algae, daphnia, fish)	EC50 or LC50 < 0.01 mg/LT, criterion considered to be fulfilled   - Short-term Toxicity to Fish: LC50(96h) for marine water fish = 0.032 mg/L   - Short-term toxicity to aquatic invertebrates: EC50(48h) marine water invertebrates = 0.026 mg/L (OECD 202)   - Toxicity to aquatic algae: EC10/LC10 or NOEC(7d) freshwater algae = 0.002 mg/L
Avian toxicity (subchronic or chronic toxicity or toxic for reproduction)	NOEC < 30 mg/kg food =T   - NOEC long-term Toxicity to rat: NOAELMammal food_chronic*20^#= NOECMammal, food_chronic= 1000 mg/kg food
The substance is classified as carcinogenic (category 1 or 2), mutagenic (category 1 or 2), or toxic for reproduction (category 1, 2, or 3), or there is other evidence of chronic toxicity, as identified by the classifications: T, R48, or Xn, R48 according to Directive 67/548/EEC.	Sodium hypochlorite is not classified as carcinogenic, mutagenic or toxic for reproduction and not classified with R48

#Conversion factor from NOAEL to NOEC for Rattus norvegicus

 

Based on the results of the toxicity assessment to aquatic algae sodium hypochlorite fulfilled the toxic criterion.