2-Propenoic acid, homopolymer

Endpoint summary

Description of key information

Following repeated oral administration of the analogue acrylic acid in drinking water to Wistar rats at the dose levels of 0, 120, 800, 2000 or 5000 ppm (equivalent to 0, 6, 40, 100 or 200 mg/kg and 0, 10, 66, 150 or 375 mg/kg, for males and females respectively) for 12 months, the dose of 800 ppm in males (equivalent to 40 mg/kg) was identified as a NOAEL based on decreased water intake and body weight at higher dose levels. No target organs were identified.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

chronic toxicity: oral

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
- Read-across hypothesis: "Different compounds have the same type of effect(s)"

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
- Target chemical: 2-Propenoic acid, homopolymer (purity ≥ 99.0%) = UVCB substance composed of acrylic acid monomers (Mw = 72 g/mol) and 2-carboxyethyl acrylate oligomers (average Mw = 208.8 g/mol)
- Source chemical: Acrylic acid = monoconstituent substance composed of acrylic acid monomers (Mw = 72 g/mol)

3. ANALOGUE APPROACH JUSTIFICATION
- Common structure: the constituents of the target and source chemicals share identical functional groups (i.e. one terminal carboxylic acid group and one terminal vinyl group) and only differ in the presence/absence of one or several -CH2-CH2-COO- pattern(s) in their structural backbones. This pattern being introduced as a result of (poly)addition reactions, it is only present in the polymerized units of acrylic acid (average number of -CH2-CH2-COO- patterns per vinyl group: < 3) and is absent from the monomer units.
- Common physico-chemical/fate properties: the target and source chemicals are both hydrophylic substances (log Pow < 1) with a high solubility in water and a low volatility (VP < 5 hPa). Both substances have a low potential for bioaccumulation in living organisms (log Pow < 4) and a low potential for persistence in environmental compartments (rapidly degradable).
- Common mode of action: the toxic effects of the target and source chemicals are expected to result from their acidic character (carboxylic acid group) and from the reactivity of their double bond (vinyl group). As the polyaddition reactions lead only to an increase in the chain length/molecular weight without an increase in the number of reactive functional groups, the low molecular-weight polymerized units of acrylic acid (from the test item) are not expected to exert higher toxicity than the monomer units. As a result, the target chemical, although only partially composed of acrylic acid monomers, is considered at the very worst to be as toxic as the source substance.

Further information (including data matrix) is available in the attached read-across justification document.

Reason / purpose for cross-reference:

read-across source

Key result

Dose descriptor:

NOAEL

Effect level:

40 mg/kg bw/day (nominal)

Based on:

other: conversion of 800 ppm in drinking water

Sex:

male

Basis for effect level:

body weight and weight gain

water consumption and compound intake

Critical effects observed:

no

Conclusions:

Following repeated oral administration of the analogue acrylic acid in drinking water to Wistar rats at the dose levels of 0, 120, 800, 2000 or 5000 ppm (equivalent to 0, 6, 40, 100 or 200 mg/kg and 0, 10, 66, 150 or 375 mg/kg, for males and females respectively) for 12 months, the dose of 800 ppm in males (equivalent to 40 mg/kg) was identified as a NOAEL based on decreased water intake and body weight at higher dose levels. No target organs were identified.

The NOAEL of 40 mg/kg bw/day is read across to the registered substance.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

40 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

Key study of Klimisch reliability 1

System:

other: overall effects on water intake and body weight

Organ:

not specified

Justification for classification or non-classification

Based on the dose levels associated with NOAELs and the absence of target organs in the studies using the analogue acrylic acid, no classification of the registered substance for repeated dose toxicity is warranted.