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EC number: 203-742-5
CAS number: 110-16-7
Maleic acid was tested as corrosive in an in vitro corrosion study
conducted according to OECD 435. Additional data is supporting the
irritation potential of the target substance (Sax, 1989; Smith, 1993 and
Britz, 1979). Data from an in vivo skin irritation study showed, that
the structural analogue Maleic anhydride can also be considered as
corrosive to the skin.
Based on available data from maleic acid and from the structural
analogue Maleic anhydride, the target substance is considered to
be severely irritating to the eyes and to have the potential of causing
serious damage to the eyes.
This report describes the ability of Maleic acid to pass through a
bio-barrier and to elicit a colour change in the underlying liquid
chemical detection system. The study procedures described in this report
were based on the most recent OECD guideline OECD 435. Maleic acid was a
white solid with a purity of 100.1%. The test substance compatibility
test showed that Maleic acid was compatible with the chemical detection
system. Based on the acid reserve, Maleic acid was classified as a
timescale 1 compound. Maleic acid was applied directly (approximately
500 mg) on top of the bio-barrier matrix. The elapsed time between
application and penetration was determined by monitoring changes in the
chemical detection system. The penetration time of Maleic acid was 25
minutes. Since Maleic acid was a timescale 1 test substance and showed a
mean penetration time of 25 minutes, based on this test Maleic acid
would be classified as Skin Corrosive 1B (CLP) and UN packing group II
(= GHS 1B). The negative control citric acid (10%) showed a mean
penetration time of >60 minutes (actual penetration time 95 minutes) and
was therefore non-corrosive. The positive control sodium hydroxide (as
it is) showed a mean penetration time of 22 minutes and was therefore
classified as UN packing group II (=GSH 1B). It was therefore concluded
that the test system functioned properly. Finally, it is concluded that
this test is valid and that Maleic acid would be classified as Skin
Corrosive 1B (CLP) and UN packing group II (= GHS 1B) in the Corrositex®
assay under the experimental conditions described in this report.
Test substance was administered undiluted at a dose of 0.1 g to
the eyes of rabbits (three/sex). The treated eye of each rabbit was
examined 1, 24, and 48 hours following test article
administration. According to the study protocol, treated eyes were to be
examined a minimum of 72 hours after dosing. However, due to signs of
severe ocular irritation, the study was terminated following the 48-hour
No deaths occurred during the study. The maximum eye irritation
score was 106.7 (out of a maximum of 110). The study was terminated at
the 48-hour postdosing timepoint. The test substance was considered as
highly irritating to the eyes of rabbits and classification as H318 is
warranted in accordance to CLP regulation 1272/2008.
Supporting studies conducted with Maleic acid showed the
irritating potential to the skin of rabbits and of humans.
Moreover, based on the results from an in vitro skin corrosion
study conducted in accordance with OECD 435, the target substance can be
considered to be corrosive.
In addition, available data from the structural analogue Maleic
anhydride showed that the test item was severely irritating to the skin
of rabbits after application of 0.5 g to the skin for 4 hours. The mean
irritation scores for erythema and oedema ranged from 3.67 to 4.00
throughout the 7-day observation period (Chevron Chemical Company,
1976). Maleic anhydride hydrolyses under test conditions. As a result it
is believed that maleic acid and its sodium salt were the test materials
investigated in this study.
Maleic anhydride is severely irritating to the eyes of rabbits. In
one study with maleic anhydride the mean conjunctival erythema scores at
24 and 48 hours were 2.0 and 3.0, respectively. The mean conjunctival
chemosis scores at 24 and 48 hours were 4.0 and 4.0, respectively. The
corneal opacity scores at 24 and 48 hours were 3.8 and 3.8,
respectively. The iridial lesions scores at 24 and 48 hours were 2.0 and
2.0, respectively. The study was terminated at the 48-hour postdosing
timepoint. Maleic anhydride hydrolyses under test conditions. As a
result it is believed that maleic acid and its sodium salt were the test
materials investigated in this study.
In a supporting study with maleic acid doses of 100 mg or
application of 1% concentration of maleic acid for 2 minutes resulted in
moderate to severe eye irritation, in another study application of a 10
% solution for 30 seconds resulted in permanent opacity of the cornea of
Based on the results from an in vitro skin corrosion study (OECD 435)
and from an in vivo skin irritation study conducted with the structural
analogue Maleic anhydride, the target substance does warrant
classification for skin corrosion (Skin Corr 1B, H314). Moreover, based
on the results from the structural analogue Maleic anhydride, the target
substance can be considered to be severely irritating to the eye (H318).
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