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Description of key information

For Maltol the following results were derived:


Guideline / Method



Daphnia magna


48-h EC50: 27 mg/L

Key study, Rel. 2. Value derived from read-across to Ethyl Maltol (CAS# 4940-11-8).

Green algae (P. subcapitata)


72 -h ErC50: 7.2 mg/L

72 -h ErC10: 1.8 mg/L

72 -h NOErC: 0.77 mg/L 

Key study, Rel. 2. Value derived from read-across to Ethyl Maltol (CAS# 4940-11-8).

Zebrafish(Brachydanio rerio)

OECD 203/ EC 440/2008 C1/ EPA OCSPP 850.1075/ JMAFF2 -7 -1 -1

96h-LC50 >100 mg/L

96h-NOEC 100mg/L

96H-LOEC >100mg/L

Key study, Rel. 1. experimental study

Additional information

For Maltol no aquatic toxicity information is available for short-term toxicity to aqutic invertebrates and toxicity to aquatic algae and cyanobacteria, and therefore information from Ethyl maltol is used to fill this data gap.

The read across justification is presented below. The executive summaries of these ecotoxicity studies can be found in the respective endpoint summary of the species being tested.

Aquatic toxicity of Maltol (CAS #118-71-8) based on read across from data available for Ethyl Maltol (CAS #4940-11-8)


Introduction and hypothesis for the analogue approach

Maltol is a 3-hydroxy-4-pyrone which is methylated at its 2-position. No experimental aquatic toxicity data are available for Maltol. For the assessment of the aquatic toxicity of Maltol, read-across is performed to the close structural analogue Ethyl Maltol. In accordance with Article 13 of REACH, lacking information can be generated by other means, i.e. applying alternative methods such as in vitro tests, QSARs, grouping and read-across. For assessing the aquatic toxicity of Maltol the analogue approach is selected because for a closely related analogue, Ethyl Maltol, reliableaquatic toxicitydata are available which can be used for read across.

Hypothesis: Maltol has similar aquatic toxicity potential as the read-across sourceEthyl Maltolasboth substances have the same backbone and functional group.Therefore, the octanol-water partitioning coefficients (log Kow) of both these substances are considered to give direct indication of their toxicities.

Available information: No experimental data are available for Maltol.For the source chemicalEthyl Maltol,data are available from GLP guideline studies with aquatic invertebrates and aquatic algae (OECD TG 202 and 201, respectively). The EC50 for Daphnia is 27 mg/l and ErC50 and EC10 for algae are 7.2 an 1.8 mg/l, respectively.

In more detail:A Daphniaacute static toxicitytest was performed according to OECD TG 202 and in compliance with GLP (Symrise, 2001). In this static study, daphnids were exposed to nominal test substance concentrations of 0 (control), 10, 20, 40, 80, and 160 mg/L for 48 hours under static conditions and in a closed system. TOC-analyses performed at the start and at the end of the test showed >90% recovery of the nominal concentration. The stability of the substance is expected to be fairly stable because the substance does not contain hydrolysable groups, has a low vapour pressure and high water solubility. In addition at this Daphnia EC50 value the concentrations in the algae test is fairly stable. Therefore the TOC analysis are sufficiently reliable and can be used to show analytically stable concentrations.  

An algae toxicity testwas performed in accordance with OECD TG 201and in compliance with GLP. In this study, freshwater algae (P. subcapitata) were exposed to the substance at nominal concentrations of 0 (control), 1.0, 3.2, 10, 32 and 100 mg/L for 72 hours. The concentration and stability of the test item in the test preparations were verified by chemical analysis at 0 hours and from the pooled replicates at 72 hours. The geometric mean measured test concentrations were determined to be 0.21, 0.77, 2.9, 14 and 66 mg/L. Under the conditions of the test, the test item gave an ErC50 and ErC10 of 7.2 and 1.8 mg/L (based on geometric mean measured concentrations), respectively.

Target chemical and source chemical(s)

Chemical structures of the target chemical and the source chemical are shown in the data matrix, including physico-chemical properties and available ecotoxicological information.

Purity / Impurities

Both Maltol and Ethyl Maltol are mono-constituent substances with purities close to 100%. Maltol nor Ethyl Maltol contains any impurities that are considered to impact the assessment of aquatic toxicity from read across.

Analogue approach justification

According to Annex XI 1.5 read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group

Analogue selection: For Maltol the analogue Ethyl Maltol was selected for read-across because it shares the same structural backbone and identical functional groups.

Structural similarities and differences: Maltol (target) andEthyl Maltol(source) have the same cyclic backbone with an ether bond to which a ketone and an alcohol moiety are attached at identical positions. The only difference between the substances is that Maltol is methylated at its 2-position whereas Ethyl Maltol is ethylated at its 2-position.

Bioavailability:Maltoland ethyl Maltolhave similar bioavailability based on the similarity in chemical structures, physico-chemical properties and environmental fate parameters. Both substances are solids with comparable molecular weights. Both substances are water soluble (>>1000 mg/L), log Kow values of <3 and near identical vapour pressures.

Reactivity: Due to the close structural resemblance and identical reactive groups, the reactivity is considered similar.

Uncertainty of the prediction:There are no uncertainties other than those already discussed above. A conversion is not considered necessary the slightly lower molecular weight of Maltol indicates slightly higher toxicity values, the values of Ethyl maltol are therefore considered conservative.

Conclusions for hazard assessment

For Maltol no aquatic toxicity information is available. Therefore information is retrieved from the close structural analogue Ethyl maltol:The EC50 for Daphnia is 27 mg/l and ErC50 and EC10 for algae are 7.2 an 1.8 mg/l, respectively. The same values can be used for Maltol.

Final conclusion on hazard: For Maltol the EC50 for Daphnia is 27 mg/l and ErC50 and EC10 for algae are 7.2 an 1.8 mg/l, respectively.


Data matrix presenting the aquatic toxicity information for Maltol, which are derived from Ethyl Maltol

Common name


Ethyl Maltol

Chemical name



Chemical structures


CAS no






Reach registration

Before 2018 deadline

Before the 2018 deadline

Empirical formula



Molecular weight



Physical state



Log Kow

2.3 (exp.)

2.9 (exp.)

Water solubility, mg/L

5791 (exp.)

9345 (exp.)

Vapour pressure, Pa



Aquatic toxicity



Aquatic invertebrates EC50 in mg/L

Based on read-across from Ethyl Maltol



Aquatic algae

72-h ErC50 in mg/L

72-h ErC10 in mg/L


Based on read-across from Ethyl Maltol