Zinc, O,O-mixed (iso-Bu), (iso-Pr), (pentyl) phosphorodithioate

Acute Toxicity: oral

Administrative data

Endpoint:

acute toxicity: oral

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Justification for type of information:

REPORTING FORMAT FOR THE CATEGORY APPROACH
Please refer also to the read-across statement attached in section 13

1. HYPOTHESIS FOR THE CATEGORY APPROACH (ENDPOINT LEVEL)
The target and the source substances are structurally similar substances that share the common organometallic core structure consisting of a central zinc metal bonded to four alkyldithiophosphate esters (ligands) by coordinate covalent bonds -Zn[(S2P(OR)2]2. Structural variations between the target and the source substances are related only to the alkyl (R) groups of the alkyldithiophosphate ligands. The substances in this category give thus rise to an (identical) common compound Phosphorodithioic acid moiety that can be released by the breakage of ester bonds and dissociation from the Zinc complex to which the organism would be exposed if the target substance was tested in the toxicity studies. Exposure to the parent compounds (non-transformed constituents) and to the counter alkyl alcohols, possibly released by hydrolysis of P-O bonds – non-common compounds – would not influence the prediction of the (eco)toxicological properties because they are considered to have the same biological targets and to cause the same type of effects through a common underlying mechanism due to the same functional groups (zinc cation, phosphorodithioic cation and aliphatic alcohol anionic moieties). The impurities of the target and the source substances are not expected to impact the prediction because they are identical or, if slightly structural different, belong to the same class of compounds with the same functional groups and their percentages are very low.

2. CATEGORY APPROACH JUSTIFICATION (ENDPOINT LEVEL
The acute toxicity potential of the ZDDP category members is reported to be low (HPV, 2005). The source substances were practically non-toxic in the acute toxicity study with rats (LD50 >3000 mg/kg bw).
Since the main constituents of the target substance are structurally similar to the constituents of the source substances with the same functional groups and the alkyl chain lengths of phosphoroditioate moieties are in the range of the established ZDDP category (C3-C12), the same mode of toxicological action is expected for the target and the source substances. The constituents of the target substance do not possess functional groups associated with other mode of actions or toxicity effects. Toxicokinetic behavior of the constituents of the target substance is expected to be essentially the same as that of the source substance. Based on the results of the oral acute toxicity studies with the source substances and other ZDDP category members, it is evident that the structural dissimilarities – the chain lengths of the alkyl rests – did not result in different strength of the toxicity effects. Even if absorption through GI tract of the category members with shorter alkyl rests and theoretically higher absorption rates (due to the increased water solubility and decreased molecular weights favouring absorption) is higher, their intrinsic properties are essentially the same as the findings in the acute toxicity studies are very similar. The impurities of the target substance are considered not to contribute to the toxicity effects because they are also structurally similar to the impurities of the source substances and consist of substances of simple structure without specific mode of action. Furthermore, their amounts are very low. Therefore, it is predicted that the target substance would possess the same toxicity potential by acute oral exposure as the source substance.

Materials and methods

Test material

Test material information

1

Reference substance name:

Zinc, O,O-mixed (iso-Bu), (iso-Pr), (pentyl) phosphorodithioate

EC Number:

820-225-5

Cas Number:

101747-77-7

Molecular formula:

C12-20H28-44O4P2S4Zn

IUPAC Name:

Zinc, O,O-mixed (iso-Bu), (iso-Pr), (pentyl) phosphorodithioate

Test material form:

liquid

Results and discussion

Effect levels

Sex:

male

Dose descriptor:

LD50

Effect level:

3 100 mg/kg bw

Based on:

not specified

95% CL:

>= 1 800 - <= 5 100

Mortality:

7500 mg/kg: 10/10 rats died 1-2 days after exposure
5000 mg/kg: 9/10 rats died between 1-9 days after exposure
3300 mg/kg: 6/10 rats died 1-2 days after exposure
2200 mg/kg: 2/10 rats died between 1-8 days after exposure

Clinical signs:

Depresson, diarrhea, reduced food intake

Gross pathology:

Survivors had less than normal amounts of body fat. No other changes observed.

Other findings:

not specified

Applicant's summary and conclusion

Interpretation of results:

Category 5 based on GHS criteria

Conclusions:

The rat oral LD50 is 3100 mg/kg in male rats. Sublethal effects of depression, diarrhea, and reduced food intake were observed. Necropsy observations included reduction of body fat, no specific organ toxicity is evident.

Executive summary:

The substance was tested simiar to OECD Guideline 401. The rat oral LD50 is 3100 mg/kg in male rats. Sublethal effects of depression, diarrhea, and reduced food intake were observed. Necropsy observations included reduction of body fat, no specific organ toxicity is evident.