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Br J Ind Med. Jul 1960; 17(3): 190–200.
PMCID: PMC1039179
A Study on the Acute Toxicity of the Tri-aryl Phosphates Used as Plasticizers
H. F. Bondy,* E. J. Field, A. N. Worden, and J. P. W. Hughes§
*Coalite and Chemical Products Limited.
Department of Pathology, University of Durham.
Nutritional Research Unit, Huntingdon.
§Albright and Wilson Ltd.
Abstract
Paralysis in man and the domestic fowl caused by “ToCP” (tri-cresyl phosphate, tri-tolyl phosphate or TTP) is reviewed, and the search for a non-toxic plasticizer derived either from TTP or tri-xylenyl phosphate (tri-dimethylphenyl phosphate or TXP) is described. It had been previously shown that the ortho-tolyl esters are toxic but we found that their removal does not make the mixture non-toxic. The meta- and para-tolyl esters were known to be free from toxic effects and the 2: 4 and 2: 5 dimethylphenyl esters were equally shown to be non-toxic except in massive doses. We confirmed that the tri-ortho-ethylphenyl ester was non-toxic, but found the mono- and di-ortho-ethylphenyl phosphates to be highly toxic. We showed that TTP made from phenols with all the ortho-cresol and ortho-ethylphenol removed is non-toxic.
With TXP, however, elimination of all ortho-cresol and ortho-ethylphenol from the raw materials does not result in a non-toxic plasticizer. Tri-ortho-n-propylphenyl phosphate was shown to non-toxic but esters containing one or two ortho-propylphenyl groups are toxic.
The toxicity of the ortho-tolyl, ortho-ethylphenyl and ortho-propylphenyl groups is much reduced in the presence of the 3: 5-dimethylphenyl group. This influence is greatest in mono-ortho-propylphenyl-di-3: 5-dimethylphenyl phosphate which is non-toxic in five consecutive daily doses of 500 mg./kg. body weight.
The removal of all ortho-cresol, ortho-ethylphenol and ortho-propylphenol from the raw material results in a non-toxic product which we termed non-toxic plasticizer “NTP”. This has been fed in various doses to a variety of mammals and a large number of chickens in short term tests without toxic effects.
Our experiments showed that tri-meta-ethylphenyl phosphate is non-toxic but tri-para-ethylphenyl phosphate is highly toxic. The mixture from which NTP is made contains 10% of para-ethylphenol. Based on chemical statistics the tri-para-ethylphenyl ester can be present only in minute quantities, and we have shown that esters containing one or two para-ethylphenyl groups are non-toxic. An ester with a methyl group in the ortho, and an ethyl group in the para position in the same benzene nucleus (tri-2-methyl-4-ethylphenyl phosphate) we showed, surprisingly, to be non-toxic.
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