Zinc Diethyl Risk Assessment
Toxicological and Hygienic Risk Assessment of Zinc Diethyl Autooxidation and Hydrolysis Products at Normal Temperature and Air Humidity. Synthesis and Analysis of Physical and Chemical Properties of Zinc Diethyl Transformation Products
Tech Area / Field
- CHE-SYN/Basic and Synthetic Chemistry/Chemistry
3 Approved without Funding
VNIIEF, Russia, N. Novgorod reg., Sarov
- A.I. Burnazyan Federal Medical and Biophysical Center, Russia, Moscow
Project summaryMultiple chemical compounds widely used in various industrial fields and in household are one of the leaders in man-caused affecting the environment and human health. Today there are more than 13 million chemicals known and more than 300 000 chemicals are being handled in the international market.
As the toxicological studies are rather expensive, labor- and time-consuming, only 20% of the potentially hazardous substances manufactured or applied in industry are provided with ecotoxicological data necessary for the assessment of their effect on human health and the environment.
So, for example, there are no detailed data available on the toxicity of organometallic compound – diethylzinc (Et2Zn) and its transformation products that form at normal temperature and air humidity. No hygienic regulations (Maximum Permissible Concentrations and Reference No-Adverse-Effect Exposure) to limit the amount of Et2Zn in workplace air are there in Russian Register of Potentially Hazardous Chemical and Biological Substances.
At the same time Et2Zn is known to be intensively used:
- as a reagent and catalyst in production of practically important chemical compounds and materials based on them:
1) by Et2Zn autoxidation the corresponding organozinc peroxides are obtained;
2) the hydrolysis of the latter substances is used for the synthesis of organic hydroperoxides;
3) Et2Zn-oxygen catalytic system is used to initiate the polymerization of olefins (ethylene, propylene);
4) the binary mixture of Et2Zn with aluminium oxide catalyzes the polymerization of alkylene oxides;
5) [(C2H5)4Zn]Sr, [(C2H5)4Zn]Ca, [(C2H5)4Zn]Ba complex compounds obtained from Et2Zn initiate the polymerization of monomers with the generic formula CH2=CHCOSR;
6) [(C2H5)4Zn]Ca complex initiates the polymerization of styrene, methyl methacrylate and acryl nitrile;
7) Et2Zn-water system is a good catalyst for the polymerization of acetaldehydes, propion aldehyde and trichloroacetaldehyde;
- as a source material in obtaining extra-pure zinc sulfide and selenide, used in semi-conducting and luminescent equipment, for making photocells and photoresistors;
- as a chemical compound applicable for centrifugal separation in production of zinc depleted by 64Zn isotope, the product that is used in fission reactors materials in the USA, Japan and Germany.
The leading companies that produce various metal alkyl compounds and, in particular, diethylzinc are USA Akzo Nobel Chemicals Incorporated and Akzo Nobel Europe.
According to the existing medico-sanitary regulations, each chemical before it is used should undergo a toxicological and hygienic examination, based on the results of which measures are established to guarantee occupational safety at enterprises and to protect humans from adverse effects of the chemicals.
The preliminary toxicity evaluation of Et2Zn solution in liquid paraffin carried out by the SRCR-IB specialists indicated that exposure to large doses resulted in acute lethality in experimental animals (white mice, rats). The reasons for that are acute impairment of blood circulation and gas embolism caused by instantaneous decomposition of Et2Zn while contacting with body’s fluids, and release of gaseous and solid products, as, probably, ethane, ethylene and organic and inorganic zinc-containing substances.
However, in real conditions such effects of Et2Zn are unlikely and are only possible in exceptional cases associated with serious accidents.
Under normal working conditions the presence of airborne Et2Zn per se is practically impossible in view of its high reactivity, and the hygienic conditions at enterprises are obviously determined by the products of Et2Zn reactions with oxygen and moisture. Today there are no sufficient data on the composition of these products; there is no information on their stability in the environment and on their biological effects.
Therefore, studying these chemicals, i.e., identification of their composition, determination of their chemical and physicochemical properties, evaluation of their biological activity, toxicity and risk associated, as well as establishing toxicological and hygienic limits of Et2Zn and its transformation products concentrations in workplace air are actual tasks aimed at prevention of work related injuries and protection of workers’ health.
Within the scope of the Project activities it is supposed:
- to carry out experimental and analytical investigations to precise the list of the basic products of Et2Zn transformation at normal temperature and air humidity;
- to determine distinctive kinetic features of the reactions with Et2Zn in terms of their dependence on the medium nature (solvents), reagents concentrations, temperature, etc., to find the optimal conditions for separation of intermediate and final products of Et2Zn transformation: EtZnOOEt, (EtOO)2Zn, (EtO)2Zn, EtZnOH, EtOZnOH, EtOOZnOH, etc.;
- to perform a controlled Et2Zn oxidation by oxygen, interaction with some organic and inorganic compounds (hydroperoxides, spirits, aldehydes, hydrogen peroxide, water, etc.);
- to determine the basic chemical and physicochemical properties of the above products:
— thermal and photoresistance;
— disproportionation and exchange reactions;
— physical and chemical adsorption on the surface of the target tissues (soft tissues of animals);
— conditions of complexing and associated lowering of chemical and biological activity;
- to conduct experiments with lab animals for comparative assessment of toxicity and risk associated with the compounds resulting from Et2Zn transformation;
- to identify the peculiarities of their biological effects for various routs of entering the body (through the undamaged skin, gastrointestinal tract, eye mucosa and others);
- to identify intoxication differentiation resulting from acute and chronic exposure, to evaluate cumulative features and to predict possible development of intoxication at long-term exposure to low doses of the substances under study;
- to identify and rank the most toxic and hazardous products of Et2Zn transformation;
- to establish toxicological certificates with recommendations for sanitary and hygienic limits of Et2Zn and its transformation products concentrations in workplace air, and to propose a number of practices to prevent work related poisonings and professional diseases associated with handling Et2Zn.
The data obtained as a result of the Project activities will directly contribute both to the basic knowledge of organozinc compounds, and to industrial toxicology, and sanitary and hygienic regulation as to the Maximum Permissible Concentration.
The objectives and goals of the Project completely agree with those of ISTC:
· Studying diethylzinc autoxidation processes to obtain clear idea about the character, mechanism and kinetics of the primary reactions depending on the medium nature, intermediate products and their transformations seems to be necessary both for the development of theoretical chemistry and for variety of applied problems.
· The results of the Project might be used for the development of sanitary and hygienic practices to provide safe occupational environment at enterprises.
· The economic benefits from implementation of the proposals based on the Project outcome are determined by eliminating adverse health effects from hazardous substances and preventing man-caused accidents.
· The combination of RFNC-VNIIEF specialists’ knowledge in the fields of synthesis and chemical kinetics, catalysis, topochemistry, thermodynamics, etc. and SRCR-IB scientists’ expertise in industrial toxicology, and hygienic regulation and balancing of chemical, physical and biological environmental factors will be effectively employed to solve the problems put by.
The experimental basis and high-qualified specialists of RFNC-VNIIEF and SRCR-IB for successful implementation of the Project are available.
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