The researchers of Nizhny Novgorod Research Institute of Hygiene and Occupational Pathology have examined working conditions and their effect on workers' health at more than 30 industrial plants producing low-density, medium-density, high-density and combined PU. The PU are made by block and form methods with constant and periodic technological process. More than 500 workers at the PU manufacturing plants underwent polyclinic and clinic examination. Experimental tests on evaluation of combined effect of mixture of hazardous chemicals were performed. The chemicals that can be found in workplace air most often (toluylendiisocyanate, triethylenediamine, dimethylethanolamine, dimethylcyclohexamine) were investigated. A system of preventive measures for safe working was elaborated.

PUF is produced by interaction between isocyanates and polyethers/polyesters (with urethane links formation) in presence of water, catalyst, blowing agent, emulsifier and other additional substances (plasticizers, antifire additional substances, dyestuff, stabilizers and others). As a rule, the process of PUF manufacture is mechanized and main stages of this process are automatic. Raw materials are transported in closed communications using various pumps. It was established that hazardous chemical pollution of workplace air is the leading adverse factor at PU and PUF producing industrial plants.

The pollution level depended on degree of technological process perfection. Hazardous chemicals in workplace air were found almost in all stages of technological process, including initial and final stages. Air pollution was often accompanied by adverse physical factors (high and low temperature, noise). Isocyanates and amines play a key role in a mixture of chemicals in workplace air at low-density PU and PUF producing plants. Hazardous chemical compositions in workplace air at others PU and PUF producing plants varied.. Usually the most volatile and nonreactive catalysts, solvents used for equipetment cleaning were found in workplace air. Concentrations of hazardous chemicals in samples exceeded maximum allowable concentrations (MAC) from 9 to 50%. Peak concentrations varied at different plants and time of peak concentrations exposure was up to 10% of working shift time. Results of physiologo-hygienic investigations have shown that labour at some workplaces belong to "middle-hard" and "hard" categories (load-reload operations, raw materials transporting, removing manufactured articles from moulds and so on). Such labour aggravates biological effect of hazardous substances exposure on human. It was established in the process of investigation that the main causes of adverse occupational factors formation are: using imported raw materials without necessary toxicologo-hygienic examinations, imperfection of technological process and equipment, irrational plant lay-out and ventilation, uneffective individual protective equipment. In a number of cases the investigations were conducted at pilot stages technological process and experimental testing new chemical compositions allowed to demand in time for new composition development with using less volatile chemicals. These compositions were recommended for using after testing (PU producing by "secondary blowing"). The same disturbances in health conditions were revealed in more than 500 examined workers. They acquired disorders of respiratory system, vegetative nervous system, skin damages and changes in biological reactivity. Dozens of methods for measurement of hazardous chemicals in workplace air, on skin surface and working clothes were elaborated. It allowed recommending less toxic and less volatile chemicals for PU composition; and less difficult methods for measurement of chemicals concentrations. Investigation of combined effect of toluylendiisocyanate, triethylenediamine, dimethylethanolamine, dimethylcyclohexaneamine on animals shown the summation of toxic effect (on renal system) and allergic effect.

Identical changes in workers' health condition were induced by work environment factors. Clinical symptoms tended to progressing and depended on length of service. Experiments confirmed our supposition that sensibilization to chemicals promoted development of occupational diseases. Special attention should be paid to imported technological facilities. Working conditions were especially unfavourable when such automatic and robot-serviced facilities broke down. Use of imported raw materials without proper toxicologo-hygienic examination leads to decreasing of working safety. For example, dimethylcyclohexaneamine is an effective catalyst using in many foreign compositions. In our institute we have established [2] that it possesses pronounced resorption through skin (7 class of danger) and penetrates easily all types of working clothes (cotton, wool etc.). Working clothes absorbs dimethylcyclohexaneamine and become a secondary source of workplace air pollution [3]. Effective protection of worker's skin is an actual problem until present time. Problems of preventive sanitary inspection are especially important due to enlargement of foreign trade. Basing on these investigations, a system of measures was developed to provide safe working conditions for enterprises where PU was used. The system included: selection of less hazardous raw materials for PU and PUF manufacture, hygienic requirements to industrial plants designing, preventive and current sanitary inspection, including sanitary inspection of individual protective equipetment, strenghthening of sanitary inspection of work environment hazardous factors. These requirements are in basis of many officially issued regulations.

1. Ashirova SA All-Russian conference "Polymer foams, their properties and the fields of use" Book of abstr., Moscow: 1991, 60-61.

2. Ashirova SA, Osipova TV. The VIII All-Russian congress of hygienic and sanitary physicians. Book of abst., vol. II.- Ìoscow: 1996. 12-13.

3. Mironov LA, Egorova GI. ñ All-Russian conference "Polymer foams, their properties and the fields of use" Book of abstr., Moscow: 1991, 62-64.

4. Yurkin IuP, Petrov EA, Eslimov Iu et al. "Technology of manufacture and perspectives of polyurethane foams industry" Book of abstr. Moscow:1989 6-12.

5. Davis A, Heinghington W. Jornal of the society of environmental engineers.- 1997., 16, n. 1, p. 15-17.