Research SectionClinical, biochemical and neurobehavioural studies of workers engaged in the manufacture of quinalphos
Introduction
Quinalphos (O,O-diethyl, O-2 quinoxalinyl phosphorothioate) (QP) is a broad spectrum contact and stomach insecticide and acaricide. It is manufactured in India with an installed capacity of 3500 metric tonnes and its production in 1995–96 was to the tune of 2382 mT (Anonymous, 1997). It is widely used for crops such as vegetables, fruits, cotton, groundnuts, cereals and rice. It is also exported in large amounts, although it is banned in some countries.
Quinalphos is manufactured from o-phenylenediamine (OPD) in three successive steps. First, OPD is dissolved in water, followed by adding glyoxalic methyl hemi-acetal (GMHA) with stirring. It is kept at normal temperature for 4–5 hr and centrifuged to obtain wet cakes of 2- hydroxyquinoxaline (2-HQ). The wet cakes are dried in a tray drier. The dried cakes of 2-HQ are made into a slurry in xylene and refluxed with sodium hydroxide to obtain the sodium salt of 2-HQ. After removal of the water layer from the reaction mixture, xylene is distilled off and acetone is charged. This mixture is reacted with diethyl thiaryl phosphorocyanide (DETCN) at 60°C for 8 hr to prepare quinalphos.
After completion of the reaction, acetone is distilled out and xylene is charged. This is washed with alkali solution and the organic phase is separated. Xylene is distilled out leaving technical quinalphos in the flask. All these processes are mechanical and conducted in controlled conditions of temperature and humidity, etc. The plant is situated in large tin sheds without adequate ventilation.
The present study of workers exposed to a mixture of different raw materials, by-products and quinalphos was undertaken to assess the health risk associated with the manufacture of quinalphos.
Section snippets
Materials and Methods
All the 59 subjects exposed directly during manufacture in a production unit, and 17 control subjects who were not engaged in the manufacture or handling of QP but were employed as tea vendors, roadside hawkers, etc., were studied for the following variables at the same time, that is within a period of 10 days. The lower number control subjects is because only a small number of subjects could be found around the manufacturing unit who were not directly or indirectly exposed to any OP
Results
The exposed and control subjects were statistically similar in respect of age, work history, physical activity at work, sex, social characteristics and use of cigarette, alcohol, etc. (Table 1). The higher percentage of graduates among the control group may be because individuals with university degrees seek white collar jobs which are scant, and are often forced to take self-employment ventures for economic reasons. All the study subjects were involved in moderately heavy physical work.
Discussion
Subjects exposed to QP during manufacture suffered from alterations in the function of the central nervous system. These manifested as decrements of higher functions of the brain and the involvement of motor system.
Delayed mixed sensorimotor peripheral neuropathies have been reported after acute exposure to mipafox, trichlorphos, phytosol and tamaron (Bidstrup et al.,1953; Hierons and Johnson,1978; Jedrzejowska et al., 1980; Senanayake and Johnson, 1982). Chronic exposure to tri-o-cresyl
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