Research Section
Clinical, biochemical and neurobehavioural studies of workers engaged in the manufacture of quinalphos

https://doi.org/10.1016/S0278-6915(99)00123-4Get rights and content

Abstract

59 workers exposed to different chemicals during the manufacture of quinalphos, an organophosphate pesticide (OP) and 17 control subjects were studied. Despite similar blood acetylcholinestarase (AChE) levels in both the exposed and control subjects, a significant number of exposed subjects had altered plantar and ankle reflexes. Higher nervous functions such as memory, learning and vigilance were also found to be affected in these subjects. These findings were attributed to chronic low dose combined exposure to different chemicals used/formed in the manufacture of quinalphos. The study raises the doubt that monitoring of AChE alone among subjects engaged in the manufacture of OP pesticides may not be an adequate safeguard as regards to their health.

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

References (19)

  • S Gershon et al.

    Psychiatric sequelae of chronic exposure to organophosphate insecticides

    Lancet

    (1961)
  • S Hestrin

    Reaction of acetylcholine and other carboxylic acid derivatives with hydroxylamine and its analytical applications

    Journal of Biological Chemistry

    (1949)
  • Anonymous

    Statement showing production of technical grade pesticides in India 1992–93 to 1995–96

    Pesticides Information

    (1997)
  • D.S Barret et al.

    A review of organophosphorus ester induced delayed neurotoxicity

    Veterinary and Human Toxicology

    (1985)
  • P.L Bidstrup et al.

    Paralysis following poisoning by a new organic phosphorus insecticide (mipafox): Report on two cases

    British Medical Journal

    (1953)
  • Dacie J. V. and Lewis S. N. (1975) Practical Hematology. Churchill Livingstone,...
  • B.N Gupta et al.

    An investigation of neurobehavioural effects on workers exposed to organic solvents

    Journal of the Society of Occupational Medicine

    (1990)
  • R Hierons et al.

    Clinical and toxicological investigations of a case of delayed neuropathy in man after acute poisoning by an organophosphorus pesticide

    Archives of Toxicology

    (1978)
  • H Jedrzejowska et al.

    Neuropathy due to phytosol (Agritox)

    Acta Neuropathologia

    (1980)
There are more references available in the full text version of this article.

Cited by (47)

  • Gene expression analysis reveals chronic low level exposure to the pesticide diazinon affects psychological disorders gene sets in the adult rat

    2018, Toxicology
    Citation Excerpt :

    Whilst acute OP poisoning is well characterised, the health effects of low level OP exposure remain contentious. Some studies report that lo w level OP exposure is associated with neurobehavioural impairments; workers exposed to quinalphos during manufacturing processes demonstrated a reduction in memory, learning and vigilance (Srivastava, 2000) and sheep farmers exposed to OPs for an average of 23 years, showed reduced performance in mental flexibility, visual working and auditory memory (Mackenzie Ross, 2010). Other studies have reported no association between chronic low level OP use and neurobehavioural performance (Daniell et al., 1992; Rodnitzky et al., 1975; Steenland, 2000) although a recent meta-analysis on 22 occupational OP exposure studies found that memory and attention scores were consistently lower in chronically exposed workers than in unexposed workers (Meyer-Baron, 2015).

  • Reflections on the process of using systematic review techniques to evaluate the literature regarding the neurotoxicity of low level exposure to organophosphate pesticides

    2016, Environment International
    Citation Excerpt :

    This predominantly negative pattern indicates poorer performance in exposed workers relative to controls. The second thing to note is the studies by Srivastava et al. (2000) and Mackenzie Ross et al. (2007) which showed the largest effect sizes. We were able to explore and discuss possible reasons for the differences noted between studies and we undertook meta-analysis with and without the Mackenzie Ross et al. (2007) study included, since it may have been biasing the overall results, but excluding this study did not render the overall findings non-significant.

View all citing articles on Scopus
View full text