Simulation of hemo- and biochemical toxicities associated with chronic inhalation exposure to 2,2-Dichlorovinyl dimethyl phosphate (DDVP) in Wistar rat
Graphical abstract
Introduction
Dichlorvos, chemically known as 2,2 Dichlorovinyl dimethyl phosphate (DDVP), is an organophosphate (OP) insecticide commonly utilized in Nigeria for pest control in fruit, vegetables, seed and cash crops, as well as livestock and pet animal parasite control (Varo et al., 2003; Binukumar and Gill, 2010; Deka and Mahanta, 2015). DDVP is also used as a fumigant (Williams, 2013). This synthetic insecticide is formulated as aerosol and soluble concentrates to be diluted upon use (Mani et al., 2014). DDVP is liberated into the environment during its manufacture and use, from landfills after disposal, accidental spills during transportation and leakages from storage vessels (ATSDR, 1997).
DDVP is rapidly absorbed in the mammalian body by all routes of exposure. Direct routes of human and animal exposure to DDVP include the oral, respiratory (inhalation) and dermal routes (Okoroiwu and Iwara, 2018). Exposure is most likely to occur in workers of facilities that utilize DDVP such as manufacturing, processing, storage and sale facilities, as well as farm workers (ATSDR, 1997). These facilities are usually poorly ventilated, increasing the probability of exposure via the inhalation route. Personal protective equipment (PPE), which is a means of limiting exposure to this organophosphate (Munoz-Quezada et al., 2017; Garrigou et al., 2020) is not regularly used in Nigeria.
The most common route of exposure and acute toxicity of DDVP in humans and animals is inhalation (Okoroiwu and Iwara, 2018). This route aids immediate delivery of substances into the blood stream because of the large surface area, broad blood supply and very thin alveolar-capillary membrane of the lung (Labiris and Dolovich, 2003). Inhalation thus facilitates a rapid onset of toxicity and DDVP is classified as a class 1B compound (highly hazardous chemicals) (Okoroiwu and Iwara, 2018; Stewart, 2018).
The main toxic effect of DDVP is mediated through non-reversible phosphorylation of acetylcholinesterase in the central nervous system (Wang et al., 2004; Colovic et al., 2013). The mode of action that result in the effects of DDVP toxicity in target organs other than those of the central nervous system, including the liver and kidney is unknown (Bui-Nguyen et al., 2015). DDVP is rapidly degraded by the liver and subsequently eliminated via kidneys (Bui-Nguyen et al., 2015; Oyagbemi et al., 2018), thus, it does not bioaccumulate in body tissues (Okoroiwu and Iwara, 2018). This study focused on the hematological and biochemical toxicities following chronic exposure of male Wistar rats to DDVP for 60 days via the inhalation route. Environmental or Workplace exposure to pesticides is increasingly of concern. The study was therefore designed to simulate varied exposure levels and duration in manufacturing, packaging and retail facilities as well as farm personnel in contact with this organophosphate without adequate PPE. The weight gain of the rats and clinical signs of toxicity were monitored through the period of exposure.
Section snippets
Animals and acclimatization
Sixty age-matched male albino rats (150−180 g) were obtained from the Experimental Animal House of Department of Veterinary Pharmacology and Toxicology, University of Ibadan, Ibadan. The rats were stabilized for two weeks during which they were fed with pelleted commercial rat feed and given portable water, as needed. Experimental animals were grouped into six groups (AF) of ten rats each (n = 10). Group A (control) were exposed to 0% DDVP solution, while rats in Groups B–F were exposed to 20
Body weight and clinical signs
A gradual increase in weight was observed in rats exposed to 0% DDVP, 20 % DDVP, 40 % DDVP, while a concentration-dependent decline in increase was observed in rats exposed to 60 % DDVP, 80 % DDVP, and 100 % DDVP. Significant decline in rate of acquisition of weight increase and eventual loss of weight was recorded in rats exposed to 80 % DDVP by days 40 and 60, while 100 % DDVP by days 20, 40 and 60 compared to non-exposed (control) rats (Table 1). Also, signs of respiratory distress and
Discussion
Inappropriate pesticide usage is on the increase in Nigeria, and it exposes the user/handler to significant health risks and repercussions due to the general non-adherence to PPE use in manufacturing, packaging and distribution facility workers. DDVP is one of the most volatile organophosphates and it is cleared to metabolites which are much more water-soluble compared to the parent compound (Moore et al., 2014; Swaran, 2016). In this study, exposure to DDVP via the inhalation route
Conclusion
This study on chronic exposure of rats to DDVP via inhalation route showed dose-related neuronal injury symptoms, hematological and biochemical toxicities including polycythemia, neutrophilia, thrombocytosis, hepatic and renal derangement accumulating in the ongoing inflammation. Our report emphasizes the hazards of mishandling of pesticide including DDVP and the risks of non-compliance with personal protective equipment use by workers in contact with DDVP. Adequate preventive measures are
Funding source
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The authors do not declare any source of income for the research.
CRediT authorship contribution statement
Kehinde Olusola Awotunsin: Conceptualization, Funding acquisition, Investigation, Data curation, Methodology. Olayinka Ayotunde Oridupa: Conceptualization, Funding acquisition, Methodology, Project administration, Writing - original draft. John O. Ogunsola: Data acquisition, Formal analysis. Ayobami Deborah Obisesan: Data curation, Formal analysis. Adebowale Bernard Saba: Conceptualization, Supervision, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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