Effects of Pesticides on Aquatic Organisms in The Mediterranean Coast of Egypt

Introduction

Over the last two decades of the twentieth century, the use of pesticides has seen a significant increase in several countries worldwide, including Egypt. One common usage of pesticides is in transformers, electrical equipment, and various industries, leading to widespread PCB contaminations at the Alexandria Harbor (Barakat et al., 2002). The presence of organochlorine pesticides (OCPs) as persistent organic pollutants (POPs) has become a major environmental concern, attracting attention from environmental scientists and the general public (Jiang et al., 2009; El Nemr et al., 2003, 2005, 2011, 2012, 2013). In the past, OCPs were among the most extensively used pesticides globally before the 1970s (Wong et al., 2005). Due to their high chemical stability, poor water solubility, and low vapor pressures, OCPs are commonly referred to as persistent organic pollutants (Bouwman, 2004; Darko et al., 2008).

Organochlorine Pesticides and Their Environmental Impact

Out of the 21 POPs marked for phase-out and elimination, 14 are organochlorine pesticides, including DDT, aldrin, endrin, dieldrin, chlordane, heptachlor, hexachlorobenzene (HCB), mirex, toxaphene, alpha hexachlorocyclohexane, beta hexachlorocyclohexane, chlordecone, lindane, and pentachlorobenzene (Stockholm Convention, 2001, 2009), despite being banned from production and usage (Guruge and Tanabe, 2001; Iwata et al., 1994). These compounds are known to act as environmental hormones, disrupting the reproductive cycles of humans and wildlife (Colborn and Smolen, 1996). OCPs have been found widespread in various environmental media, such as soil, water, suspended particulate matter, sediment, atmosphere, and organisms (Cai et al., 2010; Liu et al., 2008). Non-point soil sources contribute to the spreading of OCPs into aquatic environments through runoffs. OCPs' properties, such as low-water solubility and high hydrophobicity, enable them to be readily sorbed onto suspended particulate matter, eventually depositing into river and marine sediments (Yang et al., 2005).

The Role of Soil and Sediments

Soil and sediments play a crucial role in the global distribution and fate of POPs. They have a large retention capacity and can re-emit these pollutants into the environment as a secondary source. Under favorable conditions, bound-OCPs are released from particles into the water (Barra et al., 2005; Zheng et al., 2009). This interaction between sediments and water is now considered a major route of exposure for many species (Zoumis et al., 2001). Even at low doses, OCPs can cause biologically toxic effects on ecosystems in the aquatic environment (Crisp et al., 1998), posing a potential hazard to human beings through aquatic food. Studies have indicated that OCPs may interfere with the normal functioning of the endocrine system in both humans and wildlife (Colborn and Smolen, 1996; Xue et al., 2005).

The Impact of Polychlorinated Biphenyls (PCBs)

Among the well-known POPs are the polychlorinated biphenyls (PCBs), which consist of 209 congeners, each containing two benzene rings and one to ten chlorine atoms (Hutzinger et al., 1974). PCBs possess high lipophilicity, thermal stability, and low flammability (De Voogt and Brinkman, 1989). The degree of lipophilicity increases with higher chlorination levels, resulting in varying levels of bioaccumulation potential (Hawker and Connell, 1988). These compounds have been detected in various environmental compartments worldwide, and they tend to bioaccumulate within food chains (Lundgren et al., 2002). Monitoring all 209 congeners can be highly cost-prohibitive, but detecting significant levels of specific PCB congeners can still provide valuable information due to the high correlation among many of them.

The Mediterranean Coast of Egypt

Egypt's Mediterranean Coast stretches for approximately 1050 km from Rafah in the east on the Sinai Peninsula to Sallum in the west, making it one of North Africa's longest Mediterranean shores. Unfortunately, the Mediterranean Sea faces significant anthropogenic pressure due to various inputs, including industrial discharges, sewage effluents, stormwater drains, shipping activities, spillages, river inflows, atmospheric fallout, coastal activities, and natural oil seeps (UNEP, 1984). Additionally, the coast is characterized by the presence of Egypt's four northernmost lakes.

Investigating the Distribution of PCBs and OCPs along the Egyptian Mediterranean Coast

This study aims to determine the concentrations of polychlorinated biphenyls and organochlorine pesticides in surface sediments along the Egyptian Mediterranean Coast, spanning from El-Sallum to El-Arish. The objective is to understand the horizontal distribution of these compounds and evaluate their potential effects on aquatic organisms.

Conclusion

In conclusion, the increased usage of pesticides and the presence of persistent organic pollutants like PCBs pose a significant environmental concern in Egypt, particularly along its Mediterranean Coast. These substances can have adverse effects on ecosystems and disrupt the reproductive cycles of both humans and wildlife. Understanding the distribution and impact of these pollutants is crucial for implementing effective strategies to mitigate their harmful effects and protect the environment and public health. By conducting comprehensive studies and monitoring, we can take proactive steps towards a cleaner and healthier ecosystem along Egypt's Mediterranean shores.

References

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