Chronic effects of organic pesticides on the aquatic environment and human health: A review

Abstract

Aquatic environment could be termed as the intercommunicating arrangement of water, sediment and biota that provide food for humanity. Aquatic environments have deteriorated substantially due to the accumulation of toxic inorganic and organic pollutants that cause potentially adverse, widespread and detrimental effects on human health. Among the toxic pollutants, pesticides are among the most concerning compounds. Pesticides are applied broadly to restrict insect infestation in agricultural crops as well as to eradicate a variety of pests and disease bearing organisms such as mice, rats, ticks and mosquitoes from human habitats and environments. Among the top ten pesticide-using countries of the world, more than 30 % are in South-Asia. Organochlorine pesticides (OCPs) such as dichloro-diphenyl-trichloroethane (DDT), aldrin, dieldrin and polychlorinated biphenyls (PCBs) are among the most environmentally detrimental pesticides. OCPs can persist for more than 40 years among components of the environment such as soil, water, fish tissues, and other aquatic biotas. Environmental integrity and human health are threatened by over 500,000 tons of OCPs in numerous countries. About 1–5 million cases of intense pesticide toxicity happen annually worldwide, causing approximately 200,000 deaths annually, in part because of bio-accumulation and bio-magnification of persistent pesticides. In aquatic environments, pesticide toxicity causes mortality, reproductive failure, egg shell thinning, suppression of the immune system, and other fish health complications such as excessive slime on fish scales and gills, cancers, tumors and lesions. In humans, pesticide toxicity causes short-term diseases such as skin and eye irritation, nausea, dizziness, headaches, and also chronic impacts such as diabetes, asthma and cancer. This review provides the historical overview with regard to the levels and distribution of organic pesticides in a range of environmental compartments of the Asian region as well as a worldwide perspective. It also presents a comprehensive consideration of chronic effects of pesticides on human health.

Introduction

Aquatic resources (ponds, lakes, rivers, streams as well as oceans) and fisheries are especially precious natural assets. Recognition of aquatic systems along with fisheries has been associated to rising concern about the impact of increased human population and their activity on the aquatic environment. Pesticides are a major group of toxic compounds linked to human exposure that inflict substantial impacts on aquatic environments (Helfrich and Hipkins, 2009).

Any substance or mixture of substances engaged for mitigating, restricting, demolishing or dispersing pests such as weeds, insects, rats, nematodes, mites etc. are referred to as pesticides (Zhang et al., 2011). The worldwide application of pesticides is increasing steadily as a consequence of continually-rising population in need of increased quantities of food. Liu et al. (2002) documented that around one third of the worldwide agricultural products are subject to pesticide application. Cai (2008) reported that if pesticides are not applied, 32 %, 54 % and 78 % production loss of cereals, vegetable and fruits, respectively could be anticipated. Pesticides figure essentially in the health sector beyond their role in agriculture. The most effective and broadly utilized techniques for restricting malaria-bearing insects with insecticides have been reported by World Health Organization (WHO) and described by Elibariki and Muguta (2017). Particularly during improper application, almost all pesticides become severely toxic to the environment as well as to humans. Ubiquitous application and discharge of pesticides is considered among the most common sources of pesticide metabolites in river, sediment and air with threatening ecosystem and human health implications. Environmental pollution originating from pesticides creates severe problems in Asia, Africa, Eastern Europe, Latin America and the Middle East (Sitaramaraju et al., 2014). Organchlorine pesticides like hexachlorobenzene, heptachlor, endrin, dieldrin, aldrin, hexachlorocyclohexane (HCHs) and dichlorodiphenyltrichloroethane (DDTs) are particularly responsible for acute cases of pollution. Organochlorine pesticides (OCPs) are still used, in spite of being banned in most countries (UNEP, 2009). Due to their properties of high lipid solubility (lipophilicity), less aqueous solubility and less polarity, OCPs are capable of bio-accumulating in food chain causing considerable threats to the global environment, and ultimately to humans (Afful et al., 2010). Because of their extended mobility, persistence in the environment and long half-life, OCPs have been found in water, soil sediments and food for decades after their initial application (Abbassy et al., 1999).

Organochlorine pesticides (OCPs) enter the environment through assorted means including spraying and discharging of polluted wastage into disposal areas, as well as from industrial effluents (CDC, 2016). Prior to accumulation in soils and water, airborne OCPs can move into remote areas as influenced by wind (Leadprathom et al., 2009). By this mode of dispersal, OCPs have been observed at hundreds to thousands of miles from their initial point of use (Hung, 2002). Few OCPs are volatile, whereas some can attach to soil or air particles (Smaranda and Gavrilescu, 2008). The metabolites of DDT and dieldrin can persist in soil for years after initially entering food chains by adsorption (Ritter et al., 1995). By the consumption of these polluted foods, both people and animals are vulnerable to the uptake and accumulation of OCPs. Because of their highly lipophilic (fat soluble) characteristics, the risk of the presence of OCPs in fatty foods is enhanced. Above 90 % OCP adulterants have been found in food, particularly in fish (Li et al., 2008).

For the reasons mentioned above, in order to adopt preventive measures towards limiting the application of organic pesticides for ensuring ecofriendly aquatic ecosystems, there is a compelling need to evaluate the distribution of and contamination by organic pesticides in water, sediment, aquatic biota as well as their ultimate chronic effects on human health.