Lead Toxicity and Its Effect on Food Chains and Remediation Techniques (Literature Review)

Abstract

The purpose of the study was to review the most recent findings related to lead toxicity for plants, animals and humans. It is stated that the highest potential belongs to biological techniques and the most up-to-date lead phytoremediation technologies. Results and discussion. Lead is one of the most toxic heavy metals which frequently occurs in the environment. Various quantitative indices are used to assess lead toxicity at trophic levels of a food chain, including the levels of lead absorption by plants. Hyperaccumulating plants can accumulate more than 1000 mg/kg of the metal. Higher lead concentrations are connected with fruit plants. Lead transport in animals is done through the blood circulatory system, whereby bones are the main lead absorbers (~ 90%), where lead replace calcium and reduces the bone mineral density. Lead poisoning in humans most frequently results from peroral intake and absorption through the gastrointestinal tract. The main process of lead transport from the gastrointestinal tract to various body tissues is conducted via erythrocytes, where lead binds to hemoglobin. The half-life of lead in blood and soft tissues has been estimated as 35 and 40 days, respectively. Lead may stay in the bones up to 30 years; its concentration rate in the teeth and bones increases with age. Over 95% of lead deposit in the skeleton represent an insoluble phosphate. The biological half-life of lead in children is significantly larger than in adults. The total lead load on skeleton makes 80-95% in adults and around 73% in children. Lead toxicity primarily targets the human central nervous system, and child exposure to high amounts of lead from the environment, particularly in the case of anemia, entails low intelligence and movement disorders. Mothers can transmit lead to fetus or infants during breast-feeding. There are various processes that seek to reduce the overall lead concentration and accumulation in the food chain. Out of those, the most effective are biological techniques of lead remediation from contaminated resources. They include phytoremediation and microbiological treatment. The first option reduces lead mobility in the root zone of plants through complex formation. The second option reduces lead availability in the environment via employing local microorganisms. Both options are a natural, safe, efficient, and environmentally friendly technology which implies cost-effective operation and represents no threat to the environment and health. However, a high potential is detected in biotechnological and genetic approaches, such as genomics, metagenomics, metabolomics, proteomics, transcriptomics, nanoparticles, and isotope probing. These are the most up-to-date technologies for lead phytoremediation. The use of omics approaches implies identifying candidate genes for an efficient lead removal, diverse phylogenetic research into the sequence of genes and proteins that control lead bioremediation and genetically modified plants cultivation via transgenesis, which are able to restore various wastewaters, contaminated lands, and can be beneficial for practical application in bioremediation. Conclusion. The most recent research and development in the field of nanosciences provide access to even more efficient and stable approaches to remediation that are being successfully applied in cleaning soils, deposits, solid waste, and wastewaters