# Remediation of Metal/Metalloid-Polluted Soils: A Short Review
## 3 Toxicology
### Health Impacts Over Short, Medium, and Long Term  
The high amounts of these elements in soil lead to the deterioration of agricultural land, eutrophication, and the absorption of toxic substances. Direct effects of contamination are a reduction in the quality of agricultural soils, including phytotoxicity at high concentrations, the preservation of soil microbial processes, and the transfer of zootoxic elements to the human diet [35]. The health of living organisms is damaged, especially in the long term. The principal effects on health can be reduced growth and development, cancer, organ damage, nervous system damage, and, in extreme cases, death [36]. Toxicity depends on the type and form of the element, dose, route of exposure, age, genetics, and nutritional status of the exposed individuals [37]. The United States Environmental Protection Agency (EPA) establishes limits for some heavy metals and metalloids; surpassing these values has toxic effects on human health [38]. It is possible to summarize the principal effects of the most toxic metals/metalloids when the admissible concentration is exceeded:  
* Chromium (Cr): it is found in the environment in different oxidation states (\(-2\) to \(+6\)), but the most stable forms are trivalent (III) and hexavalent (VI). Chromium(VI) is more absorbed than chromium(III) by the human body through inhalation, ingestion, and dermal contact, due to its high solubility and mobility. Chromium(VI) enters into the cell via a nonspecific anion channel via facilitated diffusion, while chromium(III) enters by passive diffusion or phagocytosis. The main organs that are influenced are the liver, kidney, spleen, and bone. The hexavalent form can easily penetrate red blood cells [39]. The main toxic effects of chromium for humans are ulcers, dermatitis, perforation of the nasal septum, and respiratory cancer. In soil, chromium alters the structure of microbial communities and reduces their growth [40]. * Copper (Cu): this element is essential in many biological processes (oxidation, photosynthesis, and carbohydrate, protein, and cell wall metabolism) [41]. Excessive concentration of copper leads to the formation of free radical species that damage the cell and inactivate some enzymes, threatening the environment, microbes, and human health [42]. In particular, the accidental ingestion of copper may cause nausea, vomiting, and abdominal pain, whereas a prolonged exposure leads to chronic effects, involving the liver and kidneys [36]. In the plants, copper accumulates in the roots, reducing their growth and the ability to absorb other trace elements useful for plant development [43]. * Zinc (Zn): is a trace element essential for all organisms, important in nucleic acid and protein metabolism, in cell growth, division, and function [44]. Excessive concentration in food or potable water may cause vomiting, muscle cramps, and renal damage [45]. In plants, a high concentration of zinc leads to a decrease in growth (both roots and shoots) and development of the plant, chlorosis, alteration in metabolism processes, and induction of oxidative damage [46]. * Cadmium (Cd): has eight stable isotopes, the most common are \({}^{112}\)Cd and \({}^{114}\)Cd. Cadmium forms various complexes with amines, sulfur, chlorine, and chelates. Depending on the form, it has different clinical manifestations and toxic effects. Cadmium interferes with cell proliferation, differentiation, apoptosis, and DNA repair mechanism. The common clinical effects are skeletal demineralization, kidney, and liver problems [47]. Excess accumulation in plants can influence both photosynthesis and respiration, transport, and assimilation of mineral nutrients, affecting plant growth and development [48]. * Lead (Pb): lead poisoning occurs mainly by the ingestion of food and water. It is quickly absorbed into the bloodstream, damaging various systems [49].