Heavy metals had taken a great attention in scientific studies throughout the past years. In this generation, the amount of toxic materials found in land and water as well as in air has increased drastically. Constant development on modern technology depends on usage of heavy metals. Incorporated with this, heavy metals have major disadvantages of being toxic and having a long half-life. ( Godt, Scheidig, and Grosse-Siestrup et al, 2006; Gunduz and Akman, 2012; WHO, 1995; WHO, 2004) Cadmium, chromium and lead, among other heavy metals are known to be dangerous pollutants in our environment.
Surface finishing and metal deposition are the important processes of electroplating industry which commonly use nickel, copper, zinc and chromium. .Wastewater generated from them release substantial quantity of heavy metal ions which leads to heavy metal pollution. In industrial,
Hexavalent chromium (Cr (VI)) is widely used in various process industries such as leather tanning, pigments and paints, mining, textile dyeing, electroplating, pulp and paper, aluminum conversion coating operations etc. It is a toxic heavy metal often existing in the industrial waste stream. Cr (VI) is known to be a strong oxidant and an acute carcinogen . Therefore the removal of Cr (VI) from waste streams is essential to protect environmental health. The permissible level of Cr (VI) for discharge into surface water is 0.1 mg/L and portable water is 0.05 mg/L [2,3].
Although metals like zinc, iron, manganese and copper are essential for bacterial metabolism (3), their intracellular concentrations must be carefully regulated as their imbalances will be detrimental to cellular integrity. Metals like iron, arsenic, copper, chromium, cadmium, selenium, uranium and several other heavy metals pose significant toxicity to bacteria. For example, they promote oxidative stress and produce reactive oxygen species (ROS) that damage DNA causing mutations and maybe cell death, even in smaller concentrations (4, 5). To protect themselves from metal intoxication, bacteria rely on several mechanisms, including the use of efflux pumps that extrude metals, use of proteins that change the oxidation states of metals, and proteins that bind metals either intracellularly or extracellularly and reduce their toxic effects (6). In addition, mobile genetic elements also play an important function in bacterial response to different environmental challenges, including heavy metal stress (7,
Heavy metals concentrations in aquatic ecosystems are usually monitored by measuring their concentrations in water, sediments, and biota (Oguzie, 2003). Pollution by heavy metals is a serious problem due to their toxicity and ability to accumulate in the biota (Islam and Tanaka, 2004). Metal pollution has a harmful effect on biological systems and does not undergo biodegradation and accumulated in living organisms, thus causing various diseases and disorders even in relatively lower concentrations (Pehlivan et al., 2009). A substantial level of heavy metals causes the major hazard to the environment and accumulates in the ecosystem through two major paths; the first path
Human activities, such as mining, industrial and domestic waste water and sludge, fertilizers and pesticides application to field, also atmospheric deposition are the main sources of heavy metal contamination in plants . Metal contamination of agricultural
Route of exposure : Ingestion, inhalation, dermal and injection 3. age, Sex, Health, Environmental factors and Individual characteristics Heavy metals : It refers to any metallic chemical element which has a high density and poisonous at high concentrations. Such as mercury, cadmium, arsenic, chromium, thallium, and lead. Heavy metals cannot be degraded to a small extent they enter our bodies via food, drinking water and air. Some heavy metals like copper, selenium and zinc are essential to maintain the metabolism of the human body but at higher
Chromium (Cr) is one of the known environmental toxic pollutants in the world which is from group VIII element of the first transition series and has a hard brittle gray transition metal with atomic number 24 and relative atomic mass 51.99 g/mol. Chromium is a naturally occurring element found in rocks, animals, plants, and soil. It can exit in several different forms and the most common forms are chromium, chromium (III) and chromium (IV). The major industrial application of chromium include the processes for making steel, chrome plating, dyes and pigments, leather tanning operations, and wood preserving (Guertin, 2004). According to the Agency for Toxic Substances and Disease Registry ATSDR, (2012) Chromium can be found in air, soil, and
INTRODUCTION Heavy metal pollution in the environment has become a serious issue globally. Heavy metals such as cadmium, chromium and lead, have been found to be present in amounts higher than the natural level in the environment due to anthropogenic activities. Those industries which utilize these metals, such as the semiconductors, battery manufacturing, metal plating and paint, significantly contribute to the pollution loading in the environment (1–3). The indiscriminate discharge of chromium metals into water resources causes serious health hazards to humans and environment because of their toxicity. Chromium exists in trivalent form and hexavalent form in aqueous systems.
The specific branch of science that deals with these environmental contaminants is called Toxicology. To be precise, toxicology deals with the study of poison, that is any particular substance that causes adverse effects to living organisms upon exposure (Hodgson, 2004). There are many characteristics and principles that define heavy metals. To simplify