Environmental pollution of heavy metals is increasing day by day and becoming a problem due to the adverse effects it is causing around the world. Heavy metals are those naturally occurring metals that have a high atomic weight and a density. These metals are considered as trace elements because of their presence in trace concentrations. Excessive exposure to a heavy metal affects the normal function of the body either of the plant or of the animal. Some examples of heavy metals that can cause toxicity include lead, mercury, arsenic, cadmium, chromium, cobalt and nickel etc. The toxicity of heavy metal depends on the exposure towards the metal, time and duration of exposure and also the route of exposure. These metals are getting accumulated inside the body of plant and animal and cause severe damage to them. Agricultural soils are generally contaminated by heavy metal toxicity such as Cd, Cu, Zn, Ni, Co, Cr, Pb, and As.
Heavy metal pollution has emerged due to anthropogenic activity which is the main cause of metal pollution. Different industries related to metal, combustion processes, carpet industries, agricultural, pharmaceutical, domestic effluents, lead acid batteries, paints, volcanic eruptions and atmospheric sources etc. are some important reasons by which heavy metal toxicity is increasing day by day. So some important reasons of Heavy metal poisoning are as follows:
Ø Industrial and mining exposure
Ø Air water or soil pollution
Ø Contaminated Foods
Ø Continuous or excessive uptake of Medicines
Ø Coated food containers, plates, and cookware
Ø Ingestion of lead-based paints
Ø Ingestion of insecticides, herbicides, and pesticides
Continuous increasing heavy metal pollution has led to an increase in the mobilization of these elements in the environment and disturbance of their biogeochemical cycles. Contamination of aquatic and terrestrial ecosystems with toxic heavy metals is an environmental problem of public health concern. Heavy metals accumulate in the environment and consequently contaminate the food chains. Plants are contaminated by these metals by absorbing the toxic water containing these metals coming from the pollutant agent. These metals are accumulated inside the plant body and disturb all the metabolism of the plant body as enzyme activities, physiology, biochemistry etc. The effects of these heavy metals can be easily seen by the toxicity symptoms like low biomass accumulation, chlorosis, inhibition of growth, photosynthesis, altered water balance, nutrient assimilation, and senescence, yellowing of plant, curling, wilting, etc. When these plants are taken up by herbivores and herbivores are taken up by carnivorous animals, these metals are continuously transferred through the food chain and food web causing harmful effects to them. Atomic Absorption spectroscopy is the most suitable chemical method for determining heavy metals (in soil, water and also in plant).
Heavy metal toxicity symptoms
Heavy metal toxicity symptoms depend on the type of metal causing toxicity, and its duration For example with arsenic and lead exposure, the toxicity symptoms may not show up for two to eight weeks ,however with cadmium poisoning symptoms may arise hours after you’re exposed. Chronic exposure to lower levels of heavy metals may cause symptoms that develop slowly over time. Some common symptoms may include:
Ø Headache Nausea
Ø Muscle pain
Ø Joint pain
Ø Falling into a coma
Heavy Metal Toxicity Treatments
Arsenic, cadmium, chromium, and nickel are important carcinogens causing ulcers and cancer type diseases. Exposure to too much chromium may cause lung and respiratory tract cancer.
Phytoremediation is the unique technique of growing plants in contaminated soil to absorb heavy metals, then harvesting these crops and taking them to an extraction and disposal facility. These plants are called hyper accumulators.
Many other treatment options like physical, chemical, and biological were implied to remediate heavy metal contaminated soil, water, and sediments as thermal treatment, adsorption, chlorination, chemical extraction, ion-exchange, bioleaching etc.
Toxins can be also removed from the body through chelation. Chelation therapy involves chelating agents to remove heavy metals from the body by binding to heavy metal toxin ions and allowing them to be dissolved and excreted in the urine.
Author : Dr. Kanchan Awasthi