Bio-accumulation of heavy metals in fish tissues is one of some major food hazards.
Heavy metals and contaminants in edible parts of fish results from polluted soils, waters and particular processing techniques such as smoking, roasting, drying and grilling. Level of exposure of heavy metal defines the severity of toxicity and hazards which clearly depends upon time and amount of bio-accumulated toxin.
As some metals are required for the maintenance of healthy metabolism, but the requirement of Cr3+, Fe, Zn, Cu and Se is in very low concentration. Traces of these metals are an essential part of human diet. On the other hand, some metals are highly carcinogenic even at very low concentrations. Heavy metals like Al, Cd, Hg, Ni, Ag, Ba, Pb and Cr6+ has no nutritional importance that is why their small amounts can dangerous for health.
Past few decades are considered important for the aquatic pollution because of increased human activities. Industrial and domestic wastes released into aquatic environment are the major cause of extensive heavy metal addition resulting into aquatic pollution and ultimately health hazards from fish consumption. Different aquatic organisms and the environmental balance of the recipient environment have been devastatingly affected by HMs contamination. In the furtherance to this course, these pollutants have damaging effects on fish by causing bio-accumulation of traces. The fitness of aquatic system can be determined by the health of fish as toxins from the water accumulates in fish and results in the death of aquatic organisms. In the blood and the tissues of fish because of bio-accumulation of heavy metals traces, biochemical parameters and physiological activities can be altered by heavy metals. Protective defense system is developed in organisms to combat with the hazardous properties of non-essential and essential heavy metals which can cause problems like oxidative stress to the body and in long term results into bio-accumulation of toxic heavy metals.
Impacts on human health:
Exposure to heavy metals like lead, chromium, cadmium and mercury is a major health concern for humans and these metals are widely under observation and their impacts on human well-being are frequently revised by World Health Organization (WHO). Humans have been using heavy metals for different purposes for many years, but ingestion in the form of bio-accumulation in the tissue is a greater risk.
The range of health effects of metals includes dementia, neurological disorders, damage to the central nervous system, cardiovascular diseases, increases in systolic and diastolic blood pressure, gastric upset, loss of memory, constipation, nausea, vomiting, listlessness and severe trembling, abdominal pain and faintness, cancer and renal dysfunction. The major health concern of As, Cd, Co, Pb, Ni and Cr is cancer.