Heavy metal toxicity has proven to be a major threat and there are several health risks associated with it. The toxic effects of these metals, even though they do not have any biological role, remain present in some or the other form harmful for the human body and its proper functioning. They sometimes act as a pseudo element of the body while at certain times they may even interfere with metabolic processes. Few metals, such as aluminium, can be removed through elimination activities, while some metals get accumulated in the body and food chain, exhibiting a chronic nature. Various public health measures have been undertaken to control, prevent and treat metal toxicity occurring at various levels, such as occupational exposure, accidents and environmental factors. Metal toxicity depends upon the absorbed dose, the route of exposure and duration of exposure, i.e. acute or chronic. This can lead to various disorders and can also result in excessive damage due to oxidative stress induced by free radical formation. This review gives details about some heavy metals and their toxicity mechanisms, along with their health effects.

Industrialization and urbanization have led to the release of increasing amounts of heavy metals into the environment. Metal ion contamination of drinking water and waste water is a serious ongoing problem especially with high toxic metals such as lead and cadmium and less toxic metals such as copper and zinc. Several biological materials have attracted many researchers and scientists as they offer both cheap and effective removal of heavy metals from waste water. Therefore it is urgent to study and explore all possible sources of agrobased inexpensive adsorbents for their feasibility in the removal of heavy metals. The objective was to study inexpensive adsorbents like various agricultural wastes such as sugarcane bagasse, rice husk, oil palm shell, coconut shell, and coconut husk in eliminating heavy metals from waste water and their utilization possibilities based on our research and literature survey. It also shows the significance of developing and evaluating new potential biosorbents in the near future with higher adsorption capacity and greater reusable options.

Bladder cancer is a major health-care concern. A successful treatment of bladder cancer depends on its early diagnosis at the initial stage. Genetic instability is an essential early step toward the development of bladder cancer. This instability is found more often at the chromosomal level than at the nucleotide level. Microsatellite and chromosomal instability markers can be used as a prognostic marker for screening bladder cancer. Bladder cancer can be distinguished in two different categories according to genetic instability: Cancers with chromosomal level instability and cancers with nucleotide level instability. Deoxyribonucleic acid (DNA) mismatch repair (MMR) system and its correlation with other biologic pathway, both are essential to understand the basic mechanisms of cancer development. Microsatellite instability occurs due to defects in DNA MMR genes, including human mutL homolog 1 and human mutL homolog 2. Chromosomal alterations including deletions on chromosome 3, 8, 9, 11, 13, 17 have been detected in bladder cancer. In the current review, the most recent literature of genetic instability in urinary bladder cancer has been summarized.

Analysis of groundwaters from the Makutuapora aquifer in the Dodoma region of central Tanzania has revealed a relationship between mineral-water interactions, water chemistry, bedrock geology, and microbiology. Groundwaters were slightly alkaline (pH 6–7.8) and essentially Na-Ca-HCO 3 -Cl, with minor K, Mg, F, and SO 2− 4 . Variations in water chemistry, particularly Ca/Na and Mg/Ca, ratios are related to the progressive alteration of feldspars and ferromagnesium minerals. The constant Na/Ca and Mg/Ca ratios noticed over mature aquifers and wells indicates that a steady-state is attained between aluminosilicates and groundwater. While erratic Fe/Mg and Na/K ratios denote a more open system or rather a greater diversity in minerals hosting these elements participating in mineral-water reactions. In places total concentrations of Fe, Mn, and Al can each exceed 1 mg l −1 with most of the metal held in particulate form (> 0.45 μm). The increase in metals suggests an imbalance in the steady-state reactions between magmatic minerals and leachate, possibly related to microbial activity. Fifty percent of the groundwaters were contaminated by significant numbers of thermotolerant coliforms indicating considerable risk of contamination by faecal pathogens. Numbers of faecal coliforms were positively correlated with K, Na, NO 3 − , PO 4 3− and BOD. Groundwater chemistry also affected the activity of the indigenous microbial community. Microbial biomass appeared to be unaffected by differences in groundwater chemistry. The numbers of selected physiological bacterial types (e.g. organisms contributing to the nitrogen and sulphur cycles) and the range of protist morphotypes, isolated from the tropical groundwater systems, were broadly similar to those found in temperate groundwater. Total concentration of metals such as Al, Fe, Co and Mn certainly exceed levels at which these metals could be considered toxic although if these metals are present in non-labile forms (as suggested by other studies) then the potential toxicity would be negligible. At present the major concerns for health are high seasonal salinities in the groundwaters and high faecal contamination.

Any foreign chemical substance that is unusually present within an organism or is unexpectedly found in the environment at a higher concentration than the permissible limits can be termed a xenobiotic or a pollutant. Such substances include carcinogens, drugs, food additives, hydrocarbons, dioxins, polychlorinated biphenyls, pesticides or even some natural compounds. Pollutants are known for their higher persistence and pervasiveness, and along with their transformed products, they can remain in and interact with the environment for prolonged periods. In this article, the classification of such substances based on their nature, use, physical state, pathophysiological effects, and sources is discussed. The effects of pollutants on the environment, their biotransformation in terms of bioaccumulation, and the different types of remediation such as in situ and ex situ remediation, are also presented.