0731-8898/18/$35.00 © 2018 by Begell House, Inc. www.begellhouse.com 183 Detrimental Effects of Heavy Metals in Soil, Plants, and Aquatic Ecosystems and in Humans a Lecturer, Petroleum Engineering Department, Uttaranchal Institute of Technology, Uttaranchal University, Dehradun, India; b Lecturer, Petroleum Engineering Department, Uttaranchal Institute of Technology, Uttaranchal University, Dehradun, India; c Veterinary Ofcer, Animal Husbandry Department, Kotalisain, Pauri, Garhwal, Uttarakhand India *Address all correspondence to: Ankur Jaiswal, E-mail: ankur16satya@gmail.com ABSTRACT: Environmental pollution has posed a major threat to fora as well as fauna for the past few decades. In- dustries release efuents into the environment which act as the major source of pollution. The hazardous efects of heavy metals released from these industries impact the soil and due to bioaccumulation of these compounds in the food chain, they ultimately result in a serious human health hazard. The concentration of metals like chromium (Cr), lead (Pb), nickel (Ni), cadmium (Cd), zinc (Zn), titanium (Ti), cobalt (Co), and several others in plants as well as in aquatic animals is above permissible limits according to the World Health Organization (WHO) and the Federal Environmental Protection Agency (FEPA) guidelines. This is why we need to prevent the aquatic ecosystem and human health from detrimental efects. In this review we will be discussing the harmful efects of these metals on soil, plants, aquatic ecosystems, and human health. Journal of Environmental Pathology, Toxicology and Oncology, 37(3):183–197 (2018) I. INTRODUCTION Heavy metals are among the main sources of pollu- tion in the soil as well as in the atmosphere. Contam- ination and accumulation cause major issues because of toxicity, nonbiodegradable properties, abundant sources, and cumulative behavior. 1 Soil pollution by heavy metals is mainly due to miscellaneous metals like copper (Cu), cadmium (Cd), nickel (Ni), chro- mium (Cr), zinc (Zn), and lead (Pb). 2 A few heavy metals, like iron (Fe), zinc (Zn), calcium (Ca), and magnesium (Mg), within permissible limits, are sug- gested to be of bioimportance for humans and are recommended in the diet because they have health value. In contrast, metals like arsenic (As), cadmium (Cd), lead (Pb), and methylated forms of mercury (Hg) are documented to have no known biological importance in human physiology and biochemistry, and intake of these metals even at very low amounts can be noxious to humans. 3 These heavy metals im- pose baneful efects on soil microfora and fauna, al- tering population size, population diversity, and all activity of the soil microbial population. 4 Increased concentration of heavy metals due to anthropogenic activities is a major concern. Plants are much afected by chemical pollution, particu- larly in contaminated soils. 5 Elevated Pb concentra- tion in soils can reduce soil efciency, but very low Pb concentration can inhibit biological processes like photosynthesis, mitosis, and transpiration, with adverse outcomes such as leaves becoming dark green in color, drooping of older leaves, reduced foliage, short brown leaves, and short brown roots. 6 The higher concentration of metals taken up by plants from soils places the food chain in severe jeop- ardy. 7 Consumption of heavy metals by plants and consequent accumulation in the food chain is a dan- ger to human health. The intake of food contaminated by heavy metals can severely drain the body of key nutrients, leading to intrauterine growth retardation, lowered immunological defenses, elevated upper gastrointestinal cancer rates, and malnutrition-related disabilities. 8 Agricultural runof containing heavy metals enters the aquatic environment, causing dele- terious efects on aquatic fora and fauna. The current study reviews the deleterious efects of heavy metals on soil, plants, aquatic ecosystems, and humans. II. EFFECTS ON SOIL Soil pollution due to heavy metals is an alarming situation in industrialized regions of the world. 9 Ankur Jaiswal, a,* Arpit Verma, b & Pallavi Jaiswal c