Chromium toxicity: Source, distribution, challenges, and remediation

Abstract

Chromium (Cr), a transition metal of significant industrial and environ mental relevance, primarily exists in two oxidation states: the relatively stable Cr(III) and the highly toxic, mobile, and carcinogenic Cr(VI). This chapter provides an interdisciplinary synthesis of Cr’s environmental behavior, toxicity mechanisms, primary sources, and remediation strategies. Naturally found in minerals such as chromite and fuchsite, Cr is released into the environment through both geogenic and anthropogenic activities, most notably from leather tanning, electroplating, pigment manufacturing, textile dyeing, and stainless steel production. Complex redox reac tions, pH-Eh conditions, organic complexation, colloidal transport, and microbial processes control its mobility and speciation. Cr(VI), due to its high solubility and bioavailability, poses acute ecological and public health risks, including oxidative stress, DNA damage, and apoptosis mediated by reactive oxygen species. Human exposure can occur through inhalation, ingestion, dermal contact, and even transpla cental routes, affecting multiple organ systems, including the respiratory, hepatic, renal, immune, and reproductive systems. Ecologically, Cr disrupts plant physiology, microbial nutrient cycling, and aquatic food webs via bioaccumulation and trophic transfer. Case studies from Bangladesh, India, China, Peru, and Brazil underscore the socio-environmental dimensions of Cr pollution, including groundwater contam ination, occupational health risks, and environmental justice concerns. The chapter evaluates both conventional and emerging remediation approaches, such as chem ical reduction, precipitation, adsorption using biochar and activated carbon, micro bial transformation, and phytoremediation, while emphasizing that their efficacy depends on site-specific geochemical and speciation factors. By integrating geochem ical, toxicological, and ecological perspectives, this chapter offers a systems-level understanding of Cr toxicity and sustainable management strategies.