ABSTRACT
This chapter observes that the activity of β-galactosidase was insensitive to organic toxicants while being relatively sensitive to heavy metals. Dehydrogenases and hydrolases are the main classes of enzymes which have been considered for toxicity testing in aquatic environments, wastewater effluents, sludges, soils, and sediments. The main problems caused by discharges of toxic pollutants to receiving waters are toxicity to aquatic organisms and restrictions on human use of these waters. Metals may be present in a wide variety of physicochemical forms in aquatic environments, and their speciation has a profound effect on their bioavailability and toxicity to aquatic organisms. Several physical, chemical, and biological factors influence the bioavailability and thus, the toxicity of metals in the environment. These factors include pH, suspended particles, redox potential, water hardness, and organic and inorganic compounds. Several enzyme and microbial assays have been developed and proposed to respond to the need for carrying out rapid and inexpensive toxicity assessment of environmental samples.
