Environmental Toxicology. Homework 6 - Essay Example

Environment and Toxicology Which contaminant played a role in the origin of the "Madhatter" character in "Alice in Wonderland"?C. Mercury* 2. In terms of dose-response behaviour, selenium is an example ofB. Macronutrient* 3.The increased concentration of an element in an aquatic organism relative to water it lives in, acquired over its life is calledA. Bio concentration* 4.List six uses of lead that make cause exposure to humans.Used in paint and other protective coatingLead acid batteries industriesUse of lead in cosmeticsLead used in hobbies and arts such as firing guns and making ammunitionLead in imported candies from Asia and MexicoLead used in water pipes contaminates drinking water 5.

Tetraethyl lead is the most common form of lead in paints.B. False* 6.Describe the free ion activity model.This model explains the relationship between speciation and bioavailability. The model illustrates the speciation profile of different metals. It explains the bioavailability of that metal in the environment. In addition, it entails modes of preventing the metal from affecting the ecosystem especially by dominating the food chains (Brack, 2011).7. Which dissolved copper species is most toxic to aquatic organisms?C. Cu2+*8.

A water sample consists of the following cadmium species and their percentages of the total cadmium concentration: Cd2+ (36 %); CdHCO3- (14 %); CdCl- (25 %); and Cd (OH) 2 (25 %). What percentage of Cd is toxic to aquatic organisms (only enter the number without a % sign)? 369. Bio magnification is a process typical of most metals.A. True* 10. In its bioavailable form, which element is a neurotoxin?C. Hg* 11. The species of mercury of greatest concern for bioaccumulation and health risks to humans isC.

Methyl mercury* 12. Describe how the solid phase speciation (i.e., chemical form) of lead affects its bio accessibility in the human digestive tract.Bioassessibility refers to the amount of a pollutant that can be dissolved by the digestive fluids. Lead enters the body through either ingestion or inhalation. As much as it can be eliminated, continuous exposure leads to accumulation as well as intoxication. Analysis of waste materials indicates that 40% of lead was present as cerrussite (Brack, 2011).

Cerrussite is a highly bio accessible lead-carrying molecule. However, 65% of lead also exists in the waste in a bio accessible form (Brack, 2011). This shows that lead which does not exist as cerrussite is also high bio accessible. Lead bearing minerals such as sulfur and oxygen make it more bio accessible. Presence of these stable minerals is evident in the stomach and the intestinal phase. The higher the residence of the lead in the gut the higher the bio accessibility.13. Briefly describe the chemical and biological processes by which mercury from a coal-fired power plant enters a lake and makes it way to humans through fish caught and consumed by a fisherman or fisherwoman.

Coal fired power plants emit mercury, which accumulates as sediments. Sulfur reducing bacteria then converts the mercury into methyl mercury. The sediments are then passed into water bodies and into the systems of fishes. Mercury is bio accumulative and hence it is retained in the bodies of the fish. There is a high bio concentration of methyl mercury in these aquatic organisms (Brack, 2011). Fishermen catch the fish and as they consume them, methyl mercury is passed on to them.References Brack, W. (2011). Effect-directed analysis of complex environmental contamination.

Berlin: Springer Berlin.