Other Heavy Metals - Page 1 of 3

Module 3: Toxicology - Section 10: Other Heavy Metals

TOX 10.1: Introduction

GENERAL OBJECTIVE

By the end of this module

You should have an overview of the general properties of heavy metals.
You should be familiar with some of the common heavy metals; the most important health effects; how to evaluate exposures and what are the legal exposure standards under the HCS Regulations.
You should know where to find further information on these metals..

This introductory page contains links to other pages in this section. These are included for your convenience, both for reference and for revision purposes. It is strongly recommended, however, that you first access the material in its logical sequence, indicated by the "Next Page" link above.

ACTIVITIES:

We will go through the introductory remarks in during the class session.
Work through the exercise after the introduction.

INTRODUCTION:

Heavy metals are those metals which have a relatively high density and are generally toxic or poisonous at low concentrations.

Examples of heavy metals include mercury (Hg), cadmium (Cd), arsenic (As), chromium (Cr), thallium (Tl), and lead (Pb).

Properties of heavy metals that make them potentially hazardous:

Very stable - cannot be degraded or destroyed.
Widespread industrial use result in high ambient emissions from industrial sources and/or contamination of water supplies.
Bioaccumulate causing chronic toxicity and can be measured in body fluids.
Mainly present in alloys or bound to organic materials which alters toxicity.
Reaction with acids forming reactive hydrides and carbonyls which are highly toxic.
Exert biological effects by forming stable complexes with sulfhydryl groups and other ligands.

Bioaccumulation means an increase in the concentration of a chemical in a biological organism over time, compared to the chemical's concentration in the environment. Compounds accumulate in living things any time they are taken up and stored faster than they are broken down (metabolized) or excreted.

Acute effects:

Usually following ingestion of metal containing compounds (e.g arsenic in fish) or inhaling high concentrations of metal fumes (e.g. chrome/nickel in welding) or gaseous metal compounds (e.g. mercury).
Metallic compounds can be measured in blood or urine to confirm the diagnosis of acute poisoning.
Acute effects require immediate supportive treatment and specific treatment such as chelation therapy (e.g lead, mercury).

Chronic effects:

Usually have systemic effects affecting more than one body system but with propensity for certain organ systems such as brain and nerves, kidneys, reproductive organs, fetus. (See Figure on Affinity of chemicals for specific organs.

REFERENCES:

http://www.lenntech.com/heavy-metals.htm
Ladou J. (ed.) Occupational and Environmental Medicine. Chapter 27. Metals.
Rosenstock and Cullen. Textbook of Occupational and Environmental Medicine. Chapter 30. Metals and related compounds.
http://www.osha.gov/SLTC/metalsheavy/

http://www.emedicine.com/EMERG/topic237.htm

Postgraduate Diploma in Occupational Health (DOH) - Modules 3: Occupational Medicine & Toxicology (Basic) by Profs Mohamed Jeebhay and Rodney Ehrlich, Health Sciences UCT is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 South Africa License. Major contributors: Mohamed Jeebhay, Rodney Ehrlich, Jonny Myers, Leslie London, Sophie Kisting, Rajen Naidoo, Saloshni Naidoo. Source available from here. For any updates to the material, or more permissions beyond the scope of this license, please email healthoer@uct.ac.za or visit www.healthedu.uct.ac.za. Last updated Jan 2007.
Disclaimer note: Some resources and descriptions may be out-dated. For suggested updates and feedback, please contact healthoer@uct.ac.za.