Safety and Health, Essay Example

In Chapter 24, the focus is on chemical compounds.  The interest in chemicals by the general public has become greatly increased recently due to chemical catastrophes in India, Michigan, New York, and other locations.  In India in 1988, methyl isocyanate gas leaked from a chemical plant and settled over a 15 square mile area.  The chemical killed 2,500 people and injured 20,000 others.  Because of events like this, the public has become rightly concerned with chemicals.  There are a multitude of chemical compounds, greater than 3,000,000 registered compounds, of which approximately 60,000 have economic value in the marketplace.  Another estimated 700-1000 compounds enter the marketplace each year.  According to NIOSH, 5000 chemicals have some inherent hazards.  However, only 500 chemical compounds have published exposure standards.  So, many chemicals are lacking published hazards.

The three main types of hazards for chemicals are: 1. health effects , 2. fires and explosions, and 3. reactivity with other materials.  Chapter 24 mainly focuses on the different health effects of chemical compounds.  It is important to note that the hazards are interrelated.  That is, a fire can cause a chemical to become less stable and more reactive.  As the chemical becomes more reactive it can cause more serious health effects, so it becomes very important to understand how to properly address each of the hazards without causing greater hazards.

Since the focus of this chapter is health effects, this summary will mainly address those concerns.  There are three main entries into the body for chemicals, inhalation, ingestion, and absorption.  To understand the health effects of inhalation, one must understand the two forms of airborne contaminants: particulates and gases or vapors.  Particulates are classified by their size and chemical makeup and include dusts, fumes, smoke, aerosols, and mists.  The shape of the particulate is also important as some are spherical while others are long and fibrous.  Dusts are made of fine particulate matter created from processes that break matter into smaller pieces.  Fumes are fine solids often formed from the condensation of vapors.  Smoke is carbon or soot particles that result from incomplete combustion of carbonaceous materials.  Aerosols are solid or liquid particulates that are dispersed in the air.  Mists are liquid droplets that are suspended in or falling through air.  Gases are a different state of matter from solids or liquids.  Lastly, vapors are the gaseous phase of a substance that is a liquid at normal temperature and pressure.

When chemicals enter the body, they often affect particular organs of the body.  The effects on the organs can cause physical change, such as headache and nausea, and behavioral change, such as hallucinations and confusion.  Three factors determine the damage that the chemical will cause.  One is the type and form of the substance, two is the type and rate of exposure, and three is what happens to the substance in the body.  The time of exposure affects the latency period.  Some chemicals cause immediate effects while others may not have effects for years, as is the case with carcinogens.  Time also determines if an exposure is acute or chronic.  An acute exposure is one that causes damage in a single short exposure.  A chronic exposure is one that causes damage over a long period of multiple exposures.  Additionally, health effects can be local or systemic.  A local effect is one that causes injury to eyes, skin, or the respiratory tract after one or more exposures.  A systemic effect occurs when a substance enters the body and disrupts organs or other biological functions.  Interestingly, chemicals known as asphyxiants do not directly affect the body.  Instead, they displace oxygen which then causes damage to the organs and tissues of the body.  Some of the most serious health effects from chemicals are carcinogens, mutagens, and teratogens.  A substance that falls into one of these three categories causes damage to the DNA of a person resulting in a wide-range of effects for a long period of time.

Interestingly, not every person reacts the same to a chemical.  Some people have allergies to chemicals that cause increased responses.  Others become desensitized through exposure and do not show health effects until they are placed in repeated exposures.

So, what methods are used to assess the toxic properties of these chemicals, given that they have sometimes serious and wide-ranging effects?  The first method is through human experimentation.  However, it is unethical to test chemicals on humans for toxicity.  So, human experimentation is no longer used to test chemicals if the chemical is suspected to be toxic.  Another more useful method of assessing toxicity is through human experience.  While we do not allow humans to be exposed on purpose, sometimes they are exposed through accident.  By studying the outcomes of these accidents, the effects of the chemicals involved can be gauged.  Most toxicity data comes from the use of animal experimentation.  When chemicals are tested on animals that are similar in physiology to humans, much can be learned about their effects.  There are some drawbacks to this procedure.  For instance, a chemical with a long latency time must be tested at higher doses than a human would normally encounter in order to speed up the effects.  This process means that the animal experiments are useful for the study of toxicity in humans but not completely reliable.  Lastly, chemicals can be tested on microorganisms in order to more quickly get results.  These tests are generally short-term as microorganisms have such a short life.  The most common of these tests is the Ames test.

Chemicals are some of man’s greatest inventions, but they have the potential for great harm.  One must understand how the chemical works and how it can be toxic to a human in order to handle it safely.