Chemical
exposures can trigger asthma. You can actually develop an allergy to a chemical
when your immune system recognizes it specifically as a foreign substance.
For example, automobile spray painters can develop
allergies to chemicals called isocyanates. Even in lower concentrations, many
chemicals are irritants and will trigger symptoms in asthmatics that have
twitchy hyperresponsive airways.
Exposure to industrial and household cleaning products is
linked with asthma: disinfectants, bleach, air fresheners, furniture polish,
etc.
In toxicology, asthma research is determining chemicals that have the potential of causing asthma in occupations that produce the chemical or in consumers who use the chemical product.
Screening methods and setting limits of exposure to these
chemicals is a continuing challenge to protect both workers and consumers from
developing asthma.
TOXICOLOGY
- is the study of the nature and
action of poisons; the adverse health effects of chemical materials.
Toxicity is the ability of a chemical to
produce injury once it reaches a susceptible site in or on the body.
Descriptions of toxicity (e.g. low, moderate, severe, etc.) depend on dose
needed to cause an effect or the severity of that effect.
Dose-Response Relationships: “The
Dose Makes the Poison”
A
chemical thought of as “harmless” may produce a toxic response if added to a
biological system in a sufficient amount or dose. The potency of a chemical is
ultimately defined by the relationship between the dose (the amount) of the
chemical and the response that is produced in a biological system.
Routes of Entry into the Body
Absorption
through the:
• respiratory
tract via inhalation
Types of Effects
Acute poisoning is characterized by rapid
absorption of the substance and the exposure is sudden and severe. Normally, a
single large exposure is involved. Examples: carbon monoxide or cyanide
poisoning.
Chronic poisoning is prolonged or repeated low level
exposures of a duration measured in days, months or years. Signs and symptoms
may not be immediately apparent. Examples: lead, mercury, asbestos, silica.
Local refers to the site of action of an
agent and means the action takes place at the point or area of contact. The
site may be skin, mucous membranes, the respiratory tract, gastrointestinal
system, eyes, etc. Absorption does not necessarily occur. Examples: strong
acids or alkalis and chemical warfare gases.
Systemic refers to a site of action other
than the point of contact and presupposes absorption has taken place.For
example, an inhaled material may act on the liver. Other examples: arsenic
affects the blood, nervous system, liver, kidneys and skin; benzene affects
bone marrow.
Cumulative poisons are characterized by materials that
tend to build up in the body as a result of numerous chronic exposures. The
effects are not seen until a critical body burden is reached. Example: heavy
metals.
Substance in Combination: When two or more hazardous
materials are present at the same time, the resulting effect can be greater
than the effect predicted based on the individual substances. This is called a synergistic
or potentiating effect. Example: exposure to alcohol and chlorinated solvents.
Other Factors Affecting Toxicity
- Rate of entry and route of exposure
- Age can affect the capacity to
repair tissue damage.
- Previous exposure can lead to
tolerance, increased sensitivity or make no difference.
- Host factors, including genetic
predisposition and the gender of the exposed individual.
- State of health, physical condition
and life style can affect the toxic response. Preexisting disease can result in
increased sensitivity.
- Environmental factors such as
temperature, humidity and atmospheric pressure.
Classification
of Toxic Materials
Simple and Chemical Asphyxiants
Simple asphyxiants
are inert gases that displace oxygen while chemical asphyxiants render the body
incapable of utilizing an adequate oxygen supply, e.g., carbon monoxide
prevents hemoglobin from binding oxygen.
Hepatotoxic Agents
Hepatotoxic agents
that can cause damage to the liver.
Nephrotoxic Agents
Nephrotoxic agents
causes damage to the kidneys. Signs and symptoms: edema; proteinuria
Neurotoxic Agents
Neurotoxic agent
damages the nervous system. Signs and symptoms: narcosis; behavioral changes; decreased
muscle coordination.
Hematopoietic Agents
Some toxic agents
act on the blood. The blood cells can be affected or
bone marrow can be
damaged. Signs and symptoms: cyanosis; loss of consciousness.
Pulmonary Agents
Fibrotic changes
can be caused by free silica and asbestos. Other dusts can cause a restrictive
disease called pneumoconiosis. Signs and symptoms: cough; tightness in chest,
shortness of breath.
Carcinogens
A carcinogen
describes an agent that can initiate or speed the development of malignant or
potentially
malignant tumors.
Reproductive Toxins
Reproductive
toxins affect the reproductive system (mutations, sterility and teratogenesis).
Mutagens
A mutagen is a
chemical which causes alterations in the nucleic acids of exposed cells or
organisms.
Teratogens
A teratogen
(embryotoxic, fetotoxic agent) is an agent which interferes with embryonic
development without damage to the mother or lethal effect on the
fetus.
For further reading, please visit http://www.eoearth.org/topics/view/49498/
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