Introduction To Toxicology 1

Halogenated Aliphatic Hydrocarbons They include?

i) chloroform ii) trichloroethylene iii) 1,1,1-trichloroethane (methyl chloroform) iv) carbon tetrachloride v) tetrachloroethylene (perchloroethylene)

Nitrogen Oxides Clinical Effects The signs and symptoms of acute exposure to NO2 include?

i) cough ii) mucoid or frothy sputum production iii) dyspnea, and iv) chest pain v) Irritation of the eyes and nose vi) Pulmonary edema may appear within 1-2 hours

Halogenated Aliphatic Hydrocarbons -What can they be used for?

i) industrial solvents, ii) degreasing agents, and iii) cleaning agents.

What is an Ecosystem?

Ecosystem formed by the interaction of a community of organisms with their physical environment

Ecotoxicology

Ecotoxicology is concerned with the toxic effects of chemical and physical agents on populations and communities of living organisms within defined ecosystems also It includes the transfer pathways of those agents and their interactions with the environment. Ecotoxicology is concerned with toxic effects on populations of living organisms or on ecosystems.

Routes of Exposure

The route of entry for chemicals into the body differs in different exposure situations. In the industrial setting, inhalation is the major route of entry. The transdermal route is also quite important, but oral ingestion is a relatively minor route.

The sources of the major air pollutants include

The sources of these chemicals include a. transportation b. industry c. generation of electric power d. space heating and e. refuse disposal

Treatment of Nitrogen Oxides poisoning

There is no specific treatment for acute intoxication by NO2 Therapeutic measures for the management of deep lung irritation and noncardiogenic pulmonary edema are employed. These measures include maintenance of gas exchange with adequate oxygenation and alveolar ventilation. Drug therapy may include: i) bronchodilators ii) sedatives and iii) antibiotics.

Ozone penetration in the lung depends on ?

Tidal volume Consequently, exercise can increase the amount of ozone reaching the distal lung.

Duration of Exposure

Toxic reactions may differ qualitatively depending on the duration of the exposure. a. Acute exposure: A single exposure occurring over 1 or 2 days—represents acute exposure. b. Chronic exposure Multiple exposures continuing over a longer period of time represent a chronic exposure.

Traditional toxicology

Traditional toxicology is concerned with toxic effects on individual organisms.

Environmental Toxicology -Definition -Environment Humans are considered a target species of particular interest, other species are of considerable importance as potential biologic targets.

Definition: Environmental toxicology deals with the potentially deleterious impact of chemicals, present as pollutants of the environment, on living organisms. Environment = all the surroundings of an individual organism, but particularly the air, soil, and water.

Occupational Toxicology

Definition: Occupational toxicology deals with the chemicals found in the workplace. The major emphasis of occupational toxicology is: a. To identify the agents of concern b. To define the conditions leading to their safe use c. To prevent absorption of harmful amounts. Identify, define, prevent

Clinical Effects & Treatment Ozone (O3 ) poisoning

CLINICAL EFFECT Ozone (O3 ) is an irritant of mucous membranes. i) Mild exposure produces upper respiratory tract irritation. ii) Severe exposure can cause deep lung irritation, with pulmonary edema when inhaled at sufficient concentrations. Ozone penetration in the lung depends on tidal volume; consequently, exercise can increase the amount of ozone reaching the distal lung. Management i) Depends on therapeutic measures utilized for deep lung irritation and noncardiogenic pulmonary edema (see Nitrogen Oxides, above)

AIR POLLUTANTS Five major substances account for about 98% of air pollution. They include?

Five major substances account for about 98% of air pollution: a. Carbon monoxide (52%) b. Sulphur oxides (14%) c. Hydrocarbons (14%) d. Nitrogen oxides (14%) and e. Particulate matter (4%).

Definition of toxicology

General: Toxicology is concerned with the hurtful/harmful effects of these chemical agents on all living systems. Biomedical: Toxicology is primarily concerned with adverse effects in humans resulting from exposure to drugs and other chemicals as well as the demonstration of safety or hazard associated with their use.

TOXICOLOGIC TERMS & DEFINITIONS Hazard

Hazard is the ability of a chemical agent to cause injury in a given situation or setting; the conditions of use and exposure are primary considerations. To assess hazard, one needs to have knowledge about both a. the inherent toxicity of the substance and b. the amounts to which individuals are liable to be exposed.

Carbon Monoxide

IUPAC NAME: Carbon Monoxide OTHER NAMES: Carbon(II) oxide CHARACTERISTICS i. colourless ii. tasteless iii. odourless iv. non-irritating gas v. a byproduct of incomplete combustion. MECHANISM OF ACTION i. Combination with oxygen ii. Role of carboxyhemoglobin i. Combination with oxygen Carbon monoxide(CO)combines reversibly with the oxygen-binding sites of hemoglobin and has an affinity for hemoglobin that is about 220 times that of oxygen. ii. Role of carboxyhemoglobin The product formed, carboxyhemoglobin, cannot transport oxygen it instead interferes with the dissociation of oxygen from the remaining oxyhemoglobin, thus reducing the transfer of oxygen to tissues. **The brain and the heart are the organs most affected. CLINICAL EFFECTS The principal signs of CO intoxication are those of hypoxia - (oxygen deficiency) and progress in the following sequence: i. psychomotor impairment ii. headache and tightness in the temporal area iii. confusion and loss of visual acuity iv. tachycardia, tachypnea, coma v. deep coma, convulsions, shock, and respiratory failure.

Nitrogen Oxides

IUPAC NAME: Nitrogen Oxides OTHER NAMES: CHARACTERISTICS i) A brownish irritant gas sometimes associated with fires. It is formed also from fresh silage; ii) exposure of farmers to NO2 in the confines of a silo can lead to silo-filler's disease. MECHANISM OF ACTION i) Nitrogen dioxide (NO2 ) is a deep lung irritant capable of producing pulmonary edema. Aliquots -Exposure to 25 ppm is irritating to some individuals; -50 ppm is moderately irritating to the eyes and nose. -Exposure for 1 hour to 50 ppm can cause pulmonary edema and perhaps subacute or chronic pulmonary lesions -100 ppm can cause pulmonary edema and death.

Sulphur Dioxide

IUPAC NAME: Sulphur Dioxide OTHER NAMES: Sulphur(IV)oxide CHARACTERISTICS Sulfur dioxide (SO2) is a i) Colourless ii) irritant gas iii) generated primarily by the combustion of sulfur containing fossil fuels. MECHANISM OF ACTION i) Formation of sulfurous acid On contact with moist membranes, SO2 forms sulfurous acid, which is responsible for its severe irritant effects on the eyes, mucous membranes, and skin. ii) Absorption in the upper respiratory tract It is estimated that approximately 90% of inhaled SO2 is absorbed in the upper respiratory tract, the site of its principal effect. CLINICAL EFFECTS The signs and symptoms of intoxication include : i) Irritation of the eyes, nose, and throat and ii) reflex bronchoconstriction. iii) Severe exposure cause delayed onset pulmonary edema . TREATMENT Treatment is not specific for SO2 but depends on therapeutic maneuvers utilized in the treatment of irritation of the respiratory tract.

Carbon Monoxide -Treatment

In cases of acute intoxication i) removal of the individual from the exposure source ii) maintenance of respiration is essential, followed by iii) administration of oxygen—the specific antagonist to CO—within the limits of oxygen toxicity. .....hyperbaric oxygen

MECHANISM OF ACTION of Halogenated Aliphatic Hydrocarbons CLINICAL EFFECTS of Halogenated Aliphatic Hydrocarbons

MECHANISM OF ACTION These substances are depressants of the central nervous system in humans, their relative potencies vary considerably; chloroform is the most potent and was widely used as an anesthetic agent. CLINICAL EFFECTS The halogenated hydrocarbons cause : i) central nervous system depression -Chronic exposure to tetrachloroethylene can cause impaired memory and peripheral neuropathy ii) liver injury iii) kidney injury, and iv) some degree of cardiotoxicity.

Ozone

Ozone (O3 ) is a i) Bluish irritant gas that occurs normally in the earth's atmosphere, where it is an important absorbent of ultraviolet light. In the workplace, it can occur around high-voltage electrical equipment and around ozone-producing devices used for air and water purification. It is also an important oxidant found in polluted urban air.

TOXICOLOGIC TERMS & DEFINITIONS Risk

Risk is defined as the expected frequency of the occurrence of an undesirable effect arising from exposure to a chemical or physical agent. Estimation of risk makes use of a. dose-response data and b. extrapolation from the observed relationships to the expected responses at doses occurring in actual exposure situations.

Classification of Toxicology

a. Occupational Toxicology b. Environmental Toxicology c. Ecotoxicology

Atmospheric pollutants gain entry by ---------- Pollutants of water and soil, --------- is the principal route of exposure for humans.

a. inhalation b. oral ingestion

exposure of farmers to NO2 in the confines of a silo can lead to -------

silo-filler's disease.

Chemicals in the occupational setting vs chemicals found in the environment wrt to duration of exposure

✓ In the occupational setting, both acute (eg, accidental discharge) and chronic (eg, repetitive handling of a chemical) exposures may occur, whereas ✓ with chemicals found in the environment (eg, pollutants in ground water), chronic exposure is more likely.

TREATMENT of Halogenated Aliphatic Hydrocarbons intoxication

✓ There is no specific treatment for acute intoxication resulting from exposure to halogenated hydrocarbons. ✓ Management depends on the organ system involved