Toxic Gases: Classification and Routes of Exposure

Lower Respiratory Tract

• The main function of the lower respiratory tract is to facilitate gas exchange.

Toxic Gases

• Chemicals that induce cellular hypoxia or anoxia are classified as chemical asphyxiants.
• Carbon monoxide (CO) is an odorless, colorless, and nonirritating gas, labeled as the silent killer.

Routes of Exposure

• Toxic gases can enter the body through inhalation, ingestion, or skin absorption.

Respiratory System

• The lower respiratory system consists of the trachea, bronchi, bronchioles, and lungs.

Chemical Asphyxiants

• Chemical asphyxiants frequently interfere with cellular respiration to produce toxicity.

Blood CO Levels

• The normal range for adult blood CO levels is not specified in the text.

Tobacco Smoke

• Tobacco smoke is a major source of CO.

CO Toxicity

• The mechanism of CO toxicity involves the binding of CO to ferrous ion (Fe+2) in hemoglobin (Hb).
• CO binds to Hb with an estimated strength 210-240 times greater than molecular O2.

COHb Formula

• The formula used to estimate the degree of binding of CO to Hb is not specified in the text.

COHb Levels

• COHb levels above 10% are considered potentially harmful in nonsmokers, and above 15% in smokers.

COHb Half-Life

• The approximate half-life of COHb is not specified in the text.

Acute CO Exposure

• Symptoms of acute, mild exposure to CO include headaches, dizziness, and nausea.

Metabolism

• Methanol is metabolized by hepatic mixed function oxidases to CO and CO2.

CO Sources

• Cigarette smoke, automobile exhaust, and faulty furnaces are sources of CO; methane is NOT a source of CO.