750 Introduction to Industrial Hygiene

Chemical Hazards

Introduction

Harmful chemical compounds in the form of solids, liquids, gases, mists, dusts, fumes, and vapors exert toxic effects by inhalation (breathing), absorption (through direct contact with the skin), or ingestion (eating or drinking).

Airborne chemical hazards exist as concentrations of mists, vapors, gases, fumes, or solids. Some are toxic through inhalation and some of them irritate the skin on contact. Others may be toxic by absorption through the skin or through ingestion, and some are corrosive to living tissue.

Degree of Risk

The degree of worker risk from exposure to a hazardous substance depends on four main factors: toxicity, dose, frequency, and duration.

• Toxicity – This refers to how harmful a substance is by nature. Some substances can cause serious health effects even in small amounts. For example, asbestos fibers can lead to lung disease and cancer when inhaled, while common soil dust is usually less harmful unless large amounts are inhaled over time. Another example is carbon monoxide, which is highly toxic because it can quickly reduce oxygen levels in the blood.
• Dose – This is the amount of the substance a worker takes into the body during exposure. A higher dose usually leads to a higher risk. For example, a worker who inhales a large amount of chemical fumes in a short time may become sick quickly, while a smaller amount may cause little or no immediate effect. A painter working in a poorly ventilated area may receive a higher dose of solvent vapors compared to one working outdoors.
• Frequency – This describes how often a worker is exposed to the substance. Repeated exposure can increase risk, even if each exposure is small. For example, a worker who handles cleaning chemicals every day faces a higher risk than a worker who uses the same chemicals once a month. Over time, repeated contact can lead to skin irritation, breathing problems, or other health issues.
• Duration – This refers to how long each exposure lasts. Longer exposure times can increase the risk of harm. For example, a worker exposed to loud noise or airborne contaminants for an entire shift faces greater risk than a worker exposed for only a few minutes. Long-term exposure, such as working with hazardous materials over several years, can lead to chronic health conditions.

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