Toxic and Hazardous Chemicals
The toxicity of a substance is its ability to cause harmful effects. These effects can strike a single cell, a group of cells, an organ system, or the entire body. A toxic effect may be visible damage or a decrease in performance or function measurable only by a test. All chemicals can cause harm. When only a very large amount of the chemical can cause damage, the chemical is considered to be practically non-toxic. When a tiny amount is harmful, the chemical is considered to be highly toxic.
The toxicity of a substance depends on three factors: its chemical structure, the extent to which the substance is absorbed by the body, and the body’s ability to detoxify the substance (change it into less toxic substances) and eliminate it from the body.
No. The toxicity of a substance is the potential of that substance to cause harm and is only one factor in determining whether a hazard exists. The hazard of a chemical is the practical likelihood that the chemical will cause harm. A chemical is determined to be a hazard depending on the following factors:
- Toxicity: How much of the substance is required to cause harm,
- Route of exposure: How the substance enters your body,
- Dose: How much enters your body,
- Duration: The length of time you are exposed,
- Reaction and interaction: Other substances you are exposed to at the same time, and,
- Sensitivity: How your body reacts to the substance compared to other people.
Some chemicals are hazardous because of the risk of fire or explosion. These are important dangers but are considered to be safe rather than toxic hazards. The factors of a toxic hazard are more fully explained below.
Why Are Some Chemicals More Harmful Than Others?
The most important factor in toxicity is the chemical structure of a substance (i.e., what it is made of), what atoms and molecules it contains, and how they are arranged. Substances with similar structures often cause similar health problems. However, slight differences in chemical
structure can lead to large differences in the type of health effect produced. For example, silica in one form (amorphous) has little effect on health and is allowed to be present in the workplace at relatively high levels. After it is heated, however, it turns into another form of silica (crystalline) that causes serious lung damage at levels 200 times lower than amorphous silica.