CLASSES OF CHEMICALS

Toxic Chemicals

Reactive Chemicals

Flammables

Corrosives

Misc. (Cryogens & Compressed Gases)

Radioactive Materials

STRATEGY FOR HAZARD CONTROL

Hazard Recognition

Hazard Evaluation

Hazard Control

(article by Zwaard et. al.)

TOXIC CHEMICALS

1. DEFINITION

Chemicals, if taken internally, disrupt or interfere with normal metabolism and are thus harmful to human body.

Many classes of chemicals

2. MODES OF ENTRY INTO BODY

Inhalation –

Skin Absorption-

Ingestion-

Injection-

3. TYPES OF TOXIC EFFECTS

Acute Toxicity –

Causes immediate damage as result of single or short term exposure. Health problem readily apparent.

Chronic Toxicity –

Causes damage after repeated or long term exposure. Becomes evident after a long latency period.

4. CLASSES OF TOXINS

Organ specific-

Carcinogens –

Mutagens-

Teratogens-

Allergens -

5. FACTORS AFFECT TOXICITY

Quantity of substance-

Length of exposure-

Rate absorption into bloodstream-

Physical / chemical properties of toxin-

Nature of biological system-

6. MEASUREMENT OF TOXICITY

Exposure By Inhalation

LC50 – Median Lethal Conc.

ppm or g/m3 air

Exposure By Other Routes

LD50 – Median Lethal Dose

g toxin / kg body weight

Safe Exposure Levels

TLV – Threshold Limit Value

- mg toxin / m3 air or ppm

a. TWA-

b. STEL-

c. C-

PEL – Permissible Exposure Level

7. EXAMPLES OF TOXINS

Heavy Metals –

Asbestos-

Organic Solvents-

Herbicides / Pesticides-

Formaldehyde-

a. Properties

b. Uses

c. Toxicity

d. Chronology of exposure levels

Phenol-

a. Properties

b. Uses

c. Toxicity

d. Problem

J. Doe weighs 190 lbs. He accidentally swallowed solution containing 5 oz. phenol. What are likely effects on J. Doe? LD50 for phenol = 530mg / kg.

Mercury-

a. History

b. Toxicity

c. Problem

Mercury (Hg) vapor has a TLV of 0.1mg Hg / m3 air at 250C and 1 atm total pressure. 1). Determine the vapor pressure (in mm) of mercury under these conditions. 2). Compare value to equilibrium vapor pressure of Hg (at 250C and 1 atm) which = 2 x 10-3 mm.

8. PRECAUTIONARY MEASURES WHEN USING TOXINS

Proper ventilation

Make substitutes

Personal protective wear

Good hygiene practices

Avoid breakages / spills

9. EMERGENCY PROCEDURES

Safety shower / eye wash

**Emergency Procedure For Spills

(be familiar with handout)

Spill Kits For Mercury