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 CHEMICAL HAZARDS

Chemical  are hazards associated with transportation, storage and handling of chemicals.

 Such hazards include:

1. Corrosive, reactive, toxic,  harmful or irritating chemicals
2. Fire –caused by flammable chemicals.
3. Cancer due to radioactive  substances and mutage

I. Corrosive chemicals

Corrosives are materials, such as acids and bases (caustics, alkalis) which can damage body tissues because of splashing, inhalation or ingestion.

 They may also corrode metals while releasing flammable hydrogen gas.

They may damage some plastics.

Some corrosives, such as Sulphuric, Nitric and Perchloric acids are also oxidizers; thus, they are incompatible with flammable or combustible material.

They may release toxic or explosive products when reacted with other chemicals.

They may liberate heat when mixed with water.

Precautions for handling corrosive materials

1. Wear appropriate skin and eye protection
2. Use in the weakest concentration possible
3. Handle in a chemical fume hood.
4. Use secondary containers when transporting and storing corrosives
5. Always dilute by adding acids to water
6. Dilute and mix slowly
7. Store acids separately from gases

a. Reactive chemicals

Reactive chemicals are those chemicals that may

1. Be sensitive to jarring, compression, heat or light
2. React dangerously with water or air
3. Burn, explode or yield flammable or toxic gases when mixed with incompatible materials.
4. Vigorously decompose, polymerize or condense
5. Be toxic, corrosive, oxidizing or flammable
6. NB; some chemicals may not be dangerous when purchased but may develop hazardous properties over time (e.g. diethyl ether and solutions of picric acid).

Precautions for Reactive Chemicals

Follow these precautions when working with dangerously reactive chemicals:

1. Understand the hazards associated with these chemicals and use them under conditions which keep them stable
2. Store and handle away from incompatible chemicals
3. Keep water-reactive chemicals away from potential contact with water, such as plumbing, fire sprinkler heads and water baths
4. Handle in a chemical fume hood
5. Wear the appropriate skin and eye protection
6. Work with small quantities
7. Use up or dispose of these chemicals before they attain their expiry date

    c. Nerve poisons

Nerve poisons are those that when they are absorbed into the body   , they upset the nervous system e.g. morphine, opium etc.

Nerve poisons are divided into two i.e.  

1. Sedatives – they cause the nervous system to relax
2. Stimulants – cause the nervous   system to be excited

d. Irritating chemicals

Irritating chemicals can cause inflammations and irritation of skin, mucus membranes and respiratory tract following immediate or prolonged exposure e.g. ammonia, potassium dichromate etc

All chemicals in the laboratory should be regarded as poisonous including distilled water.

a. Carcinogens, Mutagens. Allergens

Carcinogens

Carcinogens are chemicals that have ability to induce cancer. Carcinogenic effects takes long before its symptoms appear unlike toxic chemicals.

Mutagens

Mutagens are chemicals, which produce mutation of the germ cells leading to generally induced malformation, spontaneous abortion or death of the offspring upon exposure.

Allergens- Allergens are chemicals, which causes allergy or hypersensitivity reaction when they are exposed to the skin causing dermatitis, when inhaled they cause asthma.

General safe use and storage of toxic substance

1. Highly toxic, irritating and harmful chemicals should be stored under lock and key.
2. Only authorized persons should handle toxic chemicals.
3. Highly toxic chemicals should always be handled with care and hands should be washed after handling them also wear protective clothing is when handling them.
4. Fuming chemicals should be handled in a fume chamber.
5. Never taste or mouth pipette any chemical in the laboratory or use any laboratory ware for food as utensils.
6. Avoid using  carcinogenic substances in the laboratory instead seek  alternative safer substitute for them
7. Young children and expectant mothers should not come closer to carcinogenic substances.
8. Corrosive chemicals should be stored at lower level shelves.
9. Never store NaOH and KOH in a ground glass stopper.
10. Always pour corrosive chemical at below eye level, slowly and with great care to avoid splashing.
11. When opening a corrosive chemical, place a cloth over the neck of the bottle.
12. Exercise great care when diluting  or dissolving corrosive chemicals e.g. Na,K,
13. Never add water to an acid but add acid to water slowly by the edge of the bottle.

b. Oxidizing chemicals

These are substances that evolve  O₂ when they come in contact with other substances  and may cause them to burn  strongly or become explosive  in presence of heat e.g. peroxides , dichromate’s , KmnO₄, chlorates etc.

Oxidizing chemicals can increase the speed and intensity of a fire by adding to the oxygen supply, causing materials that would normally not burn to ignite and burn rapidly.  Oxidizers can also:

1. React with other chemicals, resulting in release of toxic gases.
2. Decompose and liberate toxic gases when heated
3. Burn or irritate skin, eyes, breathing passages and other tissue

Precautions using and storing oxidizers

1.  Keep away from flammable and combustible   materials.
2. Keep containers tightly closed unless otherwise indicated by the supplier.
3. Mix and dilute according to the supplier’s instructions
4. To prevent release of corrosive dusts, purchase in liquid instead of dry form.
5. Reduce reactivity of solutions by diluting with water
6. Wear appropriate skin and eye protection
7. Ensure that oxidizers are compatible with other oxidizers in the same storage area

c. Flammable and combustible chemicals

Flammable and combustible substances are substances, which readily catches fire, and burns.  These chemicals have low flash point i.e. low temperatures at which the vapor above the liquid can be ignited in air .They therefore have high risk of catching fire

Classification of flammable chemicals

Extremely flammable chemicals

These are liquids with a flash point below 0^oc and a boiling point of 35^oc or below e.g. acetone and diethyl ether

Highly flammable chemicals

They are liquids with flash points below 21^oc or solids which readily ignite after a brief contact with a flame or which evolve highly inflammable gases when in contact with water or moist air e.g. absolute ethanol and methanol

 Flammable chemicals

 They are liquids with flash points of between 21^oc and 55^oc e.g. glacial acetic acids, xylene or acetic hydride.

Safety storage and use of flammable chemicals

1. Keep only small quantities of flammable chemicals on laboratory benches and shelves.
2. Store stock supplies particularly those that are highly flammable in a closed steel or thick plywood box at ground level shelves preferably in a cool and well ventilate outside locked store.
3. Do not store oxidizing and reducing chemicals together.
4. The storeroom should have adequate, suitable and well-maintained fire extinguisher. The lab should also be well ventilated.
5. Avoid naked fires near the store or when opening the container containing flammable chemicals
6. Flammable chemical containers should be always tightly sealed to discourage escape of vapor.
7. Place a NO SMOKING label on the door to discourage smoking around the flammable store
8. Use tray to hold the container to prevent the liquid from spilling on the floor in case of spillage.
9. Use water bath to heat flammable chemicals.

d. Poisonous chemicals

A poisonous chemical is any substance which when taken into the body in insufficient quantities is capable of injuring or causing death to the casualty.

The term “toxic” relates to poisonous or deadly effects on the body by inhalation (breathing), ingestion (eating), or absorption, or by direct contact with a chemical                                                                                    

 A toxicant is any chemical that can injure or kill humans, animals, or plants.

The term “toxicant” is used when talking about toxic substances that are produced by or are a by-product of human-made activities

The word “toxicity” describes the degree to which a substance is poisonous or can cause injury.

The toxicity depends on a variety of factors: dose, duration and route of exposure, shape and structure of the chemical itself, and individual human factors.

Routes of Poison Entry Into Body

Toxins can gain entry into the body by:

1. Inhalationof gases, vapors and particulate material (e.g. mists, dusts, smoke, and fumes).
2. Absorptionthrough skin of liquids, solids, gases and vapors.
3. Ingestion of chemicalsdirectly or indirectly via contaminated foods and beverages and contact between mouth and contaminated hands (nail-biting, smoking).
4. Injection of chemicalsthrough needles and other contaminated laboratory sharps

EFFECTS OF TOXIC SUBSTANCES.

Poisons cause undesirable effects to living organisms. They can cause one or more toxic effects, which can also be immediate (acute) or long term (chronic).  Toxic effects of toxic substances may be classified as follows

(i) Local toxic effects

 Local toxicity effects are those that occur at the site of first contact between the biological system and the toxicant e.g. on skin,mouth, eyes and respiratory drugs.

(ii) Systemic effects

These effects always occur away from the site of body contact with the poison.  The poisons are absorbed and distributed away to some other sensitive sites e.g. in the central nervous system (neurotoxin), the liver (hepatoxin), kidney (renotoxin) and other hemopoetic tissues.

(iii) Selective toxicity

Refers to its ability to injure one   tissue, organ or cell without harming another   one even if the two organs, cells or tissues may be in intimate contact with each other.

(iv) Mutagenic effects

 A mutagen is a substance that cause damage to the genetic make-up or DNA of an organism. Exposure to chemical mutagens increases the likelihood of DNA damage and these can lead to hereditary

(v) Carcinogenic effects

 Carcinogenic substances are those substances that have the ability to induce cancer   or tumors to living organisms. Most but not all carcinogens act directly on the DNA.

 (vi)Teratogenic effects

Erotogenic effects involve the production of gross structural deformation or malformation during fetal development. These developmental abnormalities include body deformities or organ failure in newborns. These hazards normally arise during early periods of pregnancy i.e. when the embryo begins to form

(vii) Reproduction effects

These effects are caused during the time when female and the male reproductive systems processes such as ovulation and sperm production, implantation of the fertilized egg etc.