environmental health

Occupational Chemical Hazards

Dr Faris Al Lami
MB,ChB MSc PhD FFPH

Objectives

Identify the main chemicals imposing occupational hazards, and routes of exposure
Describe occupational dermatitis
Describe main types of occupational cancers
Define methods of prevention and control of chemical hazards in occupational setting

3
Chemicals
There are 5-7 million chemicals known in the world.

At least 400 million tonnes of chemicals are produced worldwide each year (including agricultural chemicals, food additives, fuels for power production, chemical consumer products, etc.)

For the majority of chemicals used in the workplace, little or nothing is known about their possible immediate or long-term health effects.


OCCUPATIONAL DISEASES
Chemical Agents causing Occupational Diseases
• Gases -
• * Simple asphyxiants : N2, CH4, CO2
• * Chemical asphyxiants : CO, H2S, HCN
• * Irritant gases : Ammonia, SO2, Cl2,
• * Systemic poison : CS2

Dusts (Pneumoconiosis)

Inorganic dusts:
Coal dust - Anthracosis
Silica - Silicosis
Asbestos - Asbestosis.
Iron - Siderosis

Organic dusts :

Cane fiber - Bagassosis
Cotton dust – Byssinosis.
Hay or grain dust – Farmer’s lung

Metals - Lead, Mercury, Chromium, Manganese arsenic, cadmium, zinc, beryllium, tin, silver, etc)
Chemicals - Acids, Alkalies
Solvents - Benzene, Trichloroethylene, Toluene, Zylene, Phenol, Nitrate, Napthalene, Isocyanates, Carbon tetrachloride, Carbon disulphide, Vinyl chloride monomer, etc


Routes of Exposure
Inhalation
airborne contaminants
Absorption
through the skin or eyes
Ingestion
eating
drinking
Injection
high-pressure sprays into skin or eyes

8
Gases

Sulphur oxides,

Nitrogen oxides,
Chlorine,
Ammonia

Some toxic gases are corrosive and irritating to the respiratory system.

Hydrogen cyanide


Some gases can pass through the skin
Carbon monoxide

Some gases may enter the blood circulation.

Carbon-Dioxide
• Has no odor
• Heavier than air
• TLV exposure limit is 5,000 ppm
• Can cause death by asphyxiation

Ammonia

• Odor detection limit 1-5 ppm
• Irritating 50 ppm (eyes), 100 ppm (respiratory tract)
TLV 25 ppm
Lethal 10,000 ppm
Irritant in nature

Hydrogen Sulfide (H2S)

Flammable, colorless gas that is toxic at extremely low concentrations
Other names include sour gas, stink damp
Smells like rotten eggs even at low concentrations
Causes a worker to quickly loose the sense of smell
Heavier than air and can accumulate in low-lying areas
In exposure of >500 ppm can lead to unconsciousness, dizziness, death


Solvents
Most industrial solvents are liquid organic chemicals

Many of them evaporate rapidly at ambient temperatures

They are often flammable and may ignite by heat from smoking, welding or static electricity.

Example of very dangerous solvents:Benzene, carbon tetrachloride, carbon disulphide.

13
Metals
Metals can enter the body in the form of dust and fumes (in grinding or welding) or even through the skin.

Lead is used in various industries: battery, glass and mining industries, cable manufacturing, foundries and in printing works.
It can cause serious damage to the nervous system, kidneys, a rise in blood pressure.

Mercury is present in many pesticides.

Mercury vapours are inhaled, as this liquid metal evaporates readily at room temperatures.
Mercury poisoning has serious effects on the nervous system.

Nickel is present with other metals in various alloys. Nickel and its compounds are known to be sensitizers. Some compounds of nickel can cause cancer.
Chromium compounds, are widely used in industry. Some compounds can cause allergy and even lung cancer. Chromium compounds may cause birth defects.
Arsenic compounds are used in pesticides, insecticides and in some colouring materials. Arsenic and its compounds can cause cancer.


Pesticides
Pesticides are used in industry, for example, to impregnate wood, and in agriculture to control insects, weed, fungi, and rats.
The most commonly reported effects is Dermatitis
Some individuals tend to cough,wheeze, or sneeze
In advanced poisoning cases, the individual may experience changes in heart rate, difficulty breathing, convulsions, and coma, which could lead to death.
Inorganic mercury compounds, camphechlor, chlordane, dieldrin, DDT, HCH (lindane), heptachlor, hexachlorobenzene, and nitrofen were banned in some countrie

Occupational Dermatitis

Endogenous (constitutional)

Exogenous (contact)
Irritant (acute/chronic)
Allergic (immediate/delayed)

Occupational Dermatitis

Allergic
Latency
Lag period
Eyelid swelling
Papules and vesicles
Exposure to a known sensitizer


Irritant
usually involves the hands
Scaling and redness
Papules and vesicles are unusual
Exposure to a known irritant

Some of the chemicals that cause contact dermatitis are:

Formaldehyde
Nickel compounds
Epoxy resins and catalysts used in the plastics industry
Germicidal agents used in soap and other cleaners
Chromates

History

Duration
Site
Work history
Exposure to known allergens/irritants
Improvement away from work

Management

Avoid exposure
Allergen/irritant replacement
Skin protection
Change job
Drug treatment


Occupational Cancer
Target Organ
Lung

Nasal sinuses

Urothelial tract

Liver (angiosarcoma)

Carcinogen
Asbestos, As, Be, Cd, Cr, Ni, Fe
Ni
Rubber, Dyes, Al, Tar

Vinyl Chlorides

Steps to Protect Workers
Anticipate potential hazards
Recognize potential hazards
Evaluate exposure and risk
Control exposure and risk
Eliminate
Substitute
Enclose/separate
PPE/vaccinate


Controls
Engineering controls (remove hazard)
process change, chemical substitution
ventilation, shielding, guarding
requires little or no worker action

Examples:

Self-capping syringe needles,
Ventilation systems such as a fume hood
Sound-dampening materials to reduce noise levels
Safety interlocks
Radiation shielding

Controls

Administrative (or work practice) controls (manage exposure)
Changes in work procedures such as: written safety policies, rules, supervision, schedules, training worker, rotation
controlled access areas
requires worker action
The goal is reducing the duration, frequency, and severity of exposure to hazardous chemicals

Controls

Personal protective equipment (PPE)
respirators, gloves, clothing
requires individual worker action
last line of defense

MEDICAL MEASURES

Pre-employment medical check up
Periodic medical examination
Health promotion
Health education
Specific protection
Assessment of risk by supervision of working environment

Pre-employment Medical Examination

To determine the physical and emotional capacity of the individual to perform the job.
To provide baseline health data for epidemiological and legal purposes.
To counsel the person for correction of diseases / habits which may harm later.
Assessment of pre-existing toxicity / impairment due to past exposure, if any.


Pre-placement Medical Examination

Periodic Medical Examination

Evaluation of general health status.
Earliest detection and prevention of work related disorders.
Early detection, control and prevention of any health disorder which may affect the ability to perform the job.
To detect deviation in health status from baseline data.
Detection of infectious / communicable diseases which may affect others.

Qs?