Chemistry Module 4
• Based on the nature of the work, safety hazards are due to material handling, machines,
energy, work practices, and confined spaces.
• Material handling hazards These can lead to muscle strains due to lifting and carrying
materials. The use of devices such as forklifts, cranes, etc. exposes the worker to
accidental contact with the moving equipment.
• Machine hazards: Rotating shafts, moving belts, presses, etc. can cause very serious
• Energy hazards All energy sources such as electricity, steam, hydraulic pressure, etc. can
lead to serious injury.
• Work practice hazards : Failure to follow safe operating procedures may lead to serious
• Confined space hazards: In such spaces (for example, silos, storage tanks, pipelines etc.)
hazards arise due to difficulty of entry and exit, buildup of hazardous materials and
• The extent of occupational health hazards varies with the type of activity. However, such
hazards may have the potential to cause severe discomfort, illness, and lack of efficiency
among workers. Based on the nature of the causative agent (or factor), occupational
health hazards can be classified as physical, chemical, biological and ergonomic.
• Physical hazard : due to the presence of physical agents such as pressure and temperature
extremes, excessive noise and vibration, and exposure to radiation.
• Chemical hazards: due to the presence of chemical agents such as dust, fume, gas, mist,
smoke and vapor.
• Biological hazards due to the presence of biological agents such as bacteria, moulds and
• Ergonomic hazards: due to ergonomic stresses such as fatigue and repetitious work.
Physical and Chemical
• Causative agent: classified as hazardous in certain circumstances such as high
concentration or intensity and a prolonged exposure
Workers have the right to:
• Work in a safe and healthy environment 2
• Know the processes and substances they are working with
• Know potential hazards from these processes and substances
• In order to recognize and assess the potential impact of occupational hazards, walk
through surveys are performed. Such surveys generally include a study of the following
parameters in terms of their impact on the surrounding environment and thus the workers.
• Processes, operations and related activiti : generally various emissions are evaluated
because the emission of any physical, chemical or biological agents has the potential to
be a health hazard.
• Equipment: generally assessed in terms of mechanical and electrical safety and the
potential to create excessive noise and vibration.
• Properties of substances used and produced: an evaluation of raw materials and finished
products in terms of their physical, chemical and toxic properties and effects.
• Control measures: all engineering controls in place for proper materials handling, storage,
etc. are evaluated. Also considered are the ventilation system and the availability of
personal protective equipment.
• Although we are constantly exposed to such agents, their intensity and duration of
exposure may be more significant in the workplace. Such agents may cause immediate or
cumulative adverse health effects.
• Commonly encountered physical conditions with a potential to cause adverse health
effects include: pressure and temperature extremes, excessive noise and vibration and
• The action of physical agents consists of transfer of residual energy through the
surrounding air or the equipment the worker is in contact with. Except for radiation, our
senses can detect all other physical agents.
• Our bodies are conditioned to work at normal atmospheric pressure. Any extreme can be
detrimental to one's health. Two types of abnormal pressurerelated conditions are
hyperbaric and hypobaric.
• Hyperbaric a pressure higher than normal atmospheric pressure. Mining and underwater
workers may be exposed to hyperbaric conditions.
• Hypobaric : a pressure lower than atmospheric pressure. Hypobaric conditions are
encountered by those working at high elevations such as ski instructors and airline pilots. 3
• The biochemical processes in one’s body take place within a very narrow temperature
range and hence the regulation of body temperature is an important function. Temperature
extremes affect the working efficiency as well as the health of a worker.
• Hot or cold depends on various factors
• It is important to realize that apart from the surrounding temperature, sensation of hot or
cold depends on some other factors such as: air movement, hot or cold objects in the
vicinity and relative humidity
• The terms heat stress and cold stress refer to excessive exposure to very hot or very cold
work environments. Both such conditions may interfere with worker’s performance and
may even be fatal.
• Some of the adverse effects in very hot work environments (depending upon the
individual worker and the heat intensity) include:
• Heat exhaustion
• Heat stroke
• Heatrelated problems may arise for:
• Outdoor workers (working in construction)
• Industrial workers (working near furnaces)
• In very cold work environments (depending upon the individual worker and intensity of
cold), the adverse effects include:
• Workers at risk include:
• Outdoor workers (divers)
• Meat packers and handlers (working in refrigerated warehouses)
• Noise is a form of irregular vibration. 4
• It may be conducted through gases (or vapors), liquids, or solids.
• Above a certain level, the noise becomes of concern because it may hinder
communication between workers, thus leading to annoyance.
• This in turn may lead to poor job performance and compromise the safety of the worker.
• In addition, excessive exposure to high noise levels may cause loss of hearing.
• It is important to note that exposure to vibration is more than just a nuisance.
• Whereas exposure to vibration may cause discomfort, intense vibration has been known
to cause serious health problems such as back pain, carpal tunnel syndrome (a condition
affecting the hand and wrist) and damage to bones and joints.
• There are two types of occupational vibration: wholebody and handarm vibration.
• Whereas wholebody vibration is transmitted through the supporting surface (feet, back,
etc.), handarm vibration is transmitted to the hands and arms. Examples include: Mining
equipment (wholebody vibration) and Handheld power tools (handarm vibration).
• The hazard associated with a particular type of radiation depends on its energy and ability
to penetrate the body tissue.
• Cosmic, gamma and xray radiation can cause severe damage to the tissue.
• Infrared, ultraviolet, visible light, radio and microwaves on the other hand do not
penetrate appreciably below the skin and the damage is mainly restricted to burns to the
skin and eyes.
• Severe damage to eyes may result from excessive exposure to ultraviolet radiation.
Chemical Hazards in the Workplace
• A large variety of chemical agents are encountered in workplaces due to the diversity of
raw materials and processes used.
• Chemical hazards in such environments arise due to the presence of certain chemical
agents whose properties and/or toxicity may pose a potential risk to the health and safety
of the worker coming in contact with it or handling it.
Chemical hazards may arise in operations involving:
• Compressed gasses
• Flammable and combustible materials 5
• Oxidizing materials
• Poisonous and infections materials
• Corrosive materials
• Dangerously reactive materials
Chemical agents may be present in the air as:
• Fine particles
• Gases and vapors
• Both as particles and vapors at the same time
• Adsorbed or absorbed gases and/or vapors on particles
• In the workplace many hazardous chemicals (ex: chlorine gas are compressed and thus
stored in cylinders under high pressure.
• In using such materials the worker is not only subjected to the chemical hazard but also
the hazards associated with pressure extreme
Flammable and combustible materials
• Such materials may burn readily in the presence of sources of ignition.
• Many organic compounds such as gasoline, solvents, etc. fall in this category.
• These materials can contribute strongly to fire hazards and may possess the ability to
oxidize and thus destroy the biomolecules in living systems.
• Some commonly encountered oxidizers in the workplace include: potassium,
permanganate, hydrogen peroxide, etc.
• Such substances may be dangerous to life in very small amounts. For example, potassium
cyanide, mercury salts.
• Such chemicals cause deterioration of materials including living tissues on contact. Some
examples are, sulfuric acid, potassium hydroxide, etc.
Dangerously reactive materials 6
• The chemicals in this category may undergo rapid or violent reactions under certain
conditions. For example, alkali metals react with water producing highly flammable
The problem with fine particles
• The particles of size less than 5 microns are potentially the most hazardous because of
their effective entry and retention in the lungs.
• The particles are classified as dust, fume and smoke (for solids) and mist (for liquids)
Sources of fine particles include:
• Spray painting (mist)
• Welding (fume)
• Incomplete combustion of oil and grease (smoke)
• Ore grinding (dust)
The problem with gases and vapors
• These may be generated as a result of various operations and can mix and distribute
rapidly throughout the workplace.
• In view of their small size, the gases can readily enter the bloodstream through the lungs
Some sources of potentially toxic gases and vapors include:
• Solvent degreasing (vapors of solvent used)
• Spray painting (vapors of solvent used)
• Welding (gaseous combustion products)
• Biological agents are living organisms, or substances produced by such organisms,