RADIATION SAFETY

Ionizing & Non-ionizing Radiation:

Electromagnetic radiation consists of varying electric and magnetic fields, operating at right angles to each other. It has both particulate and wavelike aspects. The following table shows the wavelength and frequency of various electromagnetic radiation.

Long waves have low energy, short-waves have high. The higher energy wavelengths (short-waves) are more penetrating i.e. more damaging. X-rays, Gamma rays and cosmic rays have short wavelengths, 10″ cm and less, and high frequency, 10’6 c/s and above and cause ionizing radiation.

Others i.e. electric waves, radio waves, microwaves, visible light, IR, UV and lasers have longer wavelengths and less frequency and cause non-ionizing radiation. Lasers are involved in visible light, IR and UV regions of the spectrum given below:

The Electromagnetic Spectrum
Energy Form	Frequency c/s	Wavelength, cms
Non-ionising radiation :
Electric waves	102 to 104	1012 to 106
Radio waves	104 to 1011	106 to 10-1
Infrared (IR)	1011 to 1014	10-1 to 10-4
Visible light	1015	7×10-5 to 4×10-5
Ultraviolet  (UV)	1015 to 1016	10-5 to 10-6
Ionising radiation :
X-rays	1016 to 1018	10-6 to 10-9
Gamma rays	1018 to 1021	10-10
Cosmic rays	1021 on	10-11 on

Types and Limits of Radiation:

(A) Ionizing Radiation:

Ionizing radiation means electromagnetic or corpuscular radiation capable of producing  ions directly or indirectly in its passage through matter.  It is not visible by normal eyes.  

X-rays, Alpha, Beta, Gamma, fast neutrons, thermal neutrons and radionuclides are ionizing radiation. Radioactive substance (chemical) must be firmly sealed within the metal containers to prevent dispersion to active material into the surrounding.  Radiation hazard means the danger to health arising from exposure to ionizing radiation which may be external or internal.

Animal and human studies have shown that exposure to ionizing radiation can cause carcinogenic, teratogenic or mutagenic effects, as well as other sequelae. The NCRP has formulated exposure limits. Some such limits are given below:

Exposure limits given in rems per year are as under:

Radiation safety levels

Whole-body exposure Long term accumulation	5 (Age in year – 18) x 5
Testicles, Ovaries and Red bone marrow	5
Skin, Thyroid, Bone	15 to 30
Hands, Feet and Ankles	75
Forearms	30
All other organs	15
Pregnant woman, total during pregnancy,	1 0.5 in gestation period
Population          1. Individual 2. Average	0.5 whole body 5 gonads

International Commission on Radiological Protection (ICRP) has prescribed a dose-equivalent limit of 0.5 SV (50 rem) to prevent non-stochastic effects.

Radiation safety measures

Radiation dosimetry in health physics tries to know whether individual radiation exposures are within the permissible dose. Various fixed and portable monitors (detectors and survey instruments) are used for radiation exposure measurement.   Some fixed monitors are as under:

Type of Detector For the type of Radiation.

	Type of Detector	For the type of Radiation.
1	Proportional  or scintillation counter surface barrier diode	Alpha
2	Geiger-Mueller tube or proportional counter	Beta
3	Ionization chamber, scintillation counter	X and Gamma
4	Proportional counter, ionization chamber	Fast neutrons
5	Proportional counter.	Thermal neutrons

Fixed monitors are either area monitoring instruments or contamination monitoring instruments. Area monitors are used for the measurement of air, gamma radiation, neutron radiation, and radioactive effluents.

The contamination monitoring instruments include hand and shoe monitors, portal monitors, clothing monitors and monitors for contaminated wounds. The dosimeters are to be calibrated for proper use.

Best Protection Techniques for radiation:

1. Control of exposure time and distance.
2. Shielding.
3. Wearing a film badge to check the dose limit.
4. Pre and post-employment medical tests.
5. Prevention of radiation disease such as skin cancer, ulceration, dermatitis, cataract, damage to bones and blood, etc.
6. Use of remote-controlled containers.
7. Continuous monitoring and maintaining safe limits by engineering controls and PPE.
8. The sealed container should be leakproof.

Health Physics is a branch of science dealing with the improvement of protection against exposure to ionizing radiation (IR). The main principles of health physics were defined in 1977 by the ICRP.

Three general principles of radiation protection are – (1) justification (2) optimization and (3) limitation of worker’s exposure to radiation.

Medical radiation (x-rays) and nuclear radiation to generate electric power are justified but nuclear weapons for war are not justified.

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Optimization means to keep the exposure as low as achievable

Limitation means to limit the exposure entering a human body by protecting individual or society by devices and observing prescribed safe dose limits.

A record for more than 30 years must be maintained even after completion of the job on ionizing radiation, of (1) doses absorbed by individual and (2) exposure measurement.

In our present-day industry, radiation generating machines and radioactive materials for testing of materials, process control and research have found wide-spread use. X-ray machines are widely used in industry, medicine, commerce and research.

Industrial X-ray devices include radiographic and fluoroscopic units used for the determination of defects in materials in packaged food etc. All such uses are potential sources of exposure. 

The most widely used naturally occurring radio-nuclide is Ra. 226 which is used in medicine and industry. In its use in the medical field, many individuals, besides the patient are potentially exposed to radiation. 

In industry, the principal uses of radium are for radiography in the luminous compounds and in making static eliminators. Textile and paper trades, printing, photographic processing and telephone and telegraph companies are the typical industries where the static eliminator may be found.

The use of artificially produced radio-nuclides (radio-isotopes) in medical, biological, agricultural fields, and scientific research has been increased.

Possible exposure from such radionuclides is involved with their preparation, handling, application and transportation.  Exposures, internal or external, might also arise through contamination of the environment by wastes originating from ‘the use of these materials.

Applications of ionizing radiation in the industry are many. It is used mostly in biological and chemical research, chemical pilot plants and production.

It is used for curing, grafting, testing & evaluation, free radicals, cross .linking, polymerization, disinfection, sterilization, pasteurization etc. Products it is used in semi-conductors, rubber, adhesives, spices, paints and coatings, membranes, fuels, lubricants, plastic piping, enzymes, cosmetics, pharmaceuticals, medical supplies, foods, flooring, furniture, textile, medical uses, agricultural uses etc.

Biological Effects and Controls of Radiation:

Occasional small dose (e.g. X-ray photograph) does not affect much but small doses for a long time or more frequent dose or higher dose may cause biological damage to a human body. Radiation energy passes through a body.

The energy absorbed in a body is called dose. The time between the exposure and the first symptom of radiation damage is called the latent period. The larger the dose or the residence time, the shorter the latent period.

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The human body always generates new cells replacing dead or damaged cells. But when ionizing radiation causes more damage than the body’s repair capacity, biological damage takes place.

Injury to an individual is called a somatic effect and that being passed into future generations is called the genetic effect. the biological effect is the destruction of the reproduction capacity of a cell or carcinogenic effect (cancer) which is difficult to cure.

The biological effect of radiation can be reduced by

1. Shielding the body portion  (especially blood-forming tissues and intestine).
2. Shielding by a portion between the source and the human body by a high-density material such as lead or concrete wall. The thickness should be increased depending on the intensity of radiation.
3. Less dense   (less hazardous)   radiation (electromagnetic instead of charged particles).
4. Low dose rate or fractionation of the dose and decreasing the dose level.
5. Diminishing O₂ concentration in the tissues.
6. Reducing the exposure time.
7. Increasing the distance from the source.
8. Using a sealed source of radiation.
9. Monitoring the environmental exposures by various instruments such as film badge, thermoluminescence dosimeters (TLD), pocket dosimeter, Geiger-MuUer tubes (having automatically audible .alarm), ionizing chambers, neutron and proton monitors and keeping them below the permissible threshold limits. Calibration techniques for instruments is most important.
10. Decontamination facilities.
11. Safe disposal of radioactive wastes.

Medical Surveillance: Exposure to radiation workers may not give any clinical signs. Therefore, according to ICRP, the medical surveillance of radiation workers should aim at-

1. To assess the health of the workers.
2. To preserve good general health standards by monitoring the work conditions, exposure levels and the health of the workers and
3. To provide baseline information in case of accidental exposure or occupational disease.

Functions of such medical service include-

1. Scheduling of medical and radiotoxicological examinations. Pre-employment and during and after (post) employment examinations are necessary.
2. Evaluating the fitness of individual workers for specific tasks.
3. Medical examinations and first-aid after radiation accidents, irradiation or contamination accidents.
4. Keeping adequate medical records for quite a long time (30 years).
5. Contributing to safety and health training and
6. Helping to solve safety problems in the plant.

Large nuclear installations should have full-time and fully equipped medical and health physics services and facilities – including decontamination facilities and ablutions very near the workplace. Small units should obtain part-time facilities.

Personal decontamination facilities include a separate ambulance port, monitoring devices, sink, showers, a disrobing room, clean clothing, and pharmaceutical supplies.

Plant medical services should remain in touch with local and other hospitals where irradicated or contaminated persons can be treated.

Radiological Accidents and Controls: When radioactive irradiation or/and contamination is likely to exceed the maximum permissible levels, such overexposure is termed as radiation accidents.

Accidental external irradiation depends on the nature of radiation, its distribution in space (exposed area), its penetration in the body (dose level) and its duration. In the exposed area irradiation may be of whole-body or partial type.

Dose level may be massive, substantial or slight. The biological effect may be irreversible tissue damage, severe but reversible changes or purely temporary disorders. Kind of radiation may be photon irradiation (x or y- rays), particle irradiation by electrons, neutrons, and protons or mixed photon and particle irradiation.

Accidental radioactive contamination depends on the nature of the radionuclide (its physical, chemical and radioactive characteristics), local distribution in the body (path of entry through skin, wounds or inhalation), duration (initial and secondary impact following bodily intake) and level of contamination (massive, substantial or slight).

Control Measures necessary are –

1. In the case of external irradiation, measurement of exposure in the body and space should soon be carried out to decide a course of action. Urgent treatment is not essential.
2. In the case of radioactive contamination,  urgent treatment is essential. Therapy should first be followed instead of measurement of radioactivity and clinical and biological examinations, though they should be followed subsequently to assess the level of contamination.
3. If the whole-body irradiation is more than 100 rem, the person should immediately be transferred to a specialized hospital.
4. Cases of massive whole-body irradiation are difficult to survive, but, they are mostly rare.
5. No immediate treatment is required for slight or partial irradiation. Persons should be observed for some weeks for subsequent development if any.

Therapeutic measures are as under:

1. Cleaning and washing of skin and wounds.
2. Decontamination by surgical excision, but before that, a strong chelating agent must be applied locally as soon as possible.
3. In case of inhalation, emergency medical treatment becomes necessary if the internal contamination exceeds the maximum 3monthly intake or exceeds (500 x Maximum permissible atmospheric contamination per hour). The person should be transferred to a specialized hospital. In serious accidents, the stomach must be washed out and the contaminant at the intestine should be rendered insoluble.
4. Biological examinations and samplings are necessary. Blood samples must be @ 20 cm³ by volume and raw i.e. without any additive. The first urine sample and next 24-hr samples are necessary. Samples of the first three stools and one 72-hr after the accident are also necessary.
5. To check respiratory contamination,  the person’s handkerchief or nasal samplings by blowing nose into a paper tissue are useful. 6.         Decontamination of substances, objects, and persons.

A card containing information of possible contaminants, the time of sampling and any treatment given before the sampling, must be sent along with the samples to the radiotoxicological laboratory as quickly as possible.

Decontamination: The ionizing radiation cannot be neutralized or interrupted. Therefore rapid decontamination is one of the best safety measures to protect man against possible or actual hazards of direct or indirect radiation. The purpose of decontamination is to reduce its level below the safe level. Following methods of decontamination are used:

1. Mechanical decontamination – removal of radioactive layer by scrubbing shot blasting, washing by water, etc.
2. Physical decontamination – evaporation, dilution, filtration, ultrasonic techniques, or allowing the half-life time if it is in hours or up to 3 days.
3. Chemical decontamination – treating with acid, alkali, chelating compounds, ion-exchange resins etc.
4. Biological decontamination of sewage.
5. Decontamination of water, surface and clothing by selecting appropriate material, e.g. 10% solution of citric acid followed by 0.5% solution of nitric acid to clean stainless steel surface, mineral acids to clean glass and porcelain vessels, replacement of concrete blocks etc. 6.      Decontamination of persons by scrubbing the skin with warm water and soap and followed by the use of surfactants and absorbents. I to 3% solution of hydrochloric and citric acid are also useful. The use of an organic solvent is inadvisable. Cleaning for more than 10 min. is also not advisable, as further cleaning cannot remove the contaminant and may damage the epithelium.

Removal of radionuclides from the human body is much more difficult and needs experienced medical treatment. The choice of a method and reagent depends on the type and character of the contaminant, path of penetration and time elapsed after contamination.

Surgery is the best method to decontaminate wounds. Complexing reagents (viz. DTPA) are generally effective to decontaminate blood, internal organs and tissues. To decontaminate the upper respiratory system, expectorants and vasoconstrictive preparations are prescribed.

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(B) Non-Ionising Radiation:

The main difference between ionizing and nonionizing radiation is that the former is more hazardous because of its higher frequency range and shorter wavelength comparing with the later which has a lower frequency range and longer wavelength.

More safety measures – Decontamination, medical and others- are required to prevent and control the ionizing radiation and its damage.

Non-ionizing Radiation refers to those regions of the electromagnetic spectrum where the energies of the emitted photons are insufficient, under ordinary circumstances, to produce ionization in the atoms of absorbing molecules.

Its lower wavelength limit is 100 nm (arbitrary). It includes ultraviolet, visible light, infrared radiation, microwaves, radio waves, lasers, power frequencies, and radar waves.

The Spectrum Phenomenon: The sun’s energy is transmitted by electromagnetic waves. If a narrow beam of sunlight is passed through a prism and then projected upon a surface, colorful ‘spectrum’ is visible from red at one end through orange, yellow, green, blue, and indigo to violet at the other end.

If a thermometer is moved slowly from violet to the red portion, it shows a rise in temperature. Beyond red (in dark space) it shows a still higher temperature. This dark portion (beyond the red) is called infrared (IR), and the dark portion at the other end (beyond the violet) is called the ultraviolet (UV).

There is no sharp dividing line between IR, visible and UV regions. They differ from each other in frequency, wavelength or energy level. See the table of spectrum in foregoing para.

The common factor among them is that all electromagnetic waves travel at the same speed and are originated from moving electric charges.

Physical & Biological Units: The entire electromagnetic spectrum is roughly divided and studied in two parts:

1. The upper region of shorter wavelength is of more concern to physicists and physical scientists who describe radiation in terms of wavelength.
2. The lower region of longer wavelength is of more concern to communication scientists and engineers who describe radiation in terms of frequency.

Both these units are given in the following table

Physical Units of NI Radiation
Unit	Symbol	Equivalent
Wavelength
angstrom	A	10-8 cm
centimetre	Cm	1 cm
micrometer	mm	10-4 cm
nanometer	Nm	10-7 cm
Frequency
hertz	Hz	1 c/s
kilocycle	Kc	1000 c/s
megacycle	Mc	106 c/s
Gigacycle	Gc	109 c/s

Biological effects of the UV, visible, IR, radiofrequency and the extremely low frequency of power transmission, have been studied.

Visible light and heatwaves can be easily perceived and dark goggles can reduce their intensity to a comfortable level. The UV, IR, microwave and lower frequency radiations cannot be perceived by eyes, but have biological penetration as shown in the following table –

Thermal effects are produced in the skin due to exposure in IR and FM-TV-radio region. Photochemical effects can be produced in the UV and visible regions.

Now, the main divisions of non-ionizing radiation are explained below in brief.

Infrared (IR) Radiation :

The IR region extends from 750 nm to 0.3 cm wavelength of microwaves.

Exposure to infrared radiation is very common in the glass industry and near cupolas and furnaces. Since long-wave infrared radiation is readily absorbed by the surface tissues of the body, it cannot inflict deep injuries in the ‘human body.

Overexposure produces some discomfort which generally gives an adequate warning.  However, the eyes may suffer injuries or general discomfort to other parts of the body, there is some evidence that this may result in cataract.

Infrared (IR) Radiation safety:

The protective measures against this radiation include the placement of reflective screens of polished aluminum shield near the source.

Those screens will direct the rays away from the personnel into unoccupied space or return them to the heat source.

They have been found very effective in many industrial situations.   Eyes of the exposed personnel should always be protected, by suitable glasses, from direct radiation arising from areas that give off intense heat, even though the temperature is not necessarily high. Infrared radiation is measured by the black-bulb thermometer and radiometers.

Main industrial IR exposures are from hot furnaces, molten metal or glass and from arc processes. Use of enclosures, shielding, eye protection, and safe distance are the main safety measures.

Ultraviolet (UV) Radiation :

The UV region is subdivided as Near – 400 to 300 nm. Far – 300 to 200 nm and vacuum -200 to 4 nm.

The effects of ultraviolet radiation are similar to a sunburn.  Since there is a considerable time gap between exposure and development of injury, deep burns, maybe endured without immediate discomfort.

This radiation is readily absorbed in human tissue. As a result, superficial injuries are produced chiefly to the skin and eyes. Higher exposure can cause skin or eye damage. The skin effect is called dermatological and the eye effect is called ocular.

Some industrial processes, such as welding, produce a considerable amount of ultraviolet radiation. In areas where ultraviolet radiation is quite intense, potentially hazardous chemical contaminants, such as ozone and oxides of nitrogen, are also produced due to action of this radiation on air. 

In the zone where arc-welding is carried out, very high concentrations of ozone and oxides of nitrogen have been found.

All personnel engaged in welding should invariably wear goggles and face shields.  Besides these, the use of gloves, leggings, overalls, and boots is an essential necessity for the personnel engaged in welding.

Furthermore, opaque shielding should be used around welding areas to protect other persons. Local exhaust ventilation may also be used as an effective means for the removal of chemical contaminants produced during the arc welding.

Ultraviolet meters can be used for the measurement of .this radiation. It has been suggested that 0.5 microwatts per square centimeter by the permissible limit of ultraviolet radiation for a 7 hours continuous exposure.

The most common exposure to UV radiation is from direct sunlight. Solar irradiation exhibits intense UV radiation but due to the atmosphere (ozone) shielding of the earth (God’s gift), we are not exposed to lethal doses. Long-time exposure to the hottest sunlight (afternoon) may cause skin cancer. This must be avoided.

Some commercial applications of UV radiation are fluorescent lamps, mercury vapor lamps, germicidal lamps, electric arc welding, chemical processing, etched circuit board production, and UV lasers.

Wavelengths below 320 nm cause skin reddening and skin burn (erythemal effect). Solar or UV radiation from artificial sources may cause skin pigmentation (tanning).

Wavelengths between 320 and 230 nm can cause carcinogenic effects.

Main safety measures are shielding of UVR source, use of eye goggles, protective clothing, and absorbing or reflecting skin creams.

Visible Light (Energy) :

This portion lies in the range of 400 to 750 nm. The danger of retinal injury lies between 425 to 450 nm due to peak brightness. Eye response to excessive brightness i.e. partial or full lid closure and shading of the eyes is a protective human mechanism.

The main sources of visible light are the sun, laser beams, arc welding, highly incandescent or hot bodies and artificial light sources such as pulsating light, high-intensity lamps, spotlights, projector bulbs, neon tubes, fluorescent tubes, flash tubes and plasma torch sources.

The visible light is of three types: incident reflected and transmitted light. Incident light is the light that strikes the work surface. The reflected light is that light which bounces off surfaces and reflected onto work surfaces by walls and ceiling. It is measured to determine glare and shadows. Transmitted light penetrates a transparent or translucent material.

Vision is a photochemical and physiological phenomenon. Exposure to glare can cause fatigue of eyes, iritis and blepharism. But these effects cannot cause pathological changes.

Poor illumination can cause industrial accidents. Direct glare, reflected glare from the work and dark shadows lead to visual fatigue. Better lighting provides a safe working environment, better vision and reduces losses in visual performance.

Factors of good lighting are its quantity and quality. The Quantity is the amount of illumination that produces brightness on the task and surroundings. Quality refers to the distribution of brightness in the environment and includes the color of light, its diffusion, direction, degree of glare etc.

Radio and Microwaves :

Within the broad spectrum of radio frequencies, the microwave .region is between 10 to 3 x 105 MHz (megahertz). This form of radiation is propagated from antennas associated with TV transmitters, FM transmitters and radar transmitters.

Uses of microwave radiation are heating sources like microwave ovens, dryers for food products and plywood, pasteurization, ceramics, telecommunications like radio and TV and medical applications (diathermy devices).

Microwave ovens for heating or cooking food are clean, flexible and instantly controllable. The heating rate is very high and the use of any fuel or pollution due to it should be avoided.

Radio or high-frequency electrical heaters are used in metalworking plants for hardening cutting tools, gear-teeth and bearing surfaces and for annealing, soldering and brazing. Use in the food industry is for sterilizing vessels and killing bacteria in foods.

In woodworking plants, high-frequency heating is used for bonding plywood, laminating and general gluing. Other uses include molding plastics, curing and vulcanizing rubber, thermosealing and setting twist in textile materials.

Induction heaters are used for annealing, forging, brazing or soldering conductive materials. Induction furnaces are used in foundries to melt metal. Dielectric heaters are used for non-conducting, dielectric materials like rubber, plastics, leather and wood.

The primary effect of microwave energy is thermal. The higher frequency causes lower hazard and vice versa. Frequencies less than 3000 MHz can cause serious damage. At 70 MHz, the maximum SAR (specific absorption ratio) in humans takes place.

Exposure of high intensity and more time can cause localized damage by skin burning, tissue burns, cataracts, adverse effects On reproduction and even death.

The basic safety measures include restricting energy (power density in microwatts/ m2 and frequency) below the safe level, reducing the time of exposure, shielding and enclosing microwave source, reorienting antenna or an emitting device, use of PPE and controlling at the source.

Power Frequencies:

The main hazards from high voltage lines and equipment (low frequency) are shocks and current. Extremely low frequency (ELF) radiation produces an electric field and magnetic field. An external electric field induces an electric current in the body.

Protection from ELF is possible by shielding of the electric field by any conducting surface. Persons working in high field strength regions (e.g. high voltage lines) should wear electrically conductive clothing. Avoiding entry in such a region is also advisable.

ELF magnetic field cannot be shielded. Therefore the only remedy is to keep the magnetic field below safe levels or to restrict the entry of personnel into the magnetic fields.

Radar:

Radar means “radio detection and ranging”. It is a radio detecting instrument that operates in the radio frequency range from 100 to 105 MHz, echoing in a wavelength range from some meters to millimeters. It consists of a  transmitter and receiver,  usually operating through a common antenna. Power output varies from a few watts to megawatts.

Hazards & Controls: Main hazards associated with radar are as under :

1. Electrical hazards from high voltage equipment.
2. Fire hazards from flammable gases, vapors, explosives, and other materials.
3. Toxic hazards of gas fill in certain waveguides.
4. Thermal effects of electromagnetic radiation.
5. Radioactivity from certain switching tubes.
6. X-rays from high voltage tubes.
7. Material handling hazards in moving portable and fixed equipment.

Control measures include –

1. .Standing near or in front of the antenna should be avoided.
2. Radar workers should not look directly into a radar beam from a high energy unit. High energy is more than 0.01 W/cm2
3. The interior of microwave tubes should be seen through a remote device such as a periscope or telescope.
4. A microwave absorber should be provided to contain beam discharge.
5. Persons should take care to have minimum exposure by keeping a safe distance from the beam.
6. Photoflash bulbs should be properly packed to avoid ignition hazards.
7. Pre current and after employment medical examinations of the radar workers including blood-count and complete eye examination including slit-lamp examination are necessary.

Lasers and Masers :

Laser means “light amplification by stimulated emission of radiation”. The original concept was invented by Dr. Charles Townes in 1955. In 1958, he and Dr. Arthur Schawlou presented a paper on how to make an optical maser.

Maser means “microwave amplification by stimulated emission of radiation”. An optical maser is a laser, therefore, the word laser is mostly used.

Normal light radiates in all directions. Light waves of varying lengths reinforce or cancel each other. Such light is called incoherent. When light waves are made to vibrate in a single plane, made to travel in only one direction and of the wavelength and focused towards a point, a laser beam is obtained. It is called coherent light.

Lasers involve IR, visible and UV regions, concentrate great energy in a point area and can be projected over long distances.

Uses of the laser beam are increasing. Typical areas of laser applications are military, microsurgery, medicine, dentistry, material processing, stack emission analysis to detect air pollution, blood analysis, laser drilling & welding, communications, construction, embryology, geodesy, holography, business offices etc.

Hazards and Controls: It is necessary to understand the type of laser, its power density, the method of usage and its operational aspects to consider laser hazards and controls.

It is not the power (viz. 0.2 watts) but the point source of great brightness which poses a hazard. There are two types of hazards – One from the laser itself and the other from equipment.

The solid-state lasers produce high power outputs and can cause skin burns and eye damage if safety rules are not followed. Other hazards are thermal effect, electric shock, ozone effect, high gas pressures in the flash lamp when it is fired (explosion hazard), cryogenic cool burns due to liquid nitrogen and helium, oxygen deficiency if N or He leaks into the atmosphere, and hazards from viewing, operation and reflections.

The control measures include –

1. Minimization of ocular exposure to the direct laser beam and specular, mirror type, reflections.
2. Education and training of personnel.
3. Shields to prevent accidental exposures.
4. Specially designed eyewear (a major control).
5. Periodical eye examination.
6. A warning sign to be attached to laser equipment.
7. Laser unit in a separate room.
8. Diffuse or retroreflective card targets should be used for short ranges.
9. The laser beam should not be aimed at the flat glass, mirror surfaces or flammable material.
10. Appointment of Laser Safety Officer.

Health hazards depend on the type of material, manufacturing process or work, e.g. poisoning in the pesticide industry, chemical exposure in the chemical industry, fall and hit accidents in the construction industry, finger cutting in the power-press industry and dusting in mine industry.

The modern trend is to consider biological hazards also. The Rules for the Manufacture, Use, Import, Export, and Storage of Hazardous Microorganisms, Genetically Engineered Organisms or Cells are useful in this regard. All these need specialized occupational health services at the workplace.

Depending on classified hazards like fire, explosion, toxic and corrosive effects, fully equipped fire fighting team, medical team and trained personnel with special protective equipment are also essential.

Even if an occupational disease has not occurred, the hazardous exposure at the workplace can reduce the life span slowly and unknowingly.

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