SHOP FLOOR MONITORING

I. It is essential to evaluate the risk that may arise as a result of a worker carrying out a task involving a toxic substance. Let us first define 'hazard' and 'risk', and also 'safe. HAZARD : the adverse consequence to health of contact with a biological, chemical or physical substance or process. This includes energy, like sound, radiation.

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RI»SK : a quantitative measure of hazard. SAFE : something is safe if there is a general acceptance that the risk invoved in its use is a reasonable one.

Thus it is clear that mere presence of a toxic substance does not constitute a risk to health. There are three ways in which health or body can be affected, as follows:-

INHALATION: leading to absortion into the body via the bronchial system or to direct action on the lung itself. SKIN CONTACT: leading to absorptioon into the body by penetration through the skin (like organic lead) or to direct effect on the skin itself (like hexavalent chromium)

INGESTION: leading to direct absorption into the body. Ingestion is an uncommon source of ill health. Most common route of entry into the body is through inhalation of the airborne toxic substance. Standards have been laid for the airborne concentration of different toxic substances such that a person working in an atmosphere containing that level of the toxic substance for 8 hours in a day is unlikely to suffer any risk. These standards are variously called TLV's, Expposure Limits, Permissible Levels in work environment, etc. The unit used for gaseous substances is parts per million or ppm and for particulates and fumes it is milligrams per cubic metre or mg/m . The unit for fibrous substances, like asbestos, is fibres per millilitre or f/ml.

There are various factors that influence effect on humans, as follows:-

1) chemical characteristics toxicity rating physical characteristics-particle size will determine its

deposition in the Respiratory Tree.

For example, particulate contaminants (aerosols) can be classified in two different ways.

PHYSICAL CLASSIFICATION mechancical dispersoid condensation dispersoid dust spray-fume mist fog smoke smog.

PHYSIOLOGICAL CLASSIFICATION nuisance and/or inert inert pulmonary reaction producing minimal pulmonary fibrosis producing extensive pulmonary fibrosis producing chemical irritant systemis poison allergy producing febrile reaction producing.

2) Exposure dose, concentration and volume of administration routee, rate and site of administration duration of freguency

A worker carrying out light work breathes in about 30 litres/m, for medium work about 50 1/m, and for heavy work 80-90 1/m. Thus, in the case of a heavy worker, the intake of the toxic substance will be much higher, and conseguent greater damage to health.

3) Individual susceptibi1ity age, sex, body weight - a larger body will need more oxygen and will

have a higher breathing rate nutritional status (diet factors etc.) presence of disease other habits (smoking, drinking, etc.)

4)Particle deposition in the Respiratory Tree

SITE particle size

nasopharynygeal trachea and bronchial region aleveolar region

5-30 micron 1-5 micron 1 micron

Effects on the body can be of two types:

Acute is an initial short term response to exposure; e.g. carbon monoxide causes confusion, headache. It can be very harmful too.

Chronic is a long term prolonged response; e.g. fibrosis of lung.

Body can excrete toxic substances via the following routes:-in urine from the kidneys expired air from the lungs sweat faeces to a small degree throough hair and nails.

IIMEASUREMENTS It is clearly essential to make measurements of airborne

toxic substances.

Envirotech have developed two simple instruments to make such measurements. They are Personal Sampler Envirotech APM 800 and Handy Sampler Envirotech APM 820 (fig.l and 2 ). Both work off in-built rechargeable Ni-Cad batteries and will sample for minimum 8 hours with ful ly' charged batteries., Both have in-built rotameters also to measure the flow rate; there is a provision for its adjustment.

Personal Sampler is light enough to be carried on one's 'belt with the clip provided. Its sampling head which holds a filter is attached to one's collar or nearby so that the air being sampled is the same as being breathed by the worker. Particulates and fumes etc. will be collected on the filter. At the end of samplling concentration of the pollutant can be calculated from the increase in weight of the filter and the volume sampled.

Handy Sampler can sample gaseous substances also through their absorption in suitable reagents contained in the two impingers connected to the pump. These reagents are analysed at the end of sampling and the concentration of the gases or vapours calculated from the volume sampled.. A sampling head can be connected after the impingers for determination of particulates and fumes etc.

The substance collected on the filter can be further analysed, if required, to determine the concentration of particular pollutants (like metals etc.)

In the case of a fibrous material, like asbestos, a . gridded membrane filter is used for smapling. At the end of sampling a slide of the filter is prepared and the number of fibres on it are counted under a phase contrast microscope.

IllSAMPLING When embarking upon a sampling campaign to asess the risk to which a worker may be exposed, it is necessary to ask several questions, as follows:-

1. What to sample? This involves a review of the materials, processes and operating procedures/work practices, coupled with a discussion with management and safety personnel. A brief 'walk through1 survey can also be useful as a guide to the extent of sampling that may be necessary. When the background work has been completed, it can then be decided, what is to be measured. 2.On whom? The answer to this question obviously depends on the size and diversity of the group of interst. The individual selected must be representative, but selecting the individual with the highest exposure can be a reasonable starting point. If the group is large, then random sampling may have to be employed, but care has to be exercised with this approach.

3.How long do we sample for? Many considerations have to be made when answering this guestion, viz. what are the exposure limits, is the hazard acute or chronic, what is the limit of detection of the method employed, or simply what resources we have at our disposal.

4.How often do we sample? The value of measurement of personal exposure decreases as exposures become further removed from the' exposure limit. For example, regular monitoring where concentrations are below one-tenth or greater than 20 times Exposure Limits are of little value.

5.How many samples should be taken? This is a very important consideration to be made at the initial stage, i.e. when sampling is done for the first time. It must be remembered that one sample may give fortutous, or rogue, result. Therefore, the sample must be repeated until a norm is established. Thereafter, only one periodic sample should be sufficient to assure that all is well. Another very important fact to remember is that it is much more difficult to prove a negative; e.g. the results are always below the Exposure Limit. Initially half a dozen samples will be necessary to substantiate this belief. Once the fact is established, one periodic sample will be enough as long as the result obtained is as expected.

6.How to monitor? The particular strategy to follow is outlined in the-following table:-

Environmental measurements required to determine

Suitable types of measurements

Hazard Personal measurements

dose

Environmental control status

Background monitoring

Whether area is safe to enter Direct reading instrument

IV.CONTROL

l.Once the sampling is completed and the evaluation of results done, it will be necessary to provide remedial measures where the concentrations of polutants are above permissible levels. 2.Following control methods can be employed:-

-substitution with less toxic material -enclosure of harmful process, and making it automatic -isolation of harmful process with appropriate protection for people in that area

-use of a hood with exhaust ventilation and having transparent front/top so that the worker can insert his hands inside to work and be able to see what he is doing -local exhaust ventilation -general ventilation -wet methods (to control dust) -decreasing the daily exposure -Respiratory Protectivee Equipment (RPE), but this should be the last resort, when other control methods are not possible

-personal hygiene -use of protective cream (against effect on the skin) -housekeeping and maintenance -warnings and publicity

3.Success is possible only through Management Commitment and Staff Cooperation. Management will have to allocate financial and manpower resources , and also ensure training of the staff in safer working methods.