Monitoring solvent vapour levels

Explaining potential dangers of organic solvent use, and considering control measures and monitoring methods.

by Martin Heels

Many formulations and preparations commonly used in footwear manufacturing contain organic solvents, including adhesives, primers, cleaners, degreasers, inks and finishing agents such as polishes or shoe creams. Measurement of airborne solvent vapour concentrations may be required for a number of reasons, including:

• to help assess possible health risks resulting from work activities
• to assess the effect of changes in materials, procedures or controls
• to determine compliance with occupational exposure limits (OELs)
• to determine the need for, and the effectiveness of, exposure control measures
• to reassure members staff who may be exposed to solvents
• to comply with specific legal requirements.

Several techniques and equipment are available for measuring solvent vapour concentrations. They can all help in the assessment and control of exposure to solvent vapours in the workplace, but it is essential that the appropriate monitoring technique is selected. More importantly, the results should be analysed and interpreted correctly by competent personnel. This is necessary because measurements may form the basis of decisions on possible health risks, compliance with regulations and investment in control measures.

Human health effects

Solvents can enter the human body by three routes of exposure: inhalation, ingestion and skin absorption. Some organic solvents are volatile and will readily form a vapour in air at relatively low temperatures. If uncontrolled, this vapour can cause both short-term (acute) and long-term (chronic) health problems. Some substances commonly used in the manufacture of footwear and apparel include dimethyl formamide, hexane and toluene.

Typical effects of a short-term exposure to solvent vapour include headaches, dizziness, nausea and contact dermatitis. In extreme cases, exposure to very high concentrations of solvents has proved fatal.

Many national health and safety regulations will include requirements to keep exposure to hazardous substances within acceptable limits. In some cases, there is also a requirement to reduce exposure ‘as far as is reasonably practicable’ – that is to say, where the cost of adding additional control measures are reasonable relative to the risk reduction, they should be implemented.

Effective control of solvent vapour releases can also have cost-saving benefits, such as reducing solvent usage and wastage, and by reducing waste disposal costs.

What to measure

As the results of measurements may form the basis of significant decisions on possible health risks, regulatory compliance and investment in suitable control measures, it is important that they are undertaken in a structured manner and that the technique used is appropriate for the process being monitored.

There are three basic types of measurement. Short-term spot measurements are taken over a short period of time, (typically a few minutes), at a single point in the workplace. These will give a rough indication of the concentration levels detected at a particular time and location. This type of monitoring will typically involve the use of chemical indicator tubes.

Average concentration level measurements are particularly useful for measuring personal exposure by sampling air from the working environment. This type of monitoring typically involves the use of solvent vapour monitoring badges.

Continuous measurement at a single location can provide a continuous measure of the concentration level over a particular time and location in the workplace. This will typically involve the use of electronic monitoring instruments.

To demonstrate that exposure levels are not being exceeded, the sample collected, measured or analysed should be representative of the workplace atmosphere. This will give the best indication of the type of control measures or compliance actions necessary to be most effective relative to the application. A number of factors need to be considered prior to selecting an air monitoring technique:

• specificity: The ability to uniquely detect one compound in the presence of other contaminants
• accuracy: How close the results are to the actual concentration present
• sensitivity: The quantity of material that must be present to obtain a result
• cost: The expense associated with the purchase of equipment or supplies, as well as any associated laboratory analysis costs
• ease of use: Whether specific training is required to accurately conduct the test, and how difficult is it to operate the equipment
• calibration: Checks are required to verify that an electronic instrument is performing accurately at the relevant concentration levels.

Solvent vapour levels

Once specific needs have been assessed, and if it has been decided that solvent vapour badge monitoring is the most appropriate method, SATRA can offer a full range of technical services. Solvent vapour monitoring badges can be supplied by SATRA and are designed to be worn by individual operatives who are exposed to solvent vapours during the course of their work. The badges are attached to clothing at the front of their upper body for the duration of the work period. The badges absorb the solvent vapours during a representative typical work period and can be returned to SATRA’s chemical laboratory for analysis.

Interpreting results

All work activities should be subject to periodic risk assessment, which aims to identify hazards and confirm that appropriate control measures are in place. Where solvents are involved, measurement of vapour levels may be necessary as part of an overall risk management strategy.

The results obtained should be supported by and interpreted in light of other information, such as the presence and performance of ventilation systems, observations of work procedures, views and opinions of those conducting the work, and benchmarking against custom and practice within the industry.

Consideration of the results of exposure measurements should identify if immediate action is necessary to eliminate or reduce exposure, whether a programme of planned improvements is needed or if more detailed measurements are required.

Solvent monitoring results should become part of a recognised health and safety management system. The results can be used to demonstrate good practice and to plan, measure and review health and safety issues within the workplace.

Publishing Data

This article was originally published on page 40 of the January 2015 issue of SATRA Bulletin.

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