I have previously posted about particulate air pollutants in the workplace:
I’ll continue the theme of potentially harmful air pollutants with a look at volatile compounds.
Let’s start by defining what we mean by volatile compounds.
If you remember your high school chemistry classes, volatile compound are those compounds that vaporize, i.e., phase shift from liquid to gas. Compounds can vaporize via evaporation (e.g., water evaporating from a puddle that dries up following a rain) and boiling (e.g., steam produced by a kettle on the stove – leave it too long and all the water will have fully volatilized into the air leaving you with a black bottomed kettle!). The propensity of a compound to volatilize is a function of the vapor pressure of the compound, for instance at a given temperature, a compound with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.
From an occupational health and safety perspective, most people think of volatile organic compounds (VOCs), but, there are also many volatile inorganic compounds (VICs) that pose hazards for workers and the environment. I think that it is well worth being aware of both types of volatile compounds. As this is a reasonably complex topic I will discuss volatile compounds in two separate blog posts:
Volatile Compounds in the Workplace: Part 2 VICs (this blog post)
For each post. I describe the most common compounds that one might expect to encounter in the workplace, list sources that may lead to elevated levels in the workplace, discuss regulatory issues, describe potential health concerns, and offer suggestions to protect your workers from these hazards.
What are Volatile Inorganic Compounds?
I think this is obvious, these are inorganic compounds (compounds that do not contain molecules of carbon) and easily vaporize, i.e., have a relatively high vapor pressure at room temperature so they will form a gas at room temperature.
Examples of VICs that might be encountered in the workplace are mercury compounds, arsenic compounds, carbon monoxide, chlorine, hydrogen fluoride, phosphine, cyanide compounds, radionuclides, hydrazine, hydrochloric acid, titanium tetrachloride.
Sources of VICs in the Workplace
Volatile inorganic compounds are less commonly encountered than VOCs at most workplaces. Natural sources can arise from forest fires, volcanic activity, etc. Anthropogenic sources of VICs arise most commonly arise from burning of fossil fuels and waste, metal processing, welding, fire suppression systems, and various chemical processes.
Regulations for VICs in the workplace vary widely from country to country. Many developing countries have yet to promulgate legislation for VIC levels in the workplace. Some regulate levels of specific VICs, such as total mercury in the ambient or regulate emissions standards for VICs such as mercury, chlorine and hydrochloric acid. There may also be differences between regulated levels in the workplace vs ambient levels at the property boundary.
Hazards of VIC Exposure
The primary exposure route for VICs is from inhalation of VICs in air. Potential health effects of VIC exposure will vary greatly according to the nature of the compound and the level and duration of exposure.
Some VIC compounds are essentially harmless and others are toxic.
Carbon monoxide and hydrogen cyanide are asphyxiants that lead to the deficient supply of oxygen to the human body, preventing oxygen uptake by cells and leading to unconsciousness and death.
Compounds such as nitrogen oxides, sulphur oxides, hydrochloric acid, and hydrogen halides are irritant gases. Exposure to irritant gases and smoke may cause breathing difficulties with severe pain in eyes, nose, throat and chest, and in some cases lead to death either by impaired vision and preventing escape, or by inhalation of particulate matters which are sufficiently small to penetrate and accumulate in the respiratory tract. Two main effects occur upon exposure to irritants. First, painful sensory irritation occurs immediately in the upper respiratory tract, while lung inflammation and pulmonary oedema occur over a period of time deeper in the lung.
It is up to you to research and understand the hazards posed by the VICs for which your workers may be exposed.
Control of VIC Exposure
The HSE professional much understand the hazards of the specific VICs that their workers may be exposed to and provide information and training specific to the VICs at their site. In general, control systems include appropriate ventilation and exhaust systems combined with appropriate PPE: respiratory protection, proper clothing, gloves, eye protection, etc.
How to Identify and Evaluate Risks of Volatile Compounds
WHO provides solid advice for a systematic approach to identify and evaluate if a potential air contaminant problem exists at your facility. In particular, they propose that if any process is being carried out that released significant amounts of contaminants into the workplace, then an assessment should be made to establish if people are at risk from that exposure.
This assessment is done by looking systematically at the workplace to see whether there is a problem and in general terms what could be done to prevent risk. The assessment should determine which hazardous materials are in use, in what amounts, and how much of which fraction may become airborne and lead to exposure, among other factors. This can include:
- An initial “walk-through” survey of the workplace should be conducted. The walk-through survey will not usually include detailed measurement, although direct-reading instruments may be used to gain a rough picture of the risks present. Obvious and avoidable risks can be dealt with immediately, and schemes exist for using basic substance and use information to decide what controls are appropriate.
- The controls in use should be examined to determine their effectiveness, and the eventual need for other or additional controls should be considered.
- Maintenance and cleaning procedures should be examined, to ensure that they are effective and do not give rise to excessive exposure.
- The position of workers and the organization of their tasks should be appraised in view of the location and nature of the sources of volatile compounds.
- The level of training and information of the workforce should also be assessed. It should be ensured that management favours work practices which reduce or eliminate risks.
- Quantitative evaluations of volatile compounds may be performed for a number of reasons, for example: to assess workers’ exposure in relation to an adopted standard, to determine the need for control measures or to assess the effectiveness of control strategies.
- The results of quantitative evaluations are usually compared with occupational exposure limits. The determination of the contaminant air concentrations to which workers are exposed involves air sampling and further chemical analysis of the collected sample.
- Sampling for exposure assessment is usually carried out by means of a personal sampler, attached to the worker, and which consists of a pump (air mover) and a sampling head located in the worker’s breathing zone.
- Other measurements may be helpful to understand where the volatile compounds are coming from, or at what moment(s) of the work cycle it is being emitted. Often, but not always, the workers involved may be able to say where and when they arise, for instance in some cases from odors.
Of course, if you have any concerns about volatile compounds or any other air quality issues at your facility and/or need assistance in designing and/or carrying out the assessment, feel free to contact us. We will most certainly be pleased to help.
Thanks for reading. Keep safe. Be healthy. Respect your environment.
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Next Week’s Blog Topic: The Sound of Silence: Hazards of a Noisy Workplace!
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