Workplace Monitoring

Learning Goals:

1. Learn why different types of monitoring are required for different hazards.
2. Learn the main classifications of monitoring instruments

For workers in the workplace, inhalation is the most common and troublesome exposure route. Exposure via the skin can be prevented with appropriate clothing and equipment. We'll discuses details of this next week. Oral exposure can be eliminated by not eating, drinking, or smoking in the exposure area. Consequently it is most often levels of hazardous and toxic contaminants in the air that are of concern.

Before we get to monitoring contaminants in the air, let's discuss two types of monitoring that don't measure the air, medical surveillance and Biological Exposure Indices (BEIs). Medical surveillance is simply a physical examination and laboratory testing, given by or supervised by a physician. It is required by OSHA for workers exposed to certain types of contaminants. For some contaminants, such as asbestos, there is a definite procedure for medical surveillance. For others, such as a general hazardous waste worker, the procedures are more general, and the physician has more discretion. The examination might disqualify workers based on poor health, but the primary objective is early detection of disease in workers. Medical surveillance is the worst way to learn of problems with excess exposure. The damage is already done. On the other hand, if exposures are kept within the TLV's and PEL's, it is rare to have any adverse findings on the medical surveillance

BEI's, like TLV's are a list copyrighted by the ACGIH. OSHA has incorporated some of these BEI's directly into rules for workers exposed to certain chemicals, but OSHA does not have a list, as such. BEI's measure chemicals, typically in the urine or exhaled air, sometimes in blood, taken from exposed workers. BEI's are useful for certain contaminants, because they measure how much the worker has actually absorbed into his system. Of course for each worker that is related to exposure, but it might be quite different for individuals exposed to the same levels. It also measures accumulation throughout the week. Finally, many contaminants or their harmful metabolites in the body, have sources outside the workplace. The BEI will indicate these. For example, Carbon Monoxide (CO) results in a product, carboxyhemoglobin in the blood. Too much carboxyhemoglobin deprives the worker of oxygen in the tissues. A worker has some direct exposure to CO from polluted air, from CO that is generated in the body by exposure to the solvent methylene chloride, or from smoking cigarettes. While the only exposure the employer is directly responsible for is the methylene chloride in the workplace, the BEI would sum those together.

Monitoring

Protecting the health of workers (and our own) monitoring. The first step is to determine what we are monitoring:

Click on the terms to learn more.

There are two main types of monitoring: Air sampling and Direct reading. Air sampling involves taking a sample of the air and having it analyzed in a laboratory. Direct reading provides some immediate feedback, an alarm or dial reading. Which type of monitoring would you want to use to detect a low oxygen situation. . How about for a gas that is explosive in high concentrations .

Here is web site of a vendor of air sampling devices and supplies, SKC. Note each tab, some for industries, some for processes and some for chemicals. Click on Ambient Air. Eyeball the site then come back here. Here's a site with more links to equipment. Gillian. This SKC pdf has an explanation of the common process, air sampling with personal pump. It involves using a pump to draw air through sampling tubes. In order to calculate the concentrations that were present in the air, the flow rate of the pump must be calibrated exactly and the pumping time known. There are many types of sampling devices, depending on the contaminants you are checking; charcoal is common type of tube. A similar set up, with a filter instead of a sampling tube, is used for particulates, such as asbestos. For particulates, there are devices that separate according to size. For reactive chemicals, there are solutions, and so on - more on our next page.

For regulatory compliance, samples must usually be taken in the breathing zone of workers. Roughly, a fishbowl over the head, at a distance of 6 to 9 inches from the nose and mouth. Typically this means the business end of the sampling device must be attached to the lapel or shirt collar.

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