Occupational Asthma Seminar Summary

February 2, 2001
Portland Conference Center
Portland, Oregon

Occupational asthma is a serious problem that affects many Oregonians. Experts were assembled on this problem and this symposium provided useful information for employees and employers on its detection, impacts and prevention.


Occupational asthma is the leading work-related lung disease in the United States. It causes significant morbidity among the working population. It has a huge socioeconomic impact on both workers and their families, and the organizations that employ them. It is also preventable. For these reasons, occupational asthma is an issue that deserves increased attention.

Between 5 and 10% of adults in the United States have asthma. Of these, it is estimated that at least 15% are either caused by or aggravated by the workplace. In the United States, the systems for recognizing and counting cases of occupational asthma are extremely poor. The cases that are identified are considered the ïtip of the icebergÍ, with many, many more cases going unrecognized.

In Oregon, data indicates that 7.7% of adults have active asthma. A study is currently underway to identify more precisely the amount of adult-onset asthma that is associated with exposures in the workplace. Preliminary data indicates that the number of cases related to work is actually closer to 30% of adult-onset asthma cases.

There are three factors needed for occupational asthma to occur. First is an agent capable of causing asthma. Over 250 agents have been identified as causing asthma. These are a broad spectrum of natural and synthetic compounds. With the constant introduction of new products and materials, this number can be expected to rise. Second, there must be sufficient exposure to the agent to actually cause the disease. Finally, a person must be susceptible to developing asthma from the exposure to the agent.

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Occupational asthma in the Pacific Northwest

Occupational asthma is not limited to a few occupations or industries. For example, bakers have developed asthma from flour dust, painters from isocyanate paints, health care workers from powdered latex gloves, and lab technicians from handling animals. Here in the Pacific Northwest, some of the common industries with potential for exposure to asthma causing agents are aluminum refining, hard metals processing (tungsten carbide, cobalt, and nickel), wood products (particularly western red cedar), automotive spray finishing, grain processing, and shell fish processing.


Diagnosing occupational asthma can be a challenge. The health care provider must associate the disease with the workplace. A detailed occupational history must be taken. The pattern of symptoms must be evaluated. It is very common for symptoms to occur only in the evenings of workdays, indicating a delayed response. Other pulmonary illnesses must be ruled out. An exposure assessment is needed to determine what the person is exposed to at work. A case was described in which the Material Safety Data Sheet for the product the patient handled stated it contained no hazardous components. A phone call by the physician to the manufacturer revealed this was not the case - it contained a material well known to cause asthma. If it is available, exposure data for the patient or people doing similar tasks with the same product can be extremely useful. However, good exposure measurements can be difficult to obtain. Identifying the specific causative agent may not be possible, particularly if it is a by-product of a process. If it is identified, accurately measuring the agent may be difficult and costly.

Once an exposure measurement is obtained, there may not be an exposure limit to compare it to. Or the exposure limits published by various organizations may vary widely. The Occupational Safety and Health Administration has permissible exposure limits for many chemicals, but they may not be protective enough for someone who already has asthma. Finally, a chemical may have no recommended exposure limits. In that case, having an accurate measurement may not be particularly useful, except for comparison to other jobs or tasks.

Objective medical tests are available to diagnose asthma, but these are often not used. In the state of Washington, only 57% of workerÍs compensation claims for new onset asthma had objective testing to diagnose asthma, and only 14% of cases had objective testing to attribute the asthma to the workplace. To add to the challenge, there is no clear, universally accepted definition of occupational asthma.

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Workers compensation claims

An additional aspect of this disease is that Workers Compensation claims are rarely made. Of those claims that are made, the denial rate is high. There are many reasons for this, including a failure to recognize that the disease is associated with work, inadequate objective medical tests to prove the disease is caused by work, or simply a fear on the part of the worker that filing a claim will jeopardize his or her employment. There is work aggravated asthma and there is new onset asthma. It is believed that the majority of people with occupational asthma have pre-existing asthma that is aggravated by work. These cases often go unrecognized as occupational asthma for a variety of reasons - objective tests to identify the cause are not done, it is not recognized by either the provider or the patient as related to work, and workers compensation claims are not made. New onset asthma can be of two types. There can be a latency period between the time of initial exposure and the development of asthma. Occupational asthma can also occur without latency - typically after a significant, one-time exposure.

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Managing the disease in the workplace

For those people with asthma, efforts must be made to manage the disease. This typically includes medication, patient education, and control of non-occupational triggers. For those with occupational asthma, the workplace exposure needs to be addressed. If the asthma is induced by a sensitizer, it is prudent to avoid any further exposure to the agent. In the past, this has meant that a worker would be automatically told to leave the job, often with devastating consequences. This does not have to be the only option. One case was presented in which the employer made changes so that the causative agent was used only one day a week, rather than every day. On the day it was used, the patient wore a powered air purifying respirator to prevent exposure. It was a successful solution - the employer retained a trained employee, and the patient kept a job she did was desperate to keep. If the asthma is due to irritant exposure, it is key to reduce exposure to as low as possible. Workers with this type of asthma can tolerate low level exposure to the causative agent. As with sensitzer-induced asthma, an employee may be told to leave a job. However, there are usually relatively simple changes that can be made to reduce exposures to a level that will not put the worker at risk for further breathing problems.

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Workplace modification and prevention

Cases of occupational asthma should be viewed as sentinel events that automatically trigger further action in the workplace. Assume that other people with similar exposures are at similar risk. To prevent further cases, modifications in the workplace can control exposures. Despite an initial investment by the employer, this is actually the most cost-effective way to deal with this issue. Depending on the situation, the change can be quick and inexpensive. For example, purchase a product in a ready-to-use form so the worker does not have to pour a concentrate that results in exposures to the chemical vapor.

Primary prevention is the best way to control occupational asthma. This focuses on preventing cases from ever developing. It is done by performing a risk assessment of the task to anticipate exposure to asthma causing agents. Reviewing the contents of the products, how the products are used, the potential by-products, and actually observing the task are the next steps. A written or verbal description of how something is done may leave out some very important details, so observation is essential. Air samples may be collected to determine actual exposures, if, given their limitations, they are appropriate. Once the risk has been assessed, it can be managed.

Some workplace interventions are extremely simple provided the right questions are asked: Is the task really necessary? Can the product be substituted with a less hazardous product? If the task is done earlier or later in the process, can the exposure be reduced? Can the process be enclosed or isolated from the worker, or can ventilation be used? If nothing else controls it, can respirators be used effectively? Experience has shown that it is crucial to involve both management and workers in the risk assessment and management process. The workers know the task the best and will often have insights for changes that are very effective. They are also much more likely to accept changes if they have been involved in the decision making process.

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Worker education

Perhaps the most effective way to reduce and control occupational asthma is through education. We tend to focus education on the patient. It is important to go beyond this and include all workers potentially exposed to asthma causing agents, their supervisors, and others who can have an impact, such as planners and purchasing agents. The Hazard Communication standard requires that workers be informed of the hazards associated with the products they use and ways to protect themselves from exposure. This is required when an employee is initially assigned to a task and whenever new products are introduced. It has been shown that education programs can actually result in an increase in reported cases of occupational illness. This is not a bad thing. It is an opportunity to use these sentinel cases to focus intervention efforts to prevent new cases from occurring. It may also result in earlier detection of cases so that they can be managed quickly and have the least effect on the worker and the employer.

Occupational asthma is a serious health problem affecting many workers, their families, and their employers. This is a disease that is preventable through control of workplace exposures. Recognizing that until controls are in place, more cases will occur, the medical community, employers, and employees need to work together to reduce the impact of this disease.