Disease: Occupational Asthma

    Occupational asthma facts

    • Asthma is a lung disease characterized by inflammation of the airways and reversible narrowing of the airways, causing shortness of breath, wheezing, chest tightness, and cough.
    • Occupational asthma is asthma that is caused by a specific agent in the workplace.
    • Many different agents can cause occupational asthma.
    • Symptoms can begin immediately with exposure or even years later.
    • Occupational asthma is diagnosed by a thorough history and physical exam, combined with testing of lung function.
    • Treatment mostly involves completely avoiding the offending agent as soon as possible, combined with routine asthma treatments.

    What is occupational asthma?

    Asthma is a chronic lung disease characterized by reversible inflammation of the airways (bronchi). In asthma, white blood cells infiltrate the walls of the airways, increased mucus accumulates within the airways, and the muscles surrounding the airways tighten (constrict or "twitch"), resulting in an overall narrowing of the airways. This narrowing of the airways is responsible for the shortness of breath, wheezing, and chest tightness patients with asthma experience during their attacks. Occupational asthma is a type of asthma that is caused by exposure to a particular substance in the workplace. Occupational asthma is not the same as previously diagnosed asthma that is worsened by being at work (this condition would be called work-aggravated asthma).

    There are two main types of occupational asthma: one type caused by an agent that stimulates the body's immune system that then triggers asthma (immune-mediated); and another where the agent directly irritates the airways (irritant-induced). Immune-mediated occupational asthma typically has a period of time (latency period) between the workplace exposure and the beginning of symptoms. This latency period can be from a few weeks to several years. In contrast, irritant-induced occupational asthma usually causes symptoms immediately after exposure.

    A severe form of irritant-induced occupational asthma is called reactive airways dysfunction syndrome (RADS). This is a condition where the patient suffers a single exposure to a very high concentration of a noxious chemical, usually a gas. A person suffering from RADS will have shortness of breath and chest tightness severe enough to seek medical attention within 24 hours of the exposure. After recovery from the initial massive exposure, the patient will likely have airways that remain excessively responsive or "twitchy" to stimuli from the agent that caused the initial symptoms or other agents. Almost all patients with RADS will have excessively responsive airways for three months, and 50% to 60% will still have excessively responsive airways 18 months later.

    What causes occupational asthma?

    Occupational asthma is caused by exposure to particular inhaled chemicals in the workplace that cause the airways to become excessively responsive. The likelihood of developing occupational asthma seems to be related to the intensity of the exposure to the causative agent. However, it remains unclear whether the intensity of the exposure, the duration of the exposure, or the combination of the two is most important.

    There are numerous agents that can cause occupational asthma. Inhalations of isocyanates, cereal dust, or flour are currently the most common causes of occupational asthma. Agents that cause occupational asthma are usually divided into two different groups: smaller molecules (low molecular weight chemicals), such as isocyanates used in rubber manufacturing, and larger molecules, typically organic substances such as flour. You can find lists of known agents at http://www.hse.gov.uk/asthma/substances.htm.

    What are risk factors for occupational asthma?

    Occupational asthma should be suspected in any adult with new asthma, but most workers who are exposed to potential asthma-causing agents in the workplace do not go on to develop occupational asthma. The patient's individual characteristics, as well as other factors in the workplace environment play a role in the development of the disease.

    One of the main risk factors for occupational asthma is atopy. Atopy is a syndrome characterized by sensitivity to allergens that predisposes an individual to develop occupational asthma. People with atopy often have seasonal allergies or hay fever (allergic rhinitis), chronic inflammation of the nose and sinuses (sinusitis), allergic skin rashes (eczema), and food allergies. People with atopy are not only predisposed to occupational asthma, but they often have non-work-related asthma as well, and their preexisting asthma can be exacerbated by workplace agents (work-aggravated asthma).

    Scientists have also discovered specific genes involved with the immune system that may be associated with a person's risk of developing occupational asthma in response to specific agents, such as isocyanates and dust from western red cedar trees. However, these correlations do not appear to be strong enough to warrant a general screening of people for these genes.

    An important risk factor for occupational asthma, which fortunately can be eliminated, is cigarette smoking.

    If possible, improving ventilation in the workplace may also have a positive impact on the levels of exposures to agents that cause occupational asthma. Although the intensity of exposure is important in the development of occupational asthma, it is less clear if it is the level of agent, duration of exposure, or frequency of exposures that represents the most important factor. Therefore, for most agents, it is difficult to determine what concentration of agent in the air is considered "safe."

    What are symptoms and signs of occupational asthma?

    Symptoms usually begin with wheezing, shortness of breath, and chest tightness weeks to years after workplace exposure. Often, runny nose (rhinorrhea) and inflammation of the lining around the eyes (conjunctivitis) are present as well and may even occur before any wheezing or shortness of breath develops. Occasionally cough with or without phlegm (sputum) production may be present as well.

    Initially, patients may notice that their symptoms are worse at work and better during weekends or holidays away from work. If no action is taken, patients may develop constant symptoms.

    The latency period between the time of exposure to the time of onset of symptoms is highly variable. The latency period for occupational asthma caused by low-molecular weight compounds seems to be shorter than that for high-molecular weight compounds. The latency period for high-molecular weight compounds is often several years. Again, in the case of reactive airways dysfunction syndrome (RADS), symptoms will occur within the first 24 hours of a massive exposure.

    How is occupational asthma diagnosed?

    Your doctor will usually begin with a thorough history and physical examination. Your doctor will likely ask you questions about your symptoms, when they get worse and better, and when they began. It will be important to tell your doctor about your work history, including specifically what you do in the workplace. It's not enough to say, "I work in a restaurant"; your doctor will need to know if you work with flour, clean with chemicals, and what exposures you may have had. Your doctor may ask you to obtain Material Safety Data Sheets (MSDS), which is a form containing data about potential agents. These will generally be on site in your workplace.

    Your doctor may perform a test to measure the flow of air in and out of your lungs, called a pulmonary function test. This test is used to confirm the diagnosis of asthma. This test may involve giving an inhaled medicine called a bronchodilator to relax or dilate the airways. Alternatively, the test may involve administering a medicine to see how excessively responsive, or "twitchy," the airways are (bronchoprovocation test).

    Your doctor may give you a small device called a peak expiratory flow meter to measure your airflow during exhalation both at home and at work. Typically, you will be required to record your results daily for a few weeks to see if there is a difference between airflow when at work and when away from work.

    Sometimes your doctor will examine your sputum (phlegm) for elevated levels of a type of white blood cell called eosinophils. This can help your doctor diagnose both asthma or another type of non-asthma respiratory disease called eosinophilic bronchitis. The respiratory therapist may have you inhale a saltwater solution to help you cough deeply enough to produce sputum from deep in your airways to look for eosinophils.

    Skin tests can be done, where an agent thought to cause your symptoms is introduced below the first layer of skin with a small needle to see if this agent triggers an inflammatory response. However, skin tests are not available for most agents that cause occupational asthma.

    Sometimes pulmonary function tests can be done with a dose of the suspected offending agent used to see if the agent is causing the airway to be excessively responsive. These special pulmonary function tests are usually done at specialized laboratory centers or occasionally they can be done in the workplace environment.

    What is the treatment for occupational asthma?

    The mainstay of treatment for occupational asthma is removal from the exposure. It's important that occupational asthma be diagnosed and the patient avoids further exposure, because most patients with occupational asthma will get worse over time if they remain exposed. This often means changing jobs or changing the particular duty at the workplace.

    Occupational asthma can be treated the same as regular asthma, with inhaled medicines called bronchodilators that open (dilate) the airways as well as inhaled anti-inflammatory medicines (glucocorticoids). However, the most important intervention is to avoid any further exposure.

    Respiratory masks can help reduce the amount of agent that reaches your airway but do not prevent symptoms of occupational asthma.

    What are complications of occupational asthma?

    Over time, the symptoms will become worse if the patient continues to be exposed to the offending agent. After a person becomes sensitized, even very small amounts of the offending agent are capable of triggering significant airway constriction and shortness of breath. The airway constriction (bronchospasm) can be life-threatening if severe and untreated and should prompt quick medical evaluation.

    After avoiding any further exposure, most patients will have improvement in their asthma over a span of months to years, but it is rare that occupational asthma will completely go away. People who were exposed to lower levels of an offending agent for shorter periods of time are more likely to experience eventual improvement in their asthma.

    Can occupational asthma be prevented?

    Occupational asthma can be prevented by monitoring levels of exposure in the workplace, which may help employees from becoming sensitized to the agent. Many potential agents can be monitored continuously. Close monitoring of employee symptoms and prompt removal from the environment once symptoms arise will help prevent occupational asthma complications and maybe reduce its severity. All smokers are advised to quit smoking, and this may help prevent the development of occupational asthma.

    What causes occupational asthma?

    Occupational asthma is caused by exposure to particular inhaled chemicals in the workplace that cause the airways to become excessively responsive. The likelihood of developing occupational asthma seems to be related to the intensity of the exposure to the causative agent. However, it remains unclear whether the intensity of the exposure, the duration of the exposure, or the combination of the two is most important.

    There are numerous agents that can cause occupational asthma. Inhalations of isocyanates, cereal dust, or flour are currently the most common causes of occupational asthma. Agents that cause occupational asthma are usually divided into two different groups: smaller molecules (low molecular weight chemicals), such as isocyanates used in rubber manufacturing, and larger molecules, typically organic substances such as flour. You can find lists of known agents at http://www.hse.gov.uk/asthma/substances.htm.

    What are risk factors for occupational asthma?

    Occupational asthma should be suspected in any adult with new asthma, but most workers who are exposed to potential asthma-causing agents in the workplace do not go on to develop occupational asthma. The patient's individual characteristics, as well as other factors in the workplace environment play a role in the development of the disease.

    One of the main risk factors for occupational asthma is atopy. Atopy is a syndrome characterized by sensitivity to allergens that predisposes an individual to develop occupational asthma. People with atopy often have seasonal allergies or hay fever (allergic rhinitis), chronic inflammation of the nose and sinuses (sinusitis), allergic skin rashes (eczema), and food allergies. People with atopy are not only predisposed to occupational asthma, but they often have non-work-related asthma as well, and their preexisting asthma can be exacerbated by workplace agents (work-aggravated asthma).

    Scientists have also discovered specific genes involved with the immune system that may be associated with a person's risk of developing occupational asthma in response to specific agents, such as isocyanates and dust from western red cedar trees. However, these correlations do not appear to be strong enough to warrant a general screening of people for these genes.

    An important risk factor for occupational asthma, which fortunately can be eliminated, is cigarette smoking.

    If possible, improving ventilation in the workplace may also have a positive impact on the levels of exposures to agents that cause occupational asthma. Although the intensity of exposure is important in the development of occupational asthma, it is less clear if it is the level of agent, duration of exposure, or frequency of exposures that represents the most important factor. Therefore, for most agents, it is difficult to determine what concentration of agent in the air is considered "safe."

    What are symptoms and signs of occupational asthma?

    Symptoms usually begin with wheezing, shortness of breath, and chest tightness weeks to years after workplace exposure. Often, runny nose (rhinorrhea) and inflammation of the lining around the eyes (conjunctivitis) are present as well and may even occur before any wheezing or shortness of breath develops. Occasionally cough with or without phlegm (sputum) production may be present as well.

    Initially, patients may notice that their symptoms are worse at work and better during weekends or holidays away from work. If no action is taken, patients may develop constant symptoms.

    The latency period between the time of exposure to the time of onset of symptoms is highly variable. The latency period for occupational asthma caused by low-molecular weight compounds seems to be shorter than that for high-molecular weight compounds. The latency period for high-molecular weight compounds is often several years. Again, in the case of reactive airways dysfunction syndrome (RADS), symptoms will occur within the first 24 hours of a massive exposure.

    How is occupational asthma diagnosed?

    Your doctor will usually begin with a thorough history and physical examination. Your doctor will likely ask you questions about your symptoms, when they get worse and better, and when they began. It will be important to tell your doctor about your work history, including specifically what you do in the workplace. It's not enough to say, "I work in a restaurant"; your doctor will need to know if you work with flour, clean with chemicals, and what exposures you may have had. Your doctor may ask you to obtain Material Safety Data Sheets (MSDS), which is a form containing data about potential agents. These will generally be on site in your workplace.

    Your doctor may perform a test to measure the flow of air in and out of your lungs, called a pulmonary function test. This test is used to confirm the diagnosis of asthma. This test may involve giving an inhaled medicine called a bronchodilator to relax or dilate the airways. Alternatively, the test may involve administering a medicine to see how excessively responsive, or "twitchy," the airways are (bronchoprovocation test).

    Your doctor may give you a small device called a peak expiratory flow meter to measure your airflow during exhalation both at home and at work. Typically, you will be required to record your results daily for a few weeks to see if there is a difference between airflow when at work and when away from work.

    Sometimes your doctor will examine your sputum (phlegm) for elevated levels of a type of white blood cell called eosinophils. This can help your doctor diagnose both asthma or another type of non-asthma respiratory disease called eosinophilic bronchitis. The respiratory therapist may have you inhale a saltwater solution to help you cough deeply enough to produce sputum from deep in your airways to look for eosinophils.

    Skin tests can be done, where an agent thought to cause your symptoms is introduced below the first layer of skin with a small needle to see if this agent triggers an inflammatory response. However, skin tests are not available for most agents that cause occupational asthma.

    Sometimes pulmonary function tests can be done with a dose of the suspected offending agent used to see if the agent is causing the airway to be excessively responsive. These special pulmonary function tests are usually done at specialized laboratory centers or occasionally they can be done in the workplace environment.

    What is the treatment for occupational asthma?

    The mainstay of treatment for occupational asthma is removal from the exposure. It's important that occupational asthma be diagnosed and the patient avoids further exposure, because most patients with occupational asthma will get worse over time if they remain exposed. This often means changing jobs or changing the particular duty at the workplace.

    Occupational asthma can be treated the same as regular asthma, with inhaled medicines called bronchodilators that open (dilate) the airways as well as inhaled anti-inflammatory medicines (glucocorticoids). However, the most important intervention is to avoid any further exposure.

    Respiratory masks can help reduce the amount of agent that reaches your airway but do not prevent symptoms of occupational asthma.

    What are complications of occupational asthma?

    Over time, the symptoms will become worse if the patient continues to be exposed to the offending agent. After a person becomes sensitized, even very small amounts of the offending agent are capable of triggering significant airway constriction and shortness of breath. The airway constriction (bronchospasm) can be life-threatening if severe and untreated and should prompt quick medical evaluation.

    After avoiding any further exposure, most patients will have improvement in their asthma over a span of months to years, but it is rare that occupational asthma will completely go away. People who were exposed to lower levels of an offending agent for shorter periods of time are more likely to experience eventual improvement in their asthma.

    Can occupational asthma be prevented?

    Occupational asthma can be prevented by monitoring levels of exposure in the workplace, which may help employees from becoming sensitized to the agent. Many potential agents can be monitored continuously. Close monitoring of employee symptoms and prompt removal from the environment once symptoms arise will help prevent occupational asthma complications and maybe reduce its severity. All smokers are advised to quit smoking, and this may help prevent the development of occupational asthma.

    Source: http://www.rxlist.com

    The mainstay of treatment for occupational asthma is removal from the exposure. It's important that occupational asthma be diagnosed and the patient avoids further exposure, because most patients with occupational asthma will get worse over time if they remain exposed. This often means changing jobs or changing the particular duty at the workplace.

    Occupational asthma can be treated the same as regular asthma, with inhaled medicines called bronchodilators that open (dilate) the airways as well as inhaled anti-inflammatory medicines (glucocorticoids). However, the most important intervention is to avoid any further exposure.

    Respiratory masks can help reduce the amount of agent that reaches your airway but do not prevent symptoms of occupational asthma.

    Source: http://www.rxlist.com

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