Виробнича астма

Symptoms of work-related asthma caused by sensitization to an agent in the workplace typically develop over a latency of weeks to years. Once sensitized, the worker can respond to very low concentrations of the agent, making exposure control challenging for sensitized workers.

Typical symptoms include shortness of breath, chest tightness, wheezing, and cough, temporally related to work. Rhinitis and conjunctival symptoms are more common with high molecular weight allergens and may precede the typical symptoms of asthma by months or years. 

Symptoms typically develop and/or worsen at work after exposure to the sensitizing agent and improve when the patient is away from work (eg, on weekends and holidays). Late asthmatic responses, symptoms starting 4 to 6 or more hours after exposure, are common with low molecular weight agents and can make the association with work challenging to recognize. Continued exposure at work causes the symptoms to become more chronic and persistent, and the association with work can become less apparent. 

• Clarify the diagnosis of asthma (including pulmonary function testing)

• Identify work exposures that are associated with asthma

• Clarify the temporal relationships between asthma and work

Work-related asthma should be considered in all adults with new-onset or worsening asthma. Improvement in asthma symptoms when the patient is away from work (eg, on weekends or holidays) should raise suspicion of work-related asthma. Worsening symptoms or greater use of asthma medications related to work should also prompt further investigation. As the diagnosis of work-related asthma can impact employment, it is important to document the diagnosis of asthma, known or suspected causative agents, and the rationale for work-relatedness.   

Clinicians should note typical symptoms of asthma and clinical improvement in response to inhaled bronchodilators and corticosteroids.

Spirometry may be helpful in establishing a diagnosis of asthma if it shows variable airflow obstruction, which is most commonly demonstrated by improvement in forced expiratory volume in 1 second (FEV1) after taking an inhaled bronchodilator. Improvement in spirometry results after asthma treatment or after removal from triggering exposures and elevation in exhaled nitric oxide also support a diagnosis of asthma.

Asthma is characterized by variable airflow obstruction, so many patients with asthma have normal spirometry results when they are not symptomatic or when they are being treated. Normal spirometry and a lack of response to inhaled bronchodilators do not rule out the diagnosis of asthma, especially when the patient is taking asthma medication or is not symptomatic.

A patient with work-related respiratory symptoms in whom asthma is not documented may have another work-related condition such as vocal cord dysfunction, upper respiratory tract irritation, hypersensitivity pneumonitis, chronic obstructive pulmonary disease (COPD), or chronic bronchitis. Testing may be needed to rule out alternate diagnoses.

Following clarification of the asthma diagnosis, the clinician should document the timing, onset, and progression of asthma in relationship to work and also non-workplace exposures to asthma triggers. A thorough occupational history, including job title, industry, job tasks, and description of the work environment and materials used should be obtained. Asthma becomes more generalized over time, thus in trying to identify the causative factor(s), in addition to evaluating the patient's current symptoms, the clinician should focus on when the patient’s asthma began and/or worsened, especially if the patient is no longer at the workplace in question.

Safety data sheets, mandatory at all work sites in the United States, can be used to identify irritants and allergens that can cause asthma. However, the absence of a known irritant on the safety data sheet does not exclude the diagnosis of work-related asthma. For the few asthma-causing agents for which commercially available allergy testing is available, such as for certain animals and grains, allergy testing can help identify a causative agent, although false negatives and positives are possible. 

Once work and non-work exposures have been characterized, it is important to assess and document the relationship of the patient’s symptoms to work. Serial peak flow measurements taken while the patient is at and also while away from work, changes in inhaler use at and away from work, and allergy testing can provide greater diagnostic certainty. It is more challenging to diagnose work-related asthma once the patient is away from the causative workplace. Thus, unless the patient is having severe symptoms, it is generally preferable not to remove a patient from work while evaluating a possible diagnosis of work-related asthma.  

• Eliminating exposure

• Pharmacologic treatment for asthma

• Workplace modification or change

The pharmacologic treatment of work-related asthma is similar to that of other types of asthma. For all types of work-related asthma, triggering exposures and conditions in the workplace and at home should be minimized. Patients should be monitored for worsening asthma symptoms and increasing medication use.

With sensitizer-induced occupational asthma, once sensitized, patients can react to extremely low levels of airborne exposure. Thus, the recommended management consists of identification of and complete removal from further exposure to the sensitizing agent. Given that complete removal from the workplace can involve substantial socioeconomic consequences, transfer to a different work area at the same workplace or improving engineering controls is sometimes tried. In situations with potential for ongoing exposure to the sensitizer, close monitoring for worsening asthma is essential, including symptoms, medication usage and lung function. Early recognition and prompt removal from the sensitizing agent result in better outcomes, but asthma commonly persists away from the sensitizing agent.

For patients with irritant-induced occupational asthma and work-exacerbated asthma, the hope is that workers can continue their current jobs if adequate measures are implemented to reduce triggering exposures and conditions. These include better engineering controls of irritant exposures and accommodations to avoid certain job tasks or locations, such as work in a hot or cold room. Regular monitoring of asthma symptoms and control is important. If the patient’s asthma worsens at work, further work modifications, including change in employment, may be necessary. Standard asthma treatment, including pharmacologic treatment and minimizing home and environmental triggers, is recommended.  

Both sensitizer-induced and irritant-induced asthma commonly persists even when patients are away from the causative exposure, and patients may require long-term use of asthma medications. Clinicians should document the diagnosis of work-related asthma and specific causative factors before making recommendations about work.

Timely recognition of work-related asthma plays a key role in its further prevention. When a case of occupational asthma is identified in the workplace, the clinician should consider the potential for other workers to be exposed. Communication with the workplace and public health officials facilitates further evaluation and efforts to prevent adverse health effects in co-workers. Reduction or elimination of exposures to occupational sensitizers and irritants, including through the use of occupational hygiene measures such as ventilation and other engineering controls, help to prevent new cases.