Health surveillance is the essence of the secondary prevention (Table 4.3). It can be defined as “the set of medical acts, aimed at protecting the health and safety of workers, in relation to the work environment, occupational risk factors and procedures for carrying out work, and at the formulation of the judgment of the specific working task ability.”

In the case of occupational asthma, secondary prevention includes early identification of workers with occupational exposure to asthma-causing agents by means of medical surveillance that consists of preplacement and periodic visits; respiratory questionnaires, with spirometry; immunologic tests; and further investigations to confirm diagnosis and then remove workers from further exposure.

Preplacement visit includes clinical, instrumental, and laboratory investigations aimed at assessing the state of health prior to the occupational hazard exposure and to identify any congenital or acquired abnormalities that may represent a clinical condition of increased respiratory susceptibility toward the irritating, sensitizing, and toxic substances, to which workers will be exposed. It has the aim to define the ability of workers for the specific task. In occasion of the periodic medical examinations, the investigations are designed to check, in the light of actual exposure conditions, the onset of any early and reversible changes of the respiratory system, caused by occupational exposures. Trends of symptom prevalence, suggesting sensitization in relation to different categories of employees, workplaces, and tasks, should be investigated. In this way, it is possible to control the frequency of the occupational allergies [42], to evaluate the risk of occupational disease among the different jobs [43], and to identify sensitizing substances [44, 45].

Health surveillance enables the early identification of adverse health effects in individuals; it may supplement environmental monitoring in assessing control and may contribute to the process of hazard and risk assessment; it offers information regarding hazardous substances to which the employees are exposed, the symptoms which may result, the potential long-term risks, and, therefore, the need to report these symptoms to the occupational health service.

The use of questionnaires seems to be useful in detecting subjects with occupational asthma, and such measures have been introduced in some companies for at-risk workers employed in bakeries, working with animals, detergents, diisocyanates, or complex platinum salts or exposed to acid anhydrides. Studies suggest that such programs are beneficial [46, 47], although the benefit is difficult to precisely specify. It has been suggested that the questionnaire component is likely to be less reliable among respondents who believe that their answers might result in job loss [48, 49].

Some occupations have a higher prevalence of asthma than other occupations. Data of each industry should be collected with the aim of identifying worker populations with a high burden of asthma to which disease prevention efforts should be targeted. Anyway, striking differences are evident comparing results obtained from health surveillance schemes in different countries, such as for England (SHIELD), Finland, Chicago (SENSOR), and Quebec [50]. However, only some of those differences are real, due to the variation on the type and size of the industries, working practices, and environmental protection in the workplace. For example, the high prevalence of occupational asthma in Finland due to animal allergens compared to the other countries may be explained by different farming practice. On the other hand, occupational asthma in Finland is compensated and reports are compulsory, whereas, in the other countries, cases are based on voluntary reporting from hospital and physicians who are unlikely to be consulted by self-employed and uninsured farmers [51].

Physicians should also consider gender differences when diagnosing and treating asthma in working adults. In fact, among adults with work-related asthma, males and females differ in terms of workplace exposures, occupations, and industries. In a study on 8239 confirmed work-related asthma cases, a significant gender difference in the distribution of the disease has been shown; in fact 60 % of them were females. Females were more likely to have work-aggravated asthma and less likely to have new-onset asthma. Females with asthma worked in healthcare and social assistance, educational services, retail trade industries, office and administrative support, education training and library and as healthcare and technical practitioners. Asthma was induced prevalently by miscellaneous chemicals, cleaning materials, and indoor air pollutant in females and miscellaneous chemicals, mineral and inorganic dusts, and pyrolysis products in males [52].

Some authors report that work-related asthma exposures are not discussed between workers and their healthcare provider and this communication gap has implications for asthma management [53]. In any phase the employee must be informed on the specific risks of asthma associated with the occupation and in the control measures to be applied.

The ERS task force guidelines (2012) for occupational asthma [46] recommend that in performing the medical screening and surveillance, the following issues should be performed:

Despite applying primary prevention measures and a proper health surveillance, asthma will affect some workers. Literature reports that the population attributable risk of occupational asthma is between 10 and 25 %, equivalent to an incidence of 250–300 cases per one million people per year [54]. Individual cases need to be carefully investigated and managed. The case management includes the disease monitoring with symptom score, inflammatory and immune biomarkers, and functional parameters (Table 4.4). Among immune biomarkers the usefulness of specific IgE in detecting allergies to organic compounds of HMW is well known. Their useful role has also been reported in allergy to LMW [55]. It has been shown that specific IgE to isocyanates and several other LMW chemicals is more specific than sensitive index of occupational sensitization, and their sensitivity is lower when assayed after cessation of the exposure, with a half-life of 1–2 years [56]. Therefore, specific IgE have a valuable role to play not only in the diagnosis but also in the surveillance of exposed workers, since the persistence of high specific IgE levels may indicate the persistence of exposure [56].

Eosinophil cationic protein (ECP) is a relevant biomarker of eosinophilic inflammation in asthmatic patients [57, 58], and the eosinophilic inflammation is associated with a great decline of FEV1 [59]. However, rather than single determinations, the increase in serum ECP between pre- and post- allergen exposures has a strong correlation with clinical parameters and nonspecific bronchial hyperreactivity [60].

Nonspecific bronchial hyperactivity is indeed an early and sensitive marker of bronchial response to occupational allergens. An increase in nonspecific bronchial hyperreactivity has been found in patients with possible occupational asthma in which the specific bronchial challenge was negative [61].

The optimal management of the occupational asthma and allergies in general is the removal of affected workers from the exposure, which in practice may be difficult to achieve. It includes avoidance of certain tasks and exposures and relocation to other areas or processes within the workplace. Recent papers in literature compared the effectiveness of complete removal from exposure to the causative agent with reduction of exposure and continued exposure in the management of occupational asthma. Results suggested that complete removal from exposure resulted in the best outcome in terms of symptoms, lung function, and airway hyperresponsiveness. Reduction of exposure appeared to be less effective in terms of improving asthma but was also less likely to result in loss of income or unemployment [62]. Some authors reported that a reduction of exposure was associated with a lower likelihood of improvement and recovery of asthma symptoms and a higher risk of worsening of the symptoms and nonspecific bronchial hyperresponsiveness, compared with complete avoidance of exposure [63]. The decline in pulmonary function in asthmatic workers is particularly severe in those unable to avoid allergen exposure. In fact, it has been reported that, despite an optimal pharmacological therapy, the pulmonary function decay slope was steeper in workers continuously exposed to the sensitizing agent (even at reduced level) than in those with a complete cessation of exposure: final FEV1 loss was 512.5 ± 180 ml versus 332.5 ± 108 ml, respectively. The difference became significant after 4 years from the cessation of the exposure. The study shows that the cessation of the exposure to allergen in the workplace appears the most effective measure in limiting pulmonary function decline in asthmatic workers and underlines the importance of allergic risk assessment and control in the management of occupational asthma [64].

Critical analysis of available evidence indicates the following: 1) persistent exposure to the causal agent is more likely to result in asthma worsening than complete avoidance; (2) there is insufficient evidence to determine whether pharmacological treatment can alter the course of asthma in subjects who remain exposed; (3) avoidance of exposure leads to recovery of asthma in less than one-third of affected workers; (4) reduction of exposure seems to be less beneficial than complete avoidance of exposure; and (5) personal respiratory equipment does not provide complete protection [65].

In some cases the causative allergen-inducing asthma is present also outside the workplace and this situation represents a negative prognostic factor. This is the case of latex that affects a large population of healthcare workers [66, 67]. In the occupational setting, latex gloves and other latex-made equipment have been replaced with powder-free latex or nitrile gloves of latex-free compounds with a reduction of latex-induced diseases including asthma [33]. However, although there was improvement after implementation of powder-free latex gloves, there are still a considerable number of healthcare workers with latex-related asthma symptoms, likely due to nonoccupational latex exposure [68].

Recommendations made by the ERS task force on the management of work-related asthma [42] suggest that: