Bacillus subtilis enzymes: a 7-year clinical, epidemiological and immunological study of an industrial allergen

Managing the Risk of Occupational Allergy in the Enzyme Detergent Industry

Enzyme proteins have potential to cause occupational allergy/asthma. Consequently, as users of enzymes in formulated products, detergents manufacturers have implemented a number of control measures to ensure that the hazard does not translate into health effects in the workforce. To that end, trade associations have developed best practice guidelines which emphasize occupational hygiene and medical monitoring as part of an effective risk management strategy. The need for businesses to recognize the utility of this guidance is reinforced by reports where factories which have failed to follow good industrial hygiene practices have given rise to incidences of occupational allergy. In this article, an overview is provided of how the industry guidelines are actually implemented in practice and what experience is to be derived therefrom. Both medical surveillance and air monitoring practices associated with the implementation of industry guidelines at approximately 100 manufacturing facilities are examined. The data show that by using the approaches described for the limitation of exposure, for the provision of good occupational hygiene and for the active monitoring of health, the respiratory allergenic risk associated with enzyme proteins can be successfully managed. This therefore represents an approach that could be recommended to other industries contemplating working with enzymes.

Occupational asthma in female factory worker resulting from exposure to savinase in dishwashing tablets-a case study

OBJECTIVES

Savinase is one of the endopeptidases widely used in washing detergents. Its ability to cause respiratory allergy has been known. Up to now, most cases of occupational asthma (OA) to savinase have been described among workers involved in the manufacture of laundry detergents. We present a case study of 51-year-old female worker of a dishwashing tablets factory, who had been packaging ready-made tablets into foil wrappers for 4 years and developed respiratory symptoms, such as cough, dyspnoea and wheezing.

METHODS

A number of clinical procedures were performed, including the clinical examination, routine laboratory tests, evaluation of total and allergen-specific serum IgE (asIgE) to enzymes, skin prick tests for common allergens, rest spirometry, inhalation methacholine challenge test and a single-blind, placebo-controlled specific inhalation challenge test (SICT) with dishwashing tablets.

RESULTS

Clinical findings and results of routine laboratory tests were within normal limits. Baseline nonspecific bronchial hyperreactivity was revealed. In patient's serum blood we found significantly elevated asIgE to savinase. Decline of FEV1 and PEF in late phase of asthmatic reaction was observed during the specific challenge test. The patient reported chest tightness between 5-12 hours after exposure to dishwashing tablet ingredients. Cytological assessment of an induced sputum revealed increase in the percentage of eosinophils 24 hours after specific challenge in comparison to values noted before the SICT.

CONCLUSIONS

Positive clinical response to the challenge confirmed in objective method tests validated the diagnosis of OA.

Allergic asthma caused by exposure to bacterial alpha-amylase Termamyl®

BACKGROUND

Airborne enzymes behave as potent respiratory allergens. Till date, allergic disorders caused by genetically engineered enzymes widely used in the industry, have not been reported.

RESULTS AND CONCLUSIONS

We describe a worker employed in the detergent industry who developed asthma and rhinitis from IgE-mediated sensitization to the thermostable endo-alpha-amylase Termamyl® and to the protease Savinase®. This is the first report showing that Termamyl® elicits allergic respiratory disorders in humans.

Experiences from occupational exposure limits set on aerosols containing allergenic proteins

Occupational exposure limits (OELs) together with determined airborne exposures are used in risk assessment based managements of occupational exposures to prevent occupational diseases. In most countries, OELs have only been set for few protein-containing aerosols causing IgE-mediated allergies. They comprise aerosols of flour dust, grain dust, wood dust, natural rubber latex, and the subtilisins, which are proteolytic enzymes. These aerosols show dose-dependent effects and levels have been established, where nearly all workers may be exposed without adverse health effects, which are required for setting OELs. Our aim is to analyse prerequisites for setting OELs for the allergenic protein-containing aerosols. Opposite to the key effect of toxicological reactions, two thresholds, one for the sensitization phase and one for elicitation of IgE-mediated symptoms in sensitized individuals, are used in the OEL settings. For example, this was the case for flour dust, where OELs were based on dust levels due to linearity between flour dust and its allergen levels. The critical effects for flour and grain dust OELs were different, which indicates that conclusion by analogy (read-across) must be scientifically well founded. Except for subtilisins, no OEL have been set for other industrial enzymes, where many of which are high volume chemicals. For several of these, OELs have been proposed in the scientific literature during the last two decades. It is apparent that the scientific methodology is available for setting OELs for proteins and protein-containing aerosols where the critical effect is IgE sensitization and IgE-mediated airway diseases.

Relevance of sensitization to occupational allergy and asthma in the detergent industry

There exists considerable historic experience of the relationship between exposure and both the induction of sensitization and the elicitation of respiratory symptoms from industrial enzymes of bacterial and fungal origin used in a wide variety of detergent products. The detergent industry in particular has substantial experience of how the control of exposure leads to limitation of sensitization with low risk of symptoms. However, the experience also shows that there are substantial gaps in knowledge, even when the potential occupational allergy problem is firmly under control, and also that the relationship between exposure and sensitization can be hard to establish. The latter aspect includes a poor appreciation of how peak exposures and low levels of exposure over time contribute to sensitization. Furthermore, while a minority of workers develop specific IgE, essentially none appear to have symptoms, a situation which appears to contradict the allergy dogma that, once sensitized, an individual will react to much lower levels of exposure. For enzymes, the expression of symptoms occurs at similar or higher levels than those that cause induction. In spite of some knowledge gaps, medical surveillance programs and constant air monitoring provide the tools for successful management of enzymes in the occupational setting. Ultimately, the knowledge gained from the occupational setting facilitates the completion of safety assessments for consumer exposure to detergent enzymes. Such assessments have been proven to be correct by the decades of safe use both occupationally and in consumer products.

Defining occupational and consumer exposure limits for enzyme protein respiratory allergens under REACH

A wide range of substances have been recognized as sensitizing, either to the skin and/or to the respiratory tract. Many of these are useful materials, so to ensure that they can be used safely it is necessary to characterize the hazards and establish appropriate exposure limits. Under new EU legislation (REACH), there is a requirement to define a derived no effect level (DNEL). Where a DNEL cannot be established, e.g. for sensitizing substances, then a derived minimal effect level (DMEL) is recommended. For the bacterial and fungal enzymes which are well recognized respiratory sensitizers and have widespread use industrially as well as in a range of consumer products, a DMEL can be established by thorough retrospective review of occupational and consumer experience. In particular, setting the validated employee medical surveillance data against exposure records generated over an extended period of time is vital in informing the occupational DMEL. This experience shows that a long established limit of 60 ng/m(3) for pure enzyme protein has been a successful starting point for the definition of occupational health limits for sensitization in the detergent industry. Application to this of adjustment factors has limited sensitization induction, avoided any meaningful risk of the elicitation of symptoms with known enzymes and provided an appropriate level of security for new enzymes whose potency has not been fully characterized. For example, in the detergent industry, this has led to general use of occupational exposure limits 3-10 times lower than the 60 ng/m(3) starting point. In contrast, consumer exposure limits vary because the types of exposure themselves cover a wide range. The highest levels shown to be safe in use, 15 ng/m(3), are associated with laundry trigger sprays, but very much lower levels (e.g. 0.01 ng/m(3)) are commonly associated with other types of safe exposure. Consumer limits typically will lie between these values and depend on the actual exposure associated with product use.

EAACI position paper on occupational rhinitis

The present document is the result of a consensus reached by a panel of experts from European and non-European countries on Occupational Rhinitis (OR), a disease of emerging relevance which has received little attention in comparison to occupational asthma. The document covers the main items of OR including epidemiology, diagnosis, management, socio-economic impact, preventive strategies and medicolegal issues. An operational definition and classification of OR tailored on that of occupational asthma, as well as a diagnostic algorithm based on steps allowing for different levels of diagnostic evidence are proposed. The needs for future research are pointed out. Key messages are issued for each item.

Agents causing occupational asthma

The workplace is a significant contributor to the burden of asthma. Although the majority of cases probably represent what is labeled work-exacerbated asthma, in a significant number of subjects, asthma is actually caused by 1 or more agents present in the workplace; this is occupational asthma. Two types of occupational asthma are distinguished, according to whether the asthma appears after a latency period. This article discusses (1) two types of agents causing asthma with a latency period and acting through an apparently immunologic mechanism (high-molecular-weight agents and low-molecular-weight agents) and (2) agents causing asthma without a latency period.

Diagnosis and management of work-related asthma: American College Of Chest Physicians Consensus Statement

BACKGROUND

A previous American College of Chest Physicians Consensus Statement on asthma in the workplace was published in 1995. The current Consensus Statement updates the previous one based on additional research that has been published since then, including findings relevant to preventive measures and work-exacerbated asthma (WEA).

METHODS

A panel of experts, including allergists, pulmonologists, and occupational medicine physicians, was convened to develop this Consensus Document on the diagnosis and management of work-related asthma (WRA), based in part on a systematic review, that was performed by the University of Alberta/Capital Health Evidence-Based Practice and was supplemented by additional published studies to 2007.

RESULTS

The Consensus Document defined WRA to include occupational asthma (ie, asthma induced by sensitizer or irritant work exposures) and WEA (ie, preexisting or concurrent asthma worsened by work factors). The Consensus Document focuses on the diagnosis and management of WRA (including diagnostic tests, and work and compensation issues), as well as preventive measures. WRA should be considered in all individuals with new-onset or worsening asthma, and a careful occupational history should be obtained. Diagnostic tests such as serial peak flow recordings, methacholine challenge tests, immunologic tests, and specific inhalation challenge tests (if available), can increase diagnostic certainty. Since the prognosis is better with early diagnosis and appropriate intervention, effective preventive measures for other workers with exposure should be addressed.

CONCLUSIONS

The substantial prevalence of WRA supports consideration of the diagnosis in all who present with new-onset or worsening asthma, followed by appropriate investigations and intervention including consideration of other exposed workers.

Sensitization to Empynase(pronase B) in exposed hospital personnel and identification of the Empynase allergen

BACKGROUND

Empynase is a proteolytic enzyme that is widely used as an anti-inflammatory drug in Korea. We evaluated the prevalence of sensitization to Empynase in association with respiratory allergy symptoms in exposed hospital personnel, and identified the IgE-binding components in the Empynase extract, using sera with high levels of specific IgE antibodies.

METHODS

A total of 154 hospital personnel (135 nurses and 19 pharmacists) who worked in a university hospital and 123 unexposed healthy control subjects were enrolled. A questionnaire was administered that addressed demographics, job category, history of atopic diseases, diverse symptoms including nasal and lower respiratory symptoms, and the association of symptoms with work. Skin prick tests (SPTs) to common aeroallergens and Empynase extract were performed. Empynase-specific IgE antibody was detected by ELISA, and ELISA inhibition tests were conducted. IgE-binding components were identified by SDS-PAGE and IgE immunoblotting.

RESULTS

Forty-two subjects (27.3%) complained of work-related respiratory symptoms (WRRS). Five nurses (3.7%) and one pharmacist (5.3%) had work-related asthma symptoms, and 34 nurses (25.2%) and six pharmacists (31.6%) had work-related rhinitis symptoms. The prevalence of sensitization to Empynase on SPTs was 20.1%, and tended to be higher in pharmacists (31.6%) than in nurses (18.5%). It was estimated that 3.9-8.4% of hospital personnel had WRRS attributable to Empynase. The duration of exposure was longer in positive SPT responders than in negative responders (51.9+/-27.5 vs. 39.2+/-27.3 months, respectively; P<0.05), and the prevalence of Empynase-positive SPTs was significantly higher in subjects with asthma than in those without asthma (57.1% vs. 18.4%, respectively; P<0.05). The levels of Empynase-specific IgE antibodies were significantly higher in pharmacists (76.1+/-83.4 OD units) and nurses (56.3+/-103.0 OD units) than in normal controls (39.8+/-12.7 OD units; P<0.05). Seven subjects (two pharmacists and five nurses) had high serum levels of Empynase-specific IgE antibodies; six of these subjects had WRRS. ELISA inhibition tests were performed with the sera of these six subjects, revealing significant inhibition only with the addition of Empynase. Four strongly staining protein bands (sizes: 36, 33, 16, and 10 kDa) from Empynase extract were observed to bind to the IgE antibodies of sensitized subjects. Conclusion Exposure to Empynase powder may cause rhinitis and asthma in hospital personnel, and the pathogenic mechanism appears to be IgE mediated.

Evidence based guidelines for the prevention, identification, and management of occupational asthma

BACKGROUND

Occupational asthma is the most frequently reported work related respiratory disease in many countries. This work was commissioned by the British Occupational Health Research Foundation to assist the Health and Safety Executive in achieving its target of reducing the incidence of occupational asthma in Great Britain by 30% by 2010.

AIM

The guidelines aim to improve the prevention, identification, and management of occupational asthma by providing evidence based recommendations on which future practice can be based.

METHODS

The literature was searched systematically using Medline and Embase for articles published in all languages up to the end of June 2004. Evidence based statements and recommendations were graded according to the Royal College of General Practitioner's star system and the revised Scottish Intercollegiate Guidelines Network grading system.

RESULTS

A total of 474 original studies were selected for appraisal from over 2500 abstracts. The systematic review produced 52 graded evidence statements and 22 recommendations based on 223 studies.

DISCUSSION

Evidence based guidelines have become benchmarks for practice in healthcare and the process used to prepare them is well established. This evidence review and its recommendations focus on interventions and outcomes to provide a robust approach to the prevention, identification, and management of occupational asthma, based on and using the best available medical evidence. The most important action to prevent cases of occupational asthma is to reduce exposure at source. Thereafter surveillance should be performed for the early identification of symptoms, including occupational rhinitis, with additional functional and immunological tests where appropriate. Effective management of workers suspected to have occupational asthma involves the identification and investigation of symptoms suggestive of asthma immediately they occur. Those workers who are confirmed to have occupational asthma should be advised to avoid further exposure completely and early in the course of their disease to offer the best chance of recovery.

Enzymes as occupational and environmental respiratory sensitisers

A literature review shows that airborne enzymes occurring in the general environment and in purified form in industrial production have a high allergenic potential to the airways, causing rhinitis, conjunctivitis and asthma. It can be assumed that this also applies to the increasing number of enzymes manufactured by the cloning of fast-growing genetically engineered microorganisms. Cross-sectional studies demonstrate exposure-response relations for IgE-mediated sensitisation and airway disorders. Atopic individuals are more susceptible to enzyme allergy than non-atopic individuals. Skin prick testing and measurement of specific IgE antibodies have been shown to be useful diagnostic tools. Very high concentrations of proteases may lead to emphysema. There is also evidence for non-allergic airway inflammation by proteases, probably via protease-activated receptor-2 and intracellular Ca(2+) release. It is recommended that all enzymes be classified with the risk phrase R42 (may cause sensitisation by inhalation) and that their inhalative uptake be totally avoided.

Asthma management in police study

Asthma is a common condition and, therefore, may be seen by the clinical forensic physician and police in widely different circumstances ranging from the autopsy room to roadside breath alcohol testing. This paper concentrates on the assessment and treatment of asthmatics detained in custody and does not refer to the Road Traffic Act provisions. A careful history and objective recording of simple severity markers and peak expiratory flow rate should identify patients who may require hospitalization or urgent treatment. Asthma mortality may be reduced by better understanding of the disease and its treatment and by greater use of prophylactic rather than reliance on relief therapy for bronchospasm.

HLA phenotype and exposure in development of occupational asthma

OBJECTIVE

To review relevant scientific literature to understand the contribution of exposure to the risk of developing occupational asthma and whether HLA class 2 molecules contribute to individual susceptibility to sensitization and asthma caused by low-molecular-weight chemicals.

STUDY SELECTION

The author's expert opinion was used to select relevant articles based on systematic reviews of relevant literature.

RESULTS

Studies during the past decade have shown that intensity of exposure is an important determinant of asthma induced by inhaled respiratory sensitizers, both proteins and low-molecular-weight chemicals. There is evidence that HLA class 2 alleles contribute to the risk of sensitization and asthma caused by low-molecular-weight chemical sensitizers. HLA-DR3 is associated with an increased risk of developing specific IgE to trimellic anhydride (TMA) and complex platinum salts such as ammonium hexachloroplate (ACP). In those exposed to ACP and possibly also to TMA, risk is greater in those who have experienced lower intensity of exposure.

CONCLUSIONS

Exposure intensity is an important determinant of sensitization and asthma caused by respiratory sensitizers. HLA class 2 alleles contribute to individual susceptibility to low-molecular-weight chemicals. For some chemicals, the contribution of HLA class 2 alleles is greater in those less exposed at work to the relevant chemical.

Allergic and latex-specific sensitization: route, frequency, and amount of exposure that are required to initiate IgE production

Quantitative data that documents human exposure-response relationships for IgE sensitization to allergens are limited. Although seemingly straightforward, documentation of exposure-response relationships can be difficult. Issues that are related to study design, allergen standardization, exposure assessment, and evaluation for sensitization can impact greatly on study results. Despite these issues, exposure-response relationships for sensitization to protein allergens have been documented in several occupational groups, which include enzyme-detergent workers, bakers, and laboratory animal workers. In general, atopy acts as an effect modifier in these settings, steepening the exposure-response relationship. Several studies suggest that the greatest risk for sensitization is within the first several years of exposure. For 1 allergen, the protease subtilisin, a short-term exposure limit of 60 ng/m(3) has been recommended by the American Council of Governmental Industrial Hygienists. With regard to natural rubber latex, exposure-related factors such as number of operations have been shown to be risk factors for sensitization of children with spina bifida. By contrast, fewer studies show exposure-response relationships for IgE sensitization of health care workers to natural rubber latex, and the area remains controversial. However, a recent cohort study that evaluated incident sensitization in dental hygiene students suggests strongly that, with sufficient exposure, employment in health care can lead to an increased risk of IgE sensitization to natural rubber latex.

Occupational allergens

Occupational agents are important in a significant number of respiratory diseases. More than 250 occupational substances have been reported to cause occupational asthma. Occupational allergens are the subset of agents causing occupational diseases through an IgE-mediated mechanism. These allergens may be classified as being of either high or low molecular weight. The more common occupational allergens and the industries at increased risk of exposing workers to these agents are discussed.

An outbreak of asthma in a modern detergent factory

The striking decrease in the occurrence of protease-induced occupational asthma in the detergent Industry has been attributed to enzyme encapsulation. We report an outbreak of asthma, at least equal in size to those reported in the 1960s, in a modem European factory which has exclusively used encapsulated enzymes. A survey revealed that enzyme sensitisation and work-related respiratory symptoms were positively correlated with airborne enzyme exposure. We suggest that encapsulation alone is insufficient to prevent enzyme-Induced allergy and asthma.

Occupational airway sensitizers: an overview on the respective literature

BACKGROUND

Worldwide, there is rigorous scientific activity concerning the further development of work safety regulations involving airway-sensitizing substances. Technical directives on hazardous substances are enforced in several countries and are being continuously updated. The European Union has established a code for several occupational substances, now labeled R 42 ("may cause sensitization by inhalation").

METHODS

We present an overview of the literature dealing with allergic occupational asthma. The literature was selected according to criteria of study design and diagnostic test methods. Approximately 300 publications were reviewed including both epidemiological studies and individual case reports.

RESULTS

Airway sensitizers are systematically arranged and separately listed according to chemicals and their origin from animals, plants, and microorganisms. The clinical data as well as threshold limit values (TLV) and R 42 labeling of 250 airway-sensitizing substances are presented.

CONCLUSIONS

The most common sensitizing substances causing occupational asthma were dust of cereal flours, enzymes, natural rubber latex, laboratory animals as well as low molecular substances such as isocyanates and acid anhydrides.

Divergent antibody isotype responses induced in mice by systemic exposure to proteins: a comparison of ovalbumin with bovine serum albumin

Whereas many foreign proteins are immunogenic, only a proportion is associated commonly with allergy, having the potential to induce the quality of immune response necessary for IgE antibody production and the development of immediate type hypersensitivity reactions in the gastrointestinal and/or respiratory tracts. In the context of toxicological evaluations there is a need to identify those properties that confer on proteins the ability to provoke allergic reactions. The characteristics of antibody responses induced in BALB/c strain mice following administration of ovalbumin (OVA), a significant human allergen, have been compared with those provoked by bovine serum albumin (BSA), a protein considered to have more limited allergenic potential. Intranasal or intraperitoneal (ip) administration of BSA or OVA elicited vigorous IgG and IgG1 antibody responses. Differential IgE antibody production was observed, however, with OVA stimulating relatively high IgE antibody titres at all doses tested whereas no or low titre IgE antibody was detected following exposure to BSA. Furthermore, a differential capacity for IgG2a antibody responses was observed, with only BSA provoking high titres of this IgG subclass. The relative quality of induced responses was equivalent following administration of these proteins via mucosal (in) tissue or via a non-mucosal (ip) route of exposure. IgG2a antibody production is promoted by the type 1 cytokine interferon gamma (IFN-gamma), whereas IFN-gamma and the type 2 cell product interleukin 4 exert reciprocal antagonistic effects on IgE antibody responses. Although cytokine expression patterns were not analysed in this series of experiments, the differential IgE and IgG subclass antibody responses induced by BSA and OVA are consistent with the preferential activation of T helper (Th) 1- and Th2-type cells, respectively. These data indicate that proteins can provoke in mice characteristic antibody (IgE and IgG) isotype profiles suggestive of discrete T lymphocyte responses and that such differences may be associated with variable allergenic activity.

Risk of enzyme allergy in the detergent industry

OBJECTIVES

To assess the prevalence of enzyme sensitisation in the detergent industry.

METHODS

A cross sectional study was conducted in a detergent factory. Sensitisation to enzymes was examined by skin prick and radioallergosorbent (RAST) tests. 76 Workers were tested; 40 in manufacturing, packing, and maintenance, and 36 non-exposed people in management and sales departments. The workers were interviewed for work related respiratory and skin symptoms. Total dust concentrations were measured by a gravimetric method, and the concentration of protease in air by a catalytic method.

RESULTS

Nine workers (22%) were sensitised to enzymes in the exposed group of 40, whereas none were sensitised in the non-exposed group. All the sensitised people had symptoms at work; all had rhinitis and one had asthma. Protease concentrations were generally < 20 ng/m3, but occasional peak values up to 80 ng/m3 were detected in the packing and maintenance tasks, and high values of > 1 microgram/m3 in the mixing area.

CONCLUSION

Despite the use of encapsulated enzyme preparations, high enzyme concentrations in workplace air are possible, resulting in a higher risk of sensitisation than expected.

An approach to the diagnosis of occupational asthma

BACKGROUND

Occupational Asthma (OA) is a common disorder attributable to causes and conditions found in the workplace. Occupational asthma may have an immunologic or nonimmunologic basis and may be caused by several hundred agents. A number of factors may increase the risk of developing OA including genetic, industrial, meteorologic, social, and medical factors.

METHODS

The diagnosis is best made by fulfilling well-defined clinical criteria by way of a meticulous and oftentimes arduous evaluation. Pre-existing asthma and allergy, along with other special variants of asthma and unrelated pulmonary disorders which can masquerade as asthma, must be ruled out.

CONCLUSION

Convincing physiologic evidence that demonstrates a cause-and-effect relationship must be obtained before a definitive diagnosis of work-related asthma is made.

Wheat sensitization and work-related symptoms in the baking industry are preventable. An epidemiologic study

A cross-sectional study was conducted among 393 workers from 21 bakeries to study the relationship between wheat allergen exposure and wheat sensitization and work-related allergic symptoms. Exposure to wheat allergens was characterized by a recently developed and validated immunoassay. Specific IgE antibodies against wheat flour and common allergens were measured by immunoassays, and work-related allergic symptoms were registered by questionnaire. A strong and positive association was found between wheat flour allergen exposure and wheat flour sensitization. This relationship was steepest and strongest in atopics. Prevalence ratios for high and medium wheat allergen exposure were 5.2 (95% confidence interval [CI], 1.6-16.2), and 2.7 (0.5-14.5) for atopic workers, and 2.5 (0.8-7.5) and 1.4 (0. 3-6.4) for nonatopics, compared with workers with low wheat allergen exposure. In sensitized bakers those with an elevated allergen exposure had more often work-related symptoms, with prevalence ratios for high and medium wheat allergen exposure of 3.5 (CI 1.6-7. 5) and 2.6 (CI 0.9-7.8), respectively, compared with workers with low wheat allergen exposure. The existence of exposure-sensitization gradients suggests that work-related sensitization risk will be negligible when exposure levels will be reduced to average exposure concentration of 0.2 microgram/m3 wheat allergen or approximately 0.5 mg/m3 inhalable dust during a work shift.

Characteristics of antibody responses induced in mice by protein allergens

Whereas many foreign proteins are immunogenic, only a proportion is also allergenic, having the capacity to induce the quality of immune response necessary to support the production of IgE antibody. We have demonstrated previously that intraperitoneal administration to mice of proteins such as ovalbumin (OVA) or the industrial enzyme A. oryzae lipase, which possess significant allergenic potential, stimulates the production of both IgG and IgE antibody. Identical exposure to bovine serum albumin (BSA), a protein with limited potential to cause immediate respiratory or gastrointestinal hypersensitivity reactions, induced IgG responses only. In the current investigations, the quality of immune responses induced following exposure to these proteins via mucosal tissue (intranasal) has been compared with those provoked following administration via a non-mucosal (intraperitoneal) route of exposure. Intranasal or intraperitoneal administration of BSA, OVA or A. oryzae lipase elicited in each case vigorous IgG and IgG1 antibody responses. For all three proteins, at every concentration tested, and via both routes of exposure, IgG1 antibody titres paralleled closely IgG titres. However, the three materials displayed a differential potential to provoke IgE responses and this correlated with their known allergenic potential in humans. Thus, OVA and A. oryzae lipase stimulated strong IgE antibody responses, whereas BSA provoked low titre IgE only at the highest concentration tested (5% administered intraperitoneally). The quality of induced responses was not affected by the route of exposure. It would appear, therefore, that the stimulation of IgG and IgG1 antibody responses is a reflection of protein immunogenicity whereas protein allergenicity is associated with the induction of strong IgE responses.

Allergy risk in an enzyme producing plant: a retrospective follow up study

OBJECTIVE

To investigate the risk of enzyme sensitisation and clinical allergy in workers exposed to enzymes at Novo Nordisk A/S.

METHODS

The study was a retrospective follow up study based on medical history and test data originally collected at routine screenings for enzyme allergy by the Occupational Health Service (OHS) of Novo Nordisk A/S during the period 1970-92. Workers were exposed to proteases, lipases, cellulases, and carboxyhydrases. Medical records of 3815 subjects were registered in the OHS database. According to criteria including possible enzyme exposure, allergy tests at the time of engagement, and participation in the allergy screening programme 1064 were selected for the present study. Outcomes were allergy symptoms, specific IgE test (radioallergosorbent test (RAST)) to enzymes, skin test reactions to common allergens and enzymes, forced expiratory volume in one second (FEV1), and forced vital capacity (FVC). Potential risk factors were smoking habits, workplace, type of job, age, and sex.

RESULTS

Sensitisation occurred to all types of enzymes handled in the plant, most often in production areas and laboratories; 8.8% developed clinical enzyme allergy during the first three years of employment. The risk declined during the period. The frequency of enzyme sensitisation, expressed as RAST values > 0.5 SU, was 36%, and the frequency of significant RAST values > or = 2 SU was 8%. Ranking diagnoses of enzyme allergy by severity, the frequency of asthma was 5.3%, rhinitis 3.0%, and urticaria 0.6%. Half of the cases occurred within the first 15 months of exposure. Smoking was an independent risk factor for clinical enzyme allergy (odds ratio (OR) = 2.3 (95% exact confidence interval (95% CI) 1.4 to 3.9), measurable RAST > or = 0.5 SU (OR = 1.5 (95% CI 1.1 to 2.1)), and RAST > or = 2 SU (OR = 4.5 (95% CI 2.2 to 8.4)). Atopic predisposition at the time of engagement was not a significant risk factor for enzyme allergy. This could be due to various selection mechanisms.

Occupational asthma

Occupational asthma is a common disorder that may be caused by several hundred agents and has a variety of pathogenetic mechanisms. Level of exposure is an important risk factor, and reduction of exposure is the only certain method of prevention. Atopy and smoking are further risk factors for IgE-mediated asthma but have not been found to increase risk in forms of the disorder that have other mechanisms. The key to diagnosis is a low threshold of suspicion; several investigative procedures can be used to confirm the diagnosis. Many patients suffer from continued asthma despite cessation of exposure; early diagnosis and early removal from exposure are the most important factors for improving the long-term outcome.

Inferences from occupational asthma

Occupational asthma-asthma induced by an agent inhaled at work-provides a valid model for the examination of the more general environmental causes of asthma. In many instances, definable populations exposed to a novel allergen in the workplace at concentrations that are relatively easily measured develop IgE-associated asthma and characteristic eosinophilic bronchitis. Carefully designed epidemiological studies suggest that the incidence of IgE antibody and asthma is highest in the first one to two years of exposure; and that the risk is directly related to the intensity of airborne allergen exposure. The relationship between exposure and outcome is modified both by concurrent cigarette smoking and by genotype, although the details of this latter interaction remain unclear. Symptoms, airway hyper-responsiveness and airway inflammation may persist for several years after avoidance of exposure to the initiating agent. If the relevance of the model is accepted then these insights require testing and further investigation, both within the field of occupational asthma and, by extension, in the wider field of asthma in the general environment.

Enzyme exposure and enzyme sensitisation in the baking industry

OBJECTIVES

To assess the exposure to enzymes and prevalence of enzyme sensitisation in the baking industry.

METHODS

A cross sectional study was conducted in four bakeries, one flour mill, and one crispbread factory. Sensitisation to enzymes, flours, and storage mites was examined by skin prick and radioallergosorbent (RAST) tests. 365 workers were tested. The workers were interviewed for work related respiratory and skin symptoms. Total dust concentrations were measured by a gravimetric method, and the concentration of alpha-amylase in air was measured by a catalytic method. An immunochemical method was used for measuring cellulase and xylanase in air.

RESULTS

Total measured dust concentrations were from 0.1 to 18 mg/m3, with highest values in dough making areas of bakeries. The alpha-amylase concentrations generally followed the total dust concentrations and reached the highest values < 6.6 micrograms/m3 in the same areas. Cellulase and xylanase varied with concentrations < 180 ng/m3 and < 40 ng/m3, respectively, in the flour mill and the crispbread factory. No cellulase, but concentrations of 1-200 ng/m3 xylanase, were found in the bakeries, probably indicating the natural xylanase activity of wheat. 12 workers (8%) in the bakeries, three (5%) in the flour mill, and four (3%) in the crispbread factory were skin prick positive to enzymes. The corresponding percentages of positive reactions to flours were 12%, 5%, and 8%.

CONCLUSIONS

The study confirmed that industrial enzymes in baking used as additives in a powdered form pose a risk of sensitisation. The no effect air concentrations for industrial enzymes are not known. Based on present knowledge, however, lowering exposures and eliminating short and high peaks by technical measures would lower the risk of sensitisation. This would be most effectively accomplished by shifting to non-dusty products.

Irritant-induced occupational asthma

A retrospective review was performed on the files of 154 consecutive workers assessed for occupational asthma to clarify the relative frequency of asthma induced by irritants in the workplace and to determine whether such asthma was clearly distinguishable from other forms of occupational asthma. Fifty-nine workers were considered to have occupational asthma. A subset of ten had a history consistent with asthma initiated by exposure to high concentrations of an irritant, had persistent symptoms for an average of five years when seen, demonstrated increased reactivity to methacholine, and gave no prior history of pulmonary complaints. These ten had a lower incidence of atopy (20 percent vs 58 percent) and a more frequent history of smoking (80 percent vs 38 percent) than the other subjects with occupational asthma but did not differ in average latency (5.9 years vs 5.7 years). Our findings suggest that irritant-induced asthma is not uncommon, and those affected may have different baseline characteristics from others with occupational asthma.

Identification of immunotoxic effects of chemicals and assessment of their relevance to man

Immunotoxicity is defined as the adverse effects of foreign substances (xenobiotics) on the immune system. Two types of effects are possible: immunosuppression (which may result in an increased susceptibility to infection or to the development of tumours) and immunopotentiation (which may manifest as an allergy or as autoimmunity). There is, as yet, little evidence that well controlled occupational exposure to industrial chemicals has led to clinically significant immunosuppression. In contrast, a number of industrial chemicals have been shown to cause immunopotentiation in exposed populations, producing occupational asthma and contact dermatitis and possibly autoimmunity. In experimental models, immunosuppression (usually assessed by in vivo or in vitro immune function tests) has been induced by a wide range of chemicals but there are a few reports of the immunosuppression leading directly to an increased susceptibility to infection or to the development of tumours. Predictive experimental models are available for type IV allergic reactions, but the identification of chemicals that have a potential to cause other types of allergy or autoimmune reactions requires further research and the development and validation of new animal models. It is considered that routine subacute and chronic toxicity studies should include a full gross and histopathological assessment of the lymphoid organs to more accurately detect the potential of a chemical to cause immunotoxicity. Should such studies indicate that a substance has affected the immune system directly, an assessment of overall immune competence and function tests may be necessary using dose levels below those which cause frank toxicity. However, precise interpretation of immune function tests in terms of their relevance to human health requires an improved understanding of the extent of the functional reserve of the immune system. A strategy for assessing immunotoxicity in exposed human populations demonstrates a need for reliable clinical assessment, accurate medical record-keeping, an environmental and biological monitoring for levels of contaminating chemicals and the judicious use of well-validated immune function tests.

Occupational asthma

A brief review of the definition, prevalence, predisposing factors, clinical features and possible causes of occupational asthma is presented, together with an overview of the appropriate steps in the management of this condition. In terms of the prognosis, the need for effective prevention and early detection of sufferers is emphasized.

Lack of allergic reactions in workers exposed to Pruteen (bacterial single-cell protein)

Men exposed to high concentrations of bacterial single-cell protein (Pruteen) dust have complained of "sticky eyes" and influenza-like symptoms. Over four years, surveillance of a work force of 70 men with a programme that included a respiratory health questionnaire, skin prick testing, serum testing for precipitating antibodies, lung function measurements, and chest radiography has shown no evidence of allergic reaction or of exposure-related deterioration in lung function. The symptoms experienced may be attributable to exposure to lipopolysaccharide. The results show that Pruteen can be produced and handled without adverse effects on health, provided that adequate measures are taken to prevent exposure to high concentrations of dust.

Detergent enzymes and occupational safety. Observations on sensitization during Esperase production

During a 10-year survey of 667 workers producing the detergent enzyme Esperase, derived from an alkolophilic strain of Bacillus licheniformis, 31 were found to have been sensitized. All but one were at the same time sensitized to subtilisins, with which they also had been working. No distinction could be made between symptoms attributed to Esperase and symptoms attributed to enzymes derived from Bacillus subtilis (licheniformis) or other enzymes. Symptoms, when present, were mainly from the lower respiratory tract. Nine sensitized workers were symptom-free. Sensitization was by IgE antibodies and detected by the RAST test. Twenty-one sensitized workers were transferred for precautionary measures or left the company. All 26 sensitized workers, whom it was possible to follow and reinvestigate, were no longer RAST-positive. Ten workers remained in their jobs. No signs of deteriorating lung function or permanent lung damage were found. The study indicated that, when strictly enforced, recommended operating procedures for workers handling hitherto well-known detergent enzymes are sufficient for dealing with Esperase. The data suggest there is no significant risk of consumer sensitization.