Occupational exposure to endocrine disruptors and lymphoma risk in a multi-centric European study.

BACKGROUND: Incidence rates of lymphoma are usually higher in men than in women, and oestrogens may protect against lymphoma. METHODS: We evaluated occupational exposure to endocrine disrupting chemicals (EDCs) among 2457 controls and 2178 incident lymphoma cases and subtypes from the European Epilymph study. RESULTS: Over 30 years of exposure to EDCs compared to no exposure was associated with a 24% increased risk of mature B-cell neoplasms (P-trend=0.02). Associations were observed among men, but not women. CONCLUSIONS: Prolonged occupational exposure to endocrine disruptors seems to be moderately associated with some lymphoma subtypes.

Incidence and risk factors for inhibitor development in previously untreated severe haemophilia A patients born between 2005 and 2010.

The objective of this study was to evaluate the inhibitor development (ID) in previously untreated patients (PUPs) with severe haemophilia A (FVIII ≤ 0.01 IU mL(-1) ). All Canadian Haemophilia Treatment Centres completed a questionnaire on patients born between September 2005 and August 2010 and followed for up to 7 years. Eligible patients had at least 20 exposure days (ED) or had developed an inhibitor. The odds ratio (OR) and 95% confidence intervals (95% CI) for risk factors to develop an inhibitor were estimated using unconditional logistic regression. A total of 99 haemophilia A PUPs were studied. Thirty-four (34%) developed an inhibitor (24/34 of high titre). Inhibitors developed in 25/63 (40%) patients with a high-risk mutation. ID was most frequent in Aboriginals (86%). Dose intensity (IU kg(-1)  day(-1) X number of ED) at first exposure to factor VIII (FVIII) was associated with a crude OR increase of 1.10 (95% CI: 0.99-1.23) with each increase of 100 dose-intensity units. Haemarthrosis and intracranial bleeding as the indication for first exposure to FVIII concentrate were associated with a crude OR for ID of 7.63 (95% CI: 2.14-27.17) and 5.08 (95% CI: 1.11-23.31) respectively. ID according to FVIII concentrate used was: Advate (®) 18/50 (36%), Kogenate FS(®) or Helixate FS(®) 15/36 (42%), Wilate(®) 0/11 and Xyntha(®) 1/2. In multivariate analysis, Aboriginal ethnicity (OR = 11.69; 95% CI: 1.11-122.86) and haemarthrosis (OR = 4.49; 95% CI: 1.08-18.61) were statistically significant. The cumulative incidence of ID in severe haemophilia A PUPs was 34% and varied according to ethnicity, type of bleeding at first ED, type of FVIII product and dose intensity at first exposure.

A retrospective cohort study of cancer incidence among patients treated with radiosynoviorthesis.

Radiosynoviorthesis (RS) is an intra-articular injection of a radioactive colloid for the treatment of synovitis administered most often to patients with rheumatoid arthritis or haemophilia. Although highly cost-effective in comparison with surgical or arthroscopic synovectomy, the risk of cancer associated with this treatment is not well known. We evaluated the incidence of cancer in a group of patients treated with RS. A cohort of 2412 adult patients with a variety of underlying conditions (mainly rheumatoid arthritis) and treated with at least one RS between January 1976 and December 2001, was recruited from two centres in Montréal. Cancer incidence and mortality data for cohort members over that time period were obtained from regulatory agencies using linkage. Background rates for all and specific types of cancer were obtained for the provincial (Québec) and national (Canada) population according to age, gender and calendar period categories. Category-specific rates in the cohort were compared with rates in similar categories from the general population generating standardized incidence ratios (SIR). The effects of specific isotope doses and of number of RS treatments were analysed using a Cox-regression model. No increase in the risk of cancer was observed (SIR 0.96; 95% confidence interval 0.82-1.12). There was no dose-response relationship with the amount of radioisotope administered or number of RS treatments. The study provides some indication for the safety of the procedure but homogenous diagnostic groups of younger patients (such as haemophilic patients) receiving RS will need more evaluation.

Peanut allergy: is maternal transmission of antigens during pregnancy and breastfeeding a risk factor?

BACKGROUND: Peanut allergy is an important public health problem in western countries. However, the risk factors associated with this allergy remain uncertain. OBJECTIVE: To determine whether the consumption of peanuts during pregnancy and breastfeeding is a risk factor for peanut allergy in infants. METHODS: We enrolled 403 infants in a case-control study. The cases were infants aged 18 months or less with a diagnosis of peanut allergy based on a history of clinical reaction after exposure to peanuts and the presence of peanut-specific immunoglobulin E. Controls were age-matched infants with no known clinical history or signs of atopic disease. The mothers of the children filled out a detailed questionnaire about maternal diet during pregnancy and breastfeeding, the infant's diet, the presence of peanut products in the infant's environment, and family history of atopy. RESULTS: The mean (SD) age of cases was 1.23 (0.03) years. The groups were comparable in terms of the rate and duration of breastfeeding. However, the reported consumption of peanuts during pregnancy and breastfeeding was higher in the case group and associated with an increased risk of peanut allergy in offspring (odds ratio [OR], 4.22 [95% confidence interval [CI], 1.57-11.30 and OR, 2.28 [95% CI, 1.31-3.97] for pregnancy and breastfeeding, respectively). Overall, the infants with peanut allergy did not seem to be more exposed to peanut products in their environment than the controls. CONCLUSION: Early exposure to peanut allergens, whether in utero or through human breast milk, seems to increase the risk of developing peanut allergy.

Continuing utilisation of specialised health services in extremely preterm infants.

OBJECTIVE: To compare healthcare use from neonatal discharge to 18 months corrected age (CA) of two groups of extremely preterm neonates (23-25 vs 26-28 weeks). DESIGN: Cohort study. PATIENTS: Infants born at < or =28 weeks and admitted in three hospital centres in Quebec, Canada (n=254). MAIN OUTCOME MEASURES: Neurodevelopmental outcomes and healthcare use from neonatal discharge to 18 months CA. RESULTS: Re-hospitalisation rates occurred in 57% of children born at 23-25 weeks and in 49% of those born at 26-28 weeks. In these two age groups, by 18 months, 61% vs 59% were followed in physical or occupational therapy, 29% vs 17% were enrolled in a long-term rehabilitation program, 38% vs 28% used prescribed medication, and 59% vs 33% required medical assistive devices, respectively. Risk of re-hospitalisation was related to bronchopulmonary dysplasia (BPD), severe brain injury, use of home oxygen or an apnoea monitor and older age at neonatal discharge. Multiple births, BPD, severe brain injury, older age at neonatal discharge and single parenthood were associated with risk of using out-patient health services above average (>2 services). CONCLUSION: Extremely preterm children are frequently re-hospitalised during infancy and use a substantial amount of healthcare resources. These results highlight the importance of resource allocation to preterm infants for medical and rehabilitation services after discharge from the neonatal intensive care unit.

Indoor ultrafine particles and childhood asthma: exploring a potential public health concern.

UNLABELLED: Exposure to airborne particulate matter has a negative effect on respiratory health in both children and adults. The ultrafine fraction of particulate air pollution is of particular interest because of its increased ability to cause oxidative stress and inflammation in the lungs. We reviewed the literature, and to date findings suggest that ultrafine particles (UFPs) may play an important role in triggering asthma symptoms. Furthermore, we believe that indoor UFP exposures may be particularly important because people spend the majority of their time indoors where sources of these contaminants are often present. While several epidemiological studies have examined the respiratory effects of ambient UFP exposures, the relationship between indoor UFP exposures and childhood asthma has yet to be examined in clinical or epidemiological studies. However, the portable instrumentation necessary to conduct such investigations is increasingly available, and we expect that this issue will be addressed in the near future. Therefore, the aim of this article is to provide a general review of UFP toxicity as related to childhood asthma in order to draw attention to a potentially important public health concern. PRACTICAL IMPLICATIONS: A number of indoor sources of ultrafine particles (UFPs) have been identified, but the health effects of indoor UFP exposures remain largely unexplored. The potential respiratory effects of such exposures seem most concerning because these particles are known to cause oxidative stress and inflammation in the lungs. Subsequently, indoor UFP exposures may contribute to the exacerbation of asthma symptoms in susceptible individuals. This paper provides a review of UFP toxicity as related to childhood asthma, and to date evidence suggests that further investigation into the respiratory effects of indoor UFP exposures is warranted.

Is metal fume fever a determinant of welding related respiratory symptoms and/or increased bronchial responsiveness? A longitudinal study.

BACKGROUND: The current prospective study investigated the hypothesis of metal fume fever (MFF) being a predictor for the development of respiratory symptoms and functional abnormalities. METHODS: The study consisted of a pre-exposure and two follow up assessments of 286 welding apprentices during an average period of 15 months. A respiratory and a systemic symptom questionnaire, skin prick tests to common allergens and metal salts, spirometry, and methacholine challenge tests were administered. RESULTS: Developing at least one positive skin prick test to a metallic salt solution was found in 11.8% of apprentices. Possible MFF (at least one of fever, feelings of flu, general malaise, chills, dry cough, metallic taste, or shortness of breath) was reported by 39.2% of apprentices. The presence of at least one welding related respiratory symptom (cough, wheezing, or chest tightness) suggestive of welding related asthma was reported by 13.8%. MFF was significantly associated with these respiratory symptoms (OR = 4.92, 95% CI 2.10 to 11.52), after adjusting for age, atopy, smoking, physician diagnosed asthma, and symptoms of non-welding related asthma. Apprentices with possible MFF, and no welding related respiratory symptoms suggestive of welding related asthma at the first follow up, had an increased risk of developing the latter symptoms by the second follow up visit (OR = 7.4, 95% CI 1.97 to 27.45) compared with those not having MFF. MFF was not significantly associated with an increase in bronchial responsiveness. CONCLUSION: MFF could be a predictor for the development of respiratory symptoms but not for functional abnormalities in welders.

Incidence of probable occupational asthma and changes in airway calibre and responsiveness in apprentice welders.

The majority of cross-sectional studies have shown a higher prevalence of ventilatory impairment in welders while only few longitudinal studies were able to detect chronic effects on spirometry or bronchial responsiveness. The aim of the study was to determine the incidence of probable occupational asthma (OA), bronchial obstruction and hyperresponsiveness among 286 students entering an apprenticeship programme in the welding profession. This epidemiological prospective cohort study consisted of a baseline assessment survey and two follow-up assessments. A respiratory symptom questionnaire was administered at each visit. Spirometry and methacholine bronchial challenge test results, conducted once prior to onset of exposure and later after an average of 15 months of apprenticeship, were available for 194 subjects. The incidence of probable OA was approximately 3% (6 of 194). The incidence of bronchial hyperresponsiveness, defined as a > or = 3.2-fold decrease in the provocative concentration causing a 20% fall in the forced expiratory volume in one second from baseline to the end of the study was 11.9%. A statistically significant difference was found between the baseline and end of study for the lung function values. In particular, the forced expiratory volume per cent predicted had significantly dropped by 8.4% on average. The significance of these early pulmonary function changes in relation to possible chronic effects of exposure to welding fumes and gases remains to be explored.

Prevalence and association of welding related systemic and respiratory symptoms in welders.

BACKGROUND: The prevalence of welding related respiratory symptoms coexisting with welding related systemic symptoms in welders is unknown. AIMS: To determine in a sample of welders the prevalence of coexisting welding related systemic symptoms indicative of metal fume fever (MFF) and welding related respiratory symptoms suggestive of occupational asthma (OA), and the strength and significance of any association between these two groups of symptoms. METHODS: A respiratory symptoms questionnaire, a systemic symptoms questionnaire, and a questionnaire on occupational history were administered by telephone to 351 of a sample of 441 welders (79.6%) from two cities in Québec, Canada. RESULTS: The co-occurrence of possible MFF (defined as having at least two symptoms of fever, feelings of flu, general malaise, chills, dry cough, metallic taste, and shortness of breath, occurring at the beginning of the working week, 3-10 hours after exposure to welding fumes) together with welding related respiratory symptoms suggestive of OA (defined as having at least two welding related symptoms of cough, wheezing, and chest tightness) was 5.8%. These two groups of symptoms were significantly associated (chi(2) = 18.9, p < 0.001). CONCLUSION: There is a strong association between welding related MFF and welding related respiratory symptoms suggestive of OA. As such, MFF could be viewed as a pre-marker of welding related OA, a hypothesis that requires further investigation.

Reference values for an index of fetal aortic isthmus blood flow during the second half of pregnancy.

OBJECTIVE: During fetal life, the parallel position of the two cardiac ventricles confers a special status to the aortic isthmus. Flow through the isthmus reflects the balance between the performances of the two ventricles and their respective peripheral impedances. This study proposes a fetal aortic isthmus flow velocity index and its reference values defined on the basis of gestational age (GA). METHODS: Video recordings of 111 normal fetuses from 18 to 39 weeks of gestation were retrospectively reviewed. An isthmus flow velocity index (IFI) was calculated as follows: IFI = (systolic + diastolic)/systolic velocity integrals. GA-specific reference ranges of IFI were constructed. RESULTS: An IFI of 1.33 +/- 0.03 was found at 18 weeks. This value decreased slightly but steadily with GA to reach 1.23 +/- 0.16 at 39 weeks. This change is mainly related to a decrease in diastolic velocity integrals. CONCLUSION: The proposed IFI provides information on the direction and, indirectly, on the volume of blood flow through the fetal aortic isthmus.

Effectiveness of the hands-free technique in reducing operating theatre injuries.

BACKGROUND: Operating theatre personnel are at increased risk for transmission of blood borne pathogens when passing sharp instruments. The hands-free technique, whereby a tray or other means are used to eliminate simultaneous handling of sharp instruments, has been recommended. AIMS: To prospectively evaluate the effectiveness of the hands-free technique in reducing the incidence of percutaneous injuries, contaminations, and glove tears arising from handling sharp instruments. METHODS: For each of 3765 operations carried out in main and surgical day care operating theatres in a large urban hospital, over six months, circulating nurses recorded the proportion of use of the hands-free technique during each operation, as well as other features of the operation. The hands-free technique, considered to be used when 75% or more of the passes in an operation were done in this way, was used in 42% of operations. The relative rate of incidents (percutaneous injuries, contaminations, and glove tears) in operations where the hands-free technique was used and not used, with adjustment via multiple logistic regression for the different risk profiles of the two sets of operations, was calculated. RESULTS: A total of 143 incidents (40 percutaneous injuries, 51 contaminations, and 52 glove tears) were reported. In operations with greater than 100 ml blood loss, the incident rate was 4% (18/486) when the hands-free technique was used and 10% (90/880) when it was not, approximately 60% less. When adjusted for differences in type and duration of surgery, emergency status, noisiness, time of day, and number present for 75% of the operation, the reduction in the rate was 59% (95% CI 23% to 72%). In operations with less than 100 ml blood loss, the corresponding rates were 1.4% (15/1051) when the hands-free technique was used and 1.5% (19/1259) when it was not used. Adjustment for differences in risk factors did not alter the difference. CONCLUSIONS: Although not effective in all operations, use of the hands-free technique was effective in operations with more substantial blood loss.

Incidence and host determinants of work-related rhinoconjunctivitis in apprentice pastry-makers.

BACKGROUND: The authors recently assessed the incidence and determinants of immunologic sensitization to flour in apprentice pastry-makers. The aim of this work was to determine the incidence of work-related rhinoconjunctivitis (RC) symptoms and their determinants. METHODS: For this 188/230 entrants (81.7%) were evaluated before starting exposure to flour, and again 10.8 and 16.8 months after. Questionnaires and skin prick testing to common and work-related allergens were administered at each visit. Bronchial responsiveness to methacholine was assessed at baseline in all subjects and in a subgroup at follow-up. RESULTS: Thirty subjects (16.1%) reported new work-related RC symptoms (13.1 per 100 person-years); in three subjects (1.6%), these were accompanied by incident skin prick test reactivity to flour-derived allergens. Skin prick test reactivity to grass pollens (OR = 3.0, 95% CI, 1.3-6.7) and to pets (OR = 2.5, 95% CI, 1.1-5.9), persistent rhinitis (OR = 3.1, 95% CI, 1.1-8.4), seasonal RC (OR = 2.5, 95% CI, 1.1-5.5), RC on contact with pets (OR = 2.3, 95% CI, 1.03-5.0) and skin prick test reactivity to wheat flour (OR = 10.5, 95% CI, 2.3-46.8), assessed at baseline, were significantly associated with the incidence of work-related RC symptoms. Multivariate logistic regression analysis yielded significant OR of skin prick test reactivity to wheat flour at baseline (OR = 7.1, 95% CI, 1.7-35.1) and persistent rhinitis (OR = 3.9, 95% CI, 1.01-9.6) for the incidence of work-related RC symptoms. Increased bronchial hyperresponsiveness at follow-up was more frequent, although not significantly, in subjects positive to skin prick test to flour on entry and reporting new work-related symptoms (3/5), than in other subjects (4/17). CONCLUSIONS: The incidence of work-related RC symptoms among apprentice pastry-makers was high (16.1% 30/186), while a minority (3/30) also developed skin prick test reactivity to flour. Skin prick test reactivity to wheat flour and persistent allergic rhinitis on starting exposure to flour are significant determinants for the development of work-related RC symptoms.

Host determinants for the development of allergy in apprentices exposed to laboratory animals.

The aim of this study was to evaluate whether determinants of work-related symptoms, skin sensitization and diseases differ between atopic and nonatopic subjects starting a career with exposure to laboratory animals (LA). A cohort of 417 apprentices in animal-health technology was prospectively followed during 32 or 44 months. The effect on the study outcomes of variables derived from questionnaire, skin reactivity, and lung function assessments at baseline were compared in atopic (n=212) and nonatopic (n=183) subjects. Eighty-five incident cases of sensitization to a LA-derived allergen were identified, 67 among atopic and 18 among nonatopic subjects. Baseline rhinitis symptoms in contact with pets and skin sensitization to pets were associated with the development of work-related rhinoconjunctivitis (RC) symptoms in atopic subjects, whereas perannual rhinitis symptoms and having a PC20 (provocative concentration causing a 20% fall in forced expiratory volume in one second) < or = 32 mg x mL(-1) were associated in nonatopic subjects. Baseline rhinitis symptoms on contact with pets and a PC20 value < or = 32 mg x mL(-1) were significant determinants for developing sensitization to a specific allergen in atopic subjects only. Finally, baseline rhinitis symptoms in contact with pets and perannual rhinitis symptoms were associated with the development of occupational RC in atopic subjects, whereas in nonatopic subjects this was associated with having a PC20 value < or = 32 mg x mL(-1). In conclusion, the determinants for the development of specific skin sensitization, symptoms and disease are different between atopic and nonatopic apprentices starting occupational exposure to laboratory-animal-derived allergens.

Individual estimation of exposures to extremely low frequency magnetic fields in jobs commonly held by women.

Exposures to extremely low frequency (ELF) magnetic fields have not been documented extensively in occupations besides the work environments of electric or telephone utilities. A 1980-1993 study of childhood acute lymphoblastic leukemia (ALL) in Québec, Canada, gathered detailed information about the occupations of 491 mothers of ALL cases and mothers of a similar number of healthy controls. This information was combined with published data on the intensities of ELF magnetic fields associated with sources or work environments to estimate ELF magnetic field exposures for a wide range of jobs commonly held by women. Estimated exposures for 61 job categories ranged from 0.03 to 0.68 microT; the 25th, 50th, and 75th percentiles were 0.135, 0.17, and 0.23 microT, respectively. By job category, the most highly exposed jobs (>0.23 microT) included bakery worker, cashier, cook and kitchen worker, electronics worker, residential and industrial sewing machine operator, and textile machine operator. By work environment, the most highly exposed job categories were electronics worker in an assembly plant (0.70 microT) and sewing machine operators in a textile factory (0.68 microT) and shoe factory (0.66 microT). These results provide new information on expected levels of exposure in a wide range of jobs commonly held by women.

Exposure to formaldehyde among animal health students.

The objective of the present study was to evaluate the exposure to formaldehyde in 2 groups each with 18 students in animal health technology from two different training centers (TC) during a 3-hour weekly laboratory session in biology. Personal sampling during the session was done with passive bubblers for formaldehyde. The analysis of formaldehyde was done by visible absorption spectrometry according to NIOSH method 3500. The students in TC 1 were exposed to formaldehyde levels ranging from less than 0.11 to 0.76 mg/m3 with an average at 0.25 mg/m3 during the 3-hour biology laboratory. The students in TC 2 were exposed to higher concentrations of formaldehyde ranging from 0.26 to 1.2 mg/m3 with an average at 0.632 mg/m3. The results of the survey indicate that the students in both centers were exposed to a notable amount of formaldehyde vapor, at a level that is above the threshold limit value.

[Investigation of fetal arrhythmias by simultaneous recording of ascending aortic and superior vena caval blood flow]. / Investigation des arythmies foetales par l'enregistrement simultané des vélocités sanguines dans l'aorte ascendante et la veine cave supérieure.

In a period of 18 consecutive months, all the foetus referred to our Foetal Cardiology Unit for investigation of arrhythmia were systematically assessed by M mode echocardiography and simultaneous recording of blood flow in the superior vena cava and the aorta (SVC/Ao). This study was undertaken to compare the performance of these two approaches. The foetus were classified into three groups according to the arrhythmia diagnosed: Group 1: irregular arrhythmias, Group 2: bradycardias, Group 3: tachycardias. A surface ECG was recorded in all the neonates in whom the arrhythmias persisted. In Group 1, including 50 cases of extrasystoles (49 atrial and 1 ventricular), M mode echo and the Doppler provided the diagnosis in 42 and 47 cases respectively. This difference was not statistically significant. Group 2 comprised four cases of bradycardia (2 blocked atrial bigeminy, 2 complete atrioventricular blocks); the two methods provided the diagnosis in all 4 cases. Group 3 comprised 11 cases including 7 supraventricular tachycardias (SVT), 2 flutter, 1 chaotic atrial rhythm and 1 ectopic junctional rhythm. Complete analysis of these arrhythmias was possible by M mode in 4 cases and by Doppler in all cases. This difference was significant. The distribution of the 7 cases of SVT with respect to the duration of the ventriculoatrial interval was possible by M mode in 2 cases and in all cases by Doppler. This was a decisive factor in the choice of antiarrhythmic therapy. The authors conclude that Doppler and M mode are two echocardiographic approaches which are equally effective in the investigation of foetal atrial extrasystoles and probably of sustained foetal bradycardia. However, Doppler recording of SVC/Ao gives a more detailed and precise diagnosis of more complex foetal arrhythmias.

Natural history of sensitization, symptoms and occupational diseases in apprentices exposed to laboratory animals.

The natural history of the development of sensitization and disease due to high-molecular-weight allergens is not well characterized. This study describes the time-course of the incidence of work-related symptoms, skin reactivity and occupational rhinoconjunctivitis (RC) and asthma (OA); and assesses the predictive value of skin testing and RC symptoms in apprentices exposed to laboratory animals, in a 3-4-yr programme. Four-hundred and seventeen apprentices at five institutions were assessed prospectively with questionnaire, skin-testing with animal-derived allergens, spirometry and airway responsiveness (n=373). Depending on the school, students were seen 8 (n=136), 20 (n=345), 32 (n=355) and 44 (n=98) months after starting the programme. At all visits, the incidence was greater for work-related RC symptoms followed in order by skin reactivity, occupational RC, and, almost equally, OA and work-related respiratory symptoms. The incidence-density figures were comparable for each follow-up period and for most indices up to 32 months after entry into the study and then tended to decrease. The positive predictive values (PPVs) of skin reactivity to work-related allergens for the development of work-related RC and respiratory symptoms were 30% and 9.0%, respectively, while the PPVs of work-related RC for the development of OA was 11.4%. Sensitization, symptoms and diseases occur maximally in the first 2-3 yrs after starting exposure to laboratory animals. Skin reactivity to work-related allergens and rhinoconjuctivitis symptoms have low positive predictive values.

Quantifying and reducing the risk of bloodborne pathogen exposure.

The risk of becoming infected with bloodborne pathogens (e.g., hepatitis B, hepatitis C, HIV) during surgery is real. The degree of risk for perioperative personnel is related to factors that include participating in large numbers of surgical procedures each year; the nature of perioperative work (e.g., use of different types of sharp instruments): exposure to large amounts of blood and body fluids; the prevalence of bloodborne pathogens in the surgical population; the variation in different organisms' ability to be transmitted; the existence of vaccines and the level of vaccination; the availability of postexposure treatment; and the consequences of acquiring the disease. Controlling risks to perioperative personnel can be accomplished by using the Occupational Safety and Health Administration's three methods of control--redesigning surgical equipment and procedures, changing work practices, and enhancing the personal protection equipment of perioperative personnel.

Incidence of sensitization, symptoms, and probable occupational rhinoconjunctivitis and asthma in apprentices starting exposure to latex.

Latex is a well-known sensitizer. Prospective studies in apprentices beginning to be exposed to latex have not been carried out. We wanted to determine the incidence of skin reactivity, cutaneous symptoms, rhinoconjunctivitis (RC) symptoms, respiratory symptoms, probable occupational RC, and asthma in apprentices in dental hygiene. A total of 122 students starting a program in dental hygiene technology were recruited between 1993 and 1995. A questionnaire, skin-prick tests with common aeroallergens and latex, and assessment of spirometry and responsiveness to methacholine were carried out on entry and at follow-up visits at 20 and 32 months after the start of exposure. Of the 110 subjects who participated for at least 1 follow-up visit, skin reactivity to latex developed in 7. Cutaneous symptoms developed in 6 of the 7, RC symptoms developed in 2, and respiratory symptoms developed in 1. Five of the 7 subjects had significant changes in methacholine responsiveness and fulfilled the definition of probable occupational asthma. Sensitized subjects were more likely to be atopic and to have a previous history of asthma and respiratory symptoms on exercise than were nonsensitized subjects. Three subjects at the 20-month assessment and 4 subjects at the 32-month visit showed skin reactivity. The cumulative incidences for skin sensitization, probable occupational RC, and occupational asthma to latex were 6.4%, 1.8%, and 4.5%, respectively.