Health hazards due to the inhalation of amorphous silica.

Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic ("thermal" or "fumed") silica, and (3) chemically or physically modified silica. According to the different physicochemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or emphysema cannot be excluded. There is no study that allows the classification of amorphous silica with regard to its carcinogenicity in humans. Further work is necessary in order to define the effects of amorphous silica on morbidity and mortality of workers with exposure to these substances.

Effectiveness of a medical surveillance program for the prevention of occupational asthma caused by platinum salts: a nested case-control study.

BACKGROUND: Exposure reduction has proven to be effective in the prevention of occupational asthma. Few data are available on the effectiveness of secondary prevention programs, including medical examinations and removal of workers from exposure sources after detecting symptoms or signs indicative of a beginning disease. OBJECTIVE: We sought to assess the effectiveness of a medical surveillance program in workers with exposure to platinum salts. METHODS: A nested case-control study was performed in 14 workers of a catalyst production plant whose skin prick test (SPT) responses to platinum salt converted from negative to positive during a 5-year prospective cohort study with yearly medical examinations and 42 matched control subjects from the plant who did not experience SPT response conversion. With the exception of 2 subjects, the workers showing SPT response conversion were removed completely from exposure sources and followed for up to 42 months. RESULTS: Work-related new symptoms were reported by 9 of the 14 subjects, and new symptoms without relation to work were reported by 3 subjects at the time of SPT response conversion. Symptoms were not accompanied by a change in FEV(1) or bronchial responsiveness to histamine. Symptoms resolved after transferral, but occasional shortness of breath or wheeze persisted in 4 subjects. SPT reactions decreased or became negative in all workers after complete removal but remained unchanged in a craftsman with ongoing occasional exposure to contaminated materials. CONCLUSION: Although no randomized intervention was performed, this study proves the effectiveness of a medical surveillance program for the prevention of occupational asthma caused by platinum salts.

Exposure-effect relationship of platinum salt allergy in a catalyst production plant: conclusions from a 5-year prospective cohort study.

BACKGROUND: There is a high incidence of occupational asthma and rhinitis caused by platinum (Pt) salts in precious-metal refineries. OBJECTIVE: We sought to assess exposure to Pt salts and the incidence of Pt salt allergy in a catalyst production plant. METHODS: A 5-year prospective cohort study was performed in 159 catalyst production workers (94.6% of recruited), 50 craftsmen (92. 6% of recruited), and 66 control subjects (76.7% of recruited) at yearly intervals. Subjects were assigned to exposure categories of high levels of Pt (n = 115), persistently low levels of Pt (n = 51), intermittently low levels of Pt (n = 61), or no Pt (n = 48) after the initial survey according to job title and job location. Skin prick test conversion from a negative response to a 4 mm or larger wheal response with a 10(-2) mol/L hexachloroplatinic acid solution was chosen as the outcome variable. RESULTS: Exposure assessment of airborne Pt and Pt in the serum of workers demonstrated clear differences between exposure categories. The threshold limit value of 2 microg/m(3) for soluble Pt was exceeded in 3 (4%) of 78 measurements. Thirteen subjects assigned to high exposure showed skin test conversion, and new allergic symptoms were associated with exposure. Among the high-exposure category, the incidence rate of skin prick test conversion was 5.9 per 100 person-years for newly employed subjects (n = 79) and 2.1 per 100 person-years for those who had already been employed at the time of the initial survey (n = 36). A predicting factor for skin test conversion in highly exposed subjects was smoking status (relative risk, 3.9; 95% confidence interval, 1.6-9.7) but not atopy or bronchial hyperresponsiveness. CONCLUSION: Sensitization to Pt salts may develop in workers of catalyst production plants. Both the exposure to Pt salts and the incidence of Pt salt allergy were lower compared with reported data from precious-metal refineries.

A cross-sectional study of workers in the chemical industry with occupational exposure to hexamethylenetetramine.

OBJECTIVES: To assess the health effects of hexamethylenetetramine (HMT) on the airways and the skin of workers in the chemical industry. METHODS: A cross-sectional study was performed with 17 employees of a HMT-producing chemical plant and 16 control subjects from the plant. In addition, we examined 4 out of 5 subjects who had left the production for medical reasons during the last 10 years. Anamnestic data, total and specific IgE to four environmental allergens, lung function and bronchial responsiveness to methacholine were assessed by standard procedures. Skin prick tests (SPT) and patch tests were performed with known sensitizing substances and HMT 100 mg/ml and 2% pet and aq. RESULTS: A high number of exposed subjects and controls reported symptoms during the previous year (64.7% vs 68.8%), most of them were not related to work. Work-related symptoms and objective parameters did not show differences between groups. No sensitizations to HMT as assessed by SPT or patch tests were found. Among those who had left the HMT production for medical reasons, 2 former baggers showed sensitizations to HMT by patch tests. These reported eczema during exposure but lost symptoms after removal from exposure. Geometric mean HMT concentrations as assessed by personal sampling were 0.3 [95% confidence intervals (CI) 0.1; 0.9] mg/m(3) in shiftleaders and 0.6 (95% CI 0.3; 1.1) mg/m(3) in baggers. CONCLUSION: High exposures to HMT may cause allergic contact dermatitis. There was no evidence of an increased risk for occupational asthma at mean airborne HMT concentrations below 1 mg/m(3).

Outcome of occupational asthma due to platinum salts after transferral to low-exposure areas.

OBJECTIVE: To assess the health effects of transferral to low-exposure jobs on subjects with occupational asthma (OA). METHODS: We performed a cross-sectional survey of 83 workers in 2 platinum (Pt) refineries and 2 catalyst production plants, all with diagnosed OA due to Pt salts. In all, 9 workers (group A; 11%) continued to be exposed at the time of examination, 16 subjects (group B; 19%) had been transferred to other workplaces within the production building, 39 subjects (group C; 47%) had been transferred to areas outside the building but inside the plant, and 19 subjects (group D; 23%) had left the plant. The median period from transferral to examination was 54 months (lower quartile 23 months, upper quartile 84 months, n = 74). Symptoms, skin-prick tests (SPT) with environmental allergens and Pt salt, total serum IgE, lung function, and bronchial hyperresponsiveness were assessed by standard procedures. RESULTS: Asthma symptoms were reported by all subjects in the production area but by only 37 of 74 subjects (50%) after transferral, with no difference being found between groups B, C, and D. Both the proportion of subjects sensitized to Pt salts (100%, 88%, 67%, and 42% in groups A, B, C, and D, respectively) and the degree of sensitization were associated with exposure (P < 0.0002). Total IgE was higher in group A as compared with groups B, C, or D (P < 0.002). There was no association between bronchial hyperresponsiveness and exposure. Although no univariate difference in FEV1 was found between the groups, regression analysis showed an association between FEV1 and exposure (P < 0.002). In all, 13 subjects demonstrated a predicted FEV1 value of <80% (22%, 6%, 10%, and 32% in groups A, B, C, and D, respectively). They were older (median 49 versus 37 years; P < 0.002) and had worked over longer periods in high-exposure areas in spite of symptoms (median 43 versus 10 months; P < 0.003). Fifteen subjects of groups C or D had been removed from areas B previously, eight of them due to respiratory symptoms. CONCLUSIONS: For the majority of subjects with OA due to Pt salts transfer to low exposure areas as defined in this study may not be associated with a more unfavorable outcome as compared with complete removal from exposure sources.

A cross sectional study of chemical industry workers with occupational exposure to persulphates.

OBJECTIVES: Hair bleaches containing persulphates have been identified as the cause of occupational asthma in hairdressers. Also employees in persulphate production with occupational asthma have been described. It was the aim of this study to give an estimate of the prevalence of asthma due to persulphates in chemical workers with exposure to ammonium and sodium persulphate. METHODS: A cross sectional study was performed in 32 of 33 employees of a persulphate producing chemical plant. Eighteen of 23 workmen from the same plant with no exposure to persulphates were taken as controls. Also, information was collected from medical records of the seven subjects who had left the persulphate production for medical reasons since 1971. Data were recalled by a questionnaire, skin prick tests were performed with five environmental allergens, and ammonium and sodium persulphate (80 mg/ml). Specific immunoglobulin E (IgE) to the same environmental allergens as in the skin test, and total IgE were measured. Lung function and bronchial responsiveness to histamine were assessed by standard procedures. Workplace concentrations of ammonium and sodium persulphate were estimated by area and personal monitoring. The amount of persulphate was analysed as sulphur by inductively coupled plasma emission spectrometry. RESULTS: Work related rhinitis was reported by one subject with exposure to persulphates, conjunctivitis and bronchitis were reportedly related to work by two controls. There were no cutaneous reactions to persulphates in either group. Four non-atopic subjects exposed to persulphates, and two controls, one atopic and one non-atopic, were considered to be hyperresponsive to histamine. Three subjects exposed to persulphates with bronchial hyperresponsiveness (provocation dose of histamine causing a 15% fall in forced expiratory volume in one second (PD15 FEV1) < or = 1 mg) did not show variability in peak expiratory flow of > or = 20%, the rest refused peak flow measurements. None of the variables showed significant differences between the groups (P > 0.05). Six of the exworkers left because of work related contact dermatitis. Mean values for workplace concentrations of ammonium and sodium persulphate within the bagging plant were below 1 mg/m3, and the maximal concentrations were 1.4 mg/m3 and 3.6 mg/m3, respectively. CONCLUSION: Exposure to workplace concentrations of ammonium and sodium persulphate of about 1 mg/m3 in this chemical plant was not associated with a risk of occupational asthma.

Effects on the lung function of exposure to carbon black dusts. Results of a study carried out on 677 members of staff of the DEGUSSA factory in Kalscheuren/Germany.

Spirometry, full-bodyplethysmography, and inhalation challenge tests are the most frequently used methods for lung function testing. In all, 677 examinations were performed among exposed employees at the Degussa carbon black plant in Kalscheuren/Germany using the above mentioned methods, in order to detect whether there is a measurable impact of carbon black fine dust on pulmonary function, or a higher prevalence of obstructive air-way diseases among the study candidates, and whether fine dust exposure is related to the prevalence of bronchial hyperresposiveness. Within the smokers' group carbon black dust exposure reveals a (minimal) impact upon the lung function of the study subjects. However, the impact of fine dust exposure within that group is less significant than the influence of smoking on pulmonary function. Nevertheless, smokers are displaying significant more frequently signs of obstructive airway diseases compared with nonsmokers. In the smokers' group we found 7.3% of study subjects with signs of obstructive airway diseases compared with 3.9% in the group of nonsmokers. No significant impact of fine dust exposure on lung function could be detected within former- and nonsmokers. The overall percentage of 5.1% is not higher than that of subjects with bronchial hyperresponsiveness in other comparable studies.