Survey of construction workers repeatedly exposed to chlorine over a three to six month period in a pulpmill: I. Exposure and symptomatology.

OBJECTIVE: The admission to hospital of three construction workers with acute respiratory distress caused by inhalation of chlorine gas prompted the inspection of a building site located in a kraft pulpmill. The accidental emissions had taken place in the bleach plant and the construction workers assigned there were surveyed to uncover possible large scale health effects. DESIGN AND PARTICIPANTS: A questionnaire was presented to 281 workers (participation rate = 97%); 257 workers reported an average of 24 exposure episodes to chlorine and derivatives over a three to six month period. The air monitoring data available from the pulpmill's industrial hygienist were not useful in linking specific events reported by the workers to environmental conditions in the bleach plant. RESULTS: Over 60% of the workers described a characteristic flu like syndrome that lasted for an average of 11 days and was exacerbated by new bouts of exposure. Irritation of the throat (78%) and eyes (77%), cough (67%), and headache (63%) were the most often reported symptoms. Shortness of breath was reported by 54% of the participants and was not associated with age, smoking state, or history of asthma or chronic bronchitis. First aid self referral was associated with significantly greater reporting of most symptoms, including dyspnoea and cough. A significantly greater proportion of workers in the dyspnoea group had gone at least once for first aid care after a gassing incident (64% as opposed to 48%, p = 0.008). Throat irritation and cough persisted for mean intervals of eight and 11 days respectively. A flu like syndrome lasted for an average of 20 days. Seventy one subjects were considered to be a moderate to high risk of having persisting respiratory symptoms. CONCLUSION: Throat and eye irritation as well as cough and flu like symptoms are frequent occurrences after repeated accidental inhalation of chlorine. Subjects who consulted first aid care stations after a gassing incident are more likely to have persisting dyspnoea.

Survey of construction workers repeatedly exposed to chlorine over a three to six month period in a pulpmill: II. Follow up of affected workers by questionnaire, spirometry, and assessment of bronchial responsiveness 18 to 24 months after exposure ended.

OBJECTIVE: The aim was to determine the prevalence of persistent respiratory symptoms and bronchial hyper-responsiveness due to reactive airways dysfunction syndrome in a population of construction workers at moderate to high risk of developing the syndrome, at an interval of 18 to 24 months after multiple exposures to chlorine gas during renovations to a pulp and paper mill. DESIGN AND PARTICIPANTS: 71 of 289 exposed workers (25%) were identified on the basis of an exposure and the onset of respiratory symptoms shortly after this event (moderate to high risk). A standardised respiratory questionnaire was first presented, followed by spirometry and a methacholine inhalation test on those whose questionnaire suggested the persistence of respiratory symptoms. RESULTS: 64 of 71 (90%) subjects completed the respiratory questionnaire at the time of the follow up. The questionnaire suggested a persistence of respiratory symptoms in 58 of the 64 workers (91%). Of the 58 subjects, 51 underwent spirometry and assessment of bronchial responsiveness. All of them used bronchodilators as required (not regularly) and four required inhaled anti-inflammatory preparations. Sixteen had bronchial obstruction (forced expiratory volume in one second) (FEV1 < 80% predicted) and 29 showed significant bronchial hyper-responsiveness. CONCLUSION: Of the subjects (n = 71) who were at moderate to high risk of developing reactive airways dysfunction syndrome after being exposed to chlorine and were seen 18 to 24 months after exposure ended, 58 (82%) still had respiratory symptoms, 16 (23%) had evidence of bronchial obstruction, and 29 (41%) had bronchial hyper-responsiveness.

Cytogenetic effects of low-level exposure to toluene, xylene, and their mixture on human blood lymphocytes.

The present study was undertaken to investigate, both in vitro and in vivo, the genotoxic potential of short-term low-level exposure to toluene, xylene, and their mixture, for which information is limited at the present time. Five adult healthy white men were exposed for 7 consecutive hours per day over 3 consecutive days to 50 ppm toluene and 40 ppm xylene either alone or in combination in a controlled exposure chamber. Such an exposure was repeated three times at intervals of 2 weeks. Blood samples were taken before and after the termination of such exposure. Three different cytogenetic end-points were evaluated using peripheral blood lymphocytes: number of sister chromatid exchanges (SCEs), cell cycle delay, and cell mortality. No significant effects on SCEs, cell cycle delay, and cell mortality were observed following such exposure to toluene or xylene or their mixture. Similarly, exposure of human blood lymphocytes in vitro to either toluene (0-2.5 mM) or xylene (0-2 mM) or their mixture for 72 h did not result in any significant cytogenetic effects at lower concentrations, while at higher concentrations, only cell mortality was found to be significantly affected. Thus our present study indicates that simultaneous exposure to low levels (within the admissible limits) of toluene, xylene, or their mixture for a short period does not pose any potential mutagenic threat to humans.

Dose-dependent genotoxic effects of styrene on human blood lymphocytes and the relationship to its oxidative and metabolic effects.

Although the genotoxic potential of styrene is known, very limited information is available regarding its dose-dependent genotoxic response to human blood lymphocytes and how such response correlates with different metabolic events in whole blood lymphocytes. The present study was therefore carried out to study such a relationship using in vitro human blood lymphocytes from healthy volunteers. To study genotoxic response to styrene, sister chromatid exchanges (SCEs), cell cycle, and cell survival were analyzed. Lymphocytes were cultured for 72 hr in the presence of different concentrations of styrene (0-1,000 microM). Twenty-four hr before harvest, BrdU (5 micrograms/ml) was added to assess the increase in SCEs and cell cycle delay. Both the SCE frequency and the cell cycle length were increased linearly with increasing concentrations of styrene up to 200 microM, without addition of any exogenous metabolizing system. Above 200 microM, no further increase in genotoxic response occurred. The range of concentrations (10-200 microM) at which increase of cell cycle length due to styrene was observed did not impair the viability of the cells, suggesting that such cell cycle delay is a genotoxic-related event and not caused by cytotoxicity. In vitro metabolic transformation of styrene in whole-blood lymphocyte cultures without the presence of any exogenous metabolic activation system showed the formation of a reactive intermediate, styrene 7,8-oxide, to be capacity-limited, as verified from a nonlinear increase in the formation of styrene glycol. The value of such metabolic parameter reached a plateau above 200 microM styrene. The same phenomenon of saturation has also been observed with regard to other metabolic effects due to styrene in whole blood lymphocytes in culture, such as dose-dependent increase in lipid peroxidation and depletion of blood lymphocyte glutathione. Based on the relationship between the formation of different metabolic events and the genotoxicity of styrene, it may be possible that the genotoxic properties of styrene in human blood lymphocytes may be mediated initially not only by the formation of the presumably reactive styrene 7,8-oxide, but also by that of a reactive oxygen species as well. However, the present data are not sufficient enough to definitely identify the role of reactive oxygen species in such toxicity and therefore it warrants further study.

The increased susceptibility of women to multiple sclerosis.

Many diseases with an auto-immune etiology have a skewed sex distribution. In the majority of instances, women are affected more frequently than men. A review of population studies demonstrates that the preponderance of women in multiple sclerosis (MS) is almost constant. We show that this preponderance is further increased in early as well as in late-onset cases, in familial cases as well as in MS twin pairs and that the HLA-DR2 allele, which has been associated with MS in Caucasian populations, is significantly more frequent in women than in men with MS. "Rules" have been established for multifactorial diseases; MS contravenes most of those rules. The skewed sex distribution in MS could be attributed to the known hormonal and gender influences on the immune response, as well as to genetic influences.

Crossover site selection during recombination of polyomavirus replicons.

Two hybrid replicons containing polyomavirus (Py) genomes with large duplications of the viral late coding sequences were transfected into various permissive mouse cell lines. In all cell lines, either replicon yielded the sole amplifiable product expected from intramolecular homologous recombination, unit-length Py DNA (P155). In normal and in Py-transformed cells, such recombination was highly effective and involved sequences previously found to act as recombination hot spots (S repeats). In cells transformed by simian virus 40, however, these hot spots were inoperative in the generation of P155, which occurred with a reduced efficiency. These data confirm and extend earlier data indicating that the nature of products arising from recombination in Py replicons is tightly controlled by both cis- and trans-acting factors.

Analysis of low concentrations of 5-bromo-2-deoxyuridine on sister chromatid exchanges in human lymphocytes.

To determine a concentration of 5-bromo-2-deoxyuridine (BrdU) sufficient for sister chromatid differentiation (SCD), and yet having a minimal effect on the number of sister chromatid exchanges (SCEs), we assessed the effect produced on the number of SCEs by low concentrations (1, 3, and 10 micrograms/mL) of BrdU. SCD was not obtained in 19% of the 31 subjects with 1 microgram/mL of BrdU, while the differentiation was adequate for all samples treated with 3 and 10 micrograms/mL. We statistically analysed the effects of these three different doses and found no significant difference in the number of SCEs obtained with the doses of 1 and 3 micrograms/mL, but a significant difference was observed between these two concentrations and 10 micrograms/mL. We therefore suggest that the dose of 3 micrograms/mL, while sufficient to produce reliable differential staining, still permits an adequate evaluation of the base line of SCEs and appears to enhance the sensitivity of the test to evaluate between-individual variations. Our experiments also underline that SCE counts should include the centromere exchanges.

Analysis of sister-chromatid exchanges (SCEs) in familial and sporadic multiple sclerosis.

The levels of sister-chromatid exchanges (SCEs) were calculated in 17 multiple sclerosis (MS) patients (14 familial and 3 sporadic cases) and 16 healthy controls matched for sex and age. The SCEs were significantly increased for MS patients (p = 0.0002), while there was no statistically significant difference between men and women and between younger and older subjects in both groups. Such factors as familial occurrence and severity of MS, smoking habits, and distribution of lymphocyte subpopulations were discussed. Although there was a significant difference between the MS patients taking medication and the patients taking none (p = 0.038), the latter were still significantly different from the controls (p = 0.035), supporting the fact that the disease itself increases SCEs. Our study, done with 2 doses of BrdU, also shows that the increased SCEs in MS patients are not due to a hypersensitivity to this substance known to be an inducer of SCEs. Thus we suggest that the increased SCEs found are probably disease-related.

Inhibition of the immune response to whooping cough and tetanus vaccines by malaria infection, and the effect of pertussis adjuvant.

Plasmodium yoelii infection of mice depressed their capacity to build up humoral immune response to diphteria vaccine and protective immunity against tetanus toxin. This immunodepression was overcome by Freund's complete adjuvant or killed pertussis bacilli (whooping cough vaccine). These results suggest that vaccines should be given in association in malaria endemic area.

Isolation and characterization of phenotypes of mycobacteria.

Several strains of mycobacteria grown as surface pellicle on liquid Sauton's medium under semianaerobic conditions dissociated into three phenotypes: phenotypes 1, 2, and 3. Only phenotype 1 could be obtained in a pure state. None of these phenotypes was found to be stable: they convert from one into another and all revert to the parental strain when replaced in their usual aerobic cultural conditions. Comparative studies of phenotypes 1 and 3 have shown that significant differences exist in their physiological behaviour and antigenic composition.

Statistical tables to detect significance between frequencies in two small samples, with particular reference to biological assays.

By simply referring to one of three tables, derived from Fisher's exact factorial method and obtained with the aid of a computer, it is possible to decide readily if differences observed between two small and equal or unequal size series are statistically significant at probability levels of 0.10, 0.05 and 0.01. The same can be very helpful for planning experiments. Examples are given in various fields of biology.

Asparaginase activity of BCG and its phenotypes in relation to culture phases.

The asparaginase activity of the Montreal strain of BCG and of 2 of its phenotypes varies with the age of the culture; it starts to increase at the midlog phase of growth, reaches a maximum value near the end of this phase and decreases during the stationary or autolytic phase. However, the variations in this enzyme activity are greater in 2 the phenotypes than in the parental BCG.

Inhibition of the immune response to pertussis vaccine during Plasmodium berghei yoelii infection in mice.

Mice infected with Plasmodium berghei yoelii responded poorly to pertussis vaccine when administered at peak parasitemia. This was shown by serum agglutinin titers and lack of protection against intracerebral challenge with virulent Bordetella pertussis.

Microtissue culture test for the titration of low concentrations of diphtheria antitoxin in minimal amounts of human sera.

A microtissue culture method for the assay of low concentrations of diphtheria antitoxin in human sera has been developed, using a monkey kidney cell (VERO) culture technique. Results obtained with sera from nonvaccinated children and with immune sera from children vaccinated with three and four injections of diphtheria pertussis tetanus vaccine were in agreement with antitoxin levels considered necessary to denote immunity to diphtheria. The use of microplates and organic buffer for culturing the animal cells improved the stability of the tissue culture system. The described method is sensitive, economical, and applicable for the titration of antitoxin in human sera particularly from infants and children from whom a minimum amount of serum is available.