Workers' compensation systems attempt to evaluate claims for occupational disease on an individual basis using the best guidelines available to them. This may be difficult when there is more than one risk factor associated with the outcome, such as asbestos and cigarette smoking, and the occupational exposures is not clearly responsible for the disease. Apportionment is an approach that involves an assessment of the relative contribution of work-related exposures to the risk of the disease or to the final impairment that arises for the disease. This article discusses the concept of apportionment and applies it to asbestos-associated disease. Lung cancer is not subject to a simple tradeoff between asbestos exposure and smoking because of the powerful biological interaction between the two exposures. Among nonsmokers, lung cancer is sufficiently rare that an association with asbestos can be assumed if exposure has occurred. Available data suggest that asbestos exposure almost invariably contributes to risk among smokers to the extent that a relationship to work can be presumed. Thus, comparisons of magnitude of risk between smokers and nonsmokers are irrelevant for this purpose. Indicators of sufficient exposure to cause lung cancer are useful for purposes of establishing eligibility and screening claims. These may include a chest film classified by the ILO system as 1/0 or greater (although 0/1 does not rule out an association) or a history of exposure roughly equal to or greater than 40 fibres/cm3•y. (In Germany, 25 fibres/cm3•y is used.) The mere presence of pleural plaques is not sufficient. Mesothelioma is almost always associated with asbestos exposure and the association should be considered presumed until proven otherwise in the individual case. These are situations in which only risk of a disease is apportioned because the impairment would be the same given the disease whatever the cause. Asbestosis, if the diagnosis is correct, is by definition an occupational disease unless there is some source of massive environmental exposure; it is always presumed to be work-related unless proven otherwise. Chronic obstructive airways disease (COAD) accompanies asbestosis but may also occur in the context of minimal parenchymal fibrosis and may contribute to accelerated loss of pulmonary function. In some patients, particularly those with smoking-induced emphysema, this may contribute significantly to functional impairment. An exposure history of 10 fibre•years is suggested as the minimum associated with a demonstrable effect on impairment, given available data. Equity issues associated with apportionment include the different criteria that must be applied to different disorders for apportionment to work, the management of future risk (eg. risk of lung cancer for those who have asbestosis), and the narrow range in which apportionment is really useful in asbestos-associated disorders. Apportionment, attractive as it may be as an approach to the adjudication of asbestos-related disease, is difficult to apply in practice. Even so, these models may serve as a general guide to the assessment of asbestosrelated disease outcomes for purposes of compensation.
Differences in vibration magnitude required for a human subject to differentiate wholebody vertical sinusoidal vibrations, difference thresholds for amplitude of sinusoidal vibration, have been determined at a vibration magnitude of 0.7 m/s2 r.m.s. at five octave band center frequencies from 4 to 63 Hz and at 80 Hz. The median difference thresholds of 16 male subjects seated on a flat rigid seat were found between 0.037 and 0.046 m/s2 r.m.s. at the frequencies used in this study. The subjects tended to be more sensitive to the change in vibration magnitude at 4 Hz than at 16, 31.5 and 63 Hz and less sensitive to the magnitude difference at 31.5 Hz than at 4, 8 and 80 Hz. The median relative difference thresholds, Weber's ratios, varied from 5.2% to 6.5% which were lower compared to the relative difference thresholds determined in the previous studies at frequencies where comparable data were available. The causes of the difference in the relative difference thresholds observed between this study and previous studies may include the difference in the psychophysical method used to determine the difference threshold.
Electromagnetic spectra reduce melatonin production and delay the nadirs of rectal temperature and heart rate. Seven healthy men (16-22 yrs) completed 4 permuted sessions. The control session consisted of a 24-hours bedrest at < 30 lux, 18°C, and < 50 dBA. In the experimental sessions, either light (1 500 lux), magnetic field (16.7 Hz, 0.2 mT), or infrared radiation (65°C) was applied from 5 pm to 1 am. Salivary melatonin level was determined hourly, rectal temperature and heart rate were continuously recorded. Melatonin synthesis was completely suppressed by light but resumed thereafter. The nadirs of rectal temperature and heart rate were delayed. The magnetic field had no effect. Infrared radiation elevated rectal temperature and heart rate. Only bright light affected the circadian rhythms of melatonin synthesis, rectal temperature, and heart rate, however, differently thus causing a dissociation, which might enhance the adverse effects of shiftwork in the long run.
Workplace protection factor (WPF) means a measure of the actual protection of respirator provided in the workplace when correctly worn. While fit factor (FF) represents a quantitative measure of the fit of a particular respirator to an individual and it is determined in the laboratory. To evaluate the relationship between WPF and FF is very important since FF may or may not be taken advantage of estimating WPF. Outside and inside Fe concentrations for three brand N95 filtering facepieces were collected on 14 workers/three respirator combinations in the welding workplace. The WPF measurements on the samples of the three respirator brands worn by 14 workers were observed to range from 2.2 to 132.9 with a geometric mean of 15.9 and a geometric standard deviation of 2.63. Respirator performances as measured by the WPF differed significantly among different respirator brands (p<0.05). In this study, correlations were found between the WPF measurements and the FF data for all samples of the three respirators (R2=0.38). The percentage of Fe particles having a smaller fraction than 1.1 μm diameter was observed as 71.6% of the total.
An epidemiological health study compared the health status of residents of a town exposed to an accidental Catacarb chemical release from an adjacent oil refinery, with the health status of demographically similar residents of an unexposed town in the region. Few studies of Catacarb's effects on humans exist; however, animal studies have shown it to be a respiratory, gastro-intestinal, dermatological and visual irritant. As part of the study, health questionnaires assessing pre- and post exposure symptoms, illnesses and medication use were mailed to residents in both towns. Medication use is sometimes reported to be a more objective and reliable measure of health outcomes1). The current paper compared medication use of exposed and unexposed residents. Significant increases after exposure were found in the use of the following medications: antacid, asthma medication, cough and cold medication, eye medication, headache medication and sleep medication. These increases were consistent with reported symptoms, albeit of greater magnitude; no increase in medication use for other illnesses was reported. Medication use in this sample was consistent with patients' report of symptoms and may be a better measure of outcome.
Carbofuran, a systemic N-methyl carbamate pesticide was orally administered with the doses of 0.4, 0.7, 1 and 1.3 mg/kg body weight/day to normal virgin female Swiss albino mice for 30 days. The vaginal smear and body weight of mice were recorded daily and mice were sacrificed on the 31st day. Estrous cycle was effected by showing a significant decrease in the number of estrous cycle and the duration of each phases of estrous cycle with concomitant significant increase in the diestrus phase in 1 and 1.3 mg/kg/d carbofuran treatment when compared with that of control mice. There was a significant decrease in the number of healthy follicles and a significant increase in the number of atretic follicles in 1 and 1.3 mg/kg/d treated groups when compared with the control. The histologic observations of the ovary revealed the presence of less number of healthy follicles and more number of atretic follicles in high dose of carbofuran treated mice. There was a dose dependent decrease in the body weight. The ovary weight was also decreased significantly in 1.3mg/kg/d carbofuran treatment. There were no significant change in the weight of the organs such as uterus, kidney, adrenal, liver, spleen, thymus and thyroid. These observed effects of carbofuran on the estrous cycle and follicles may be due to a direct effect on the ovary or the hypothalamo-hypophysial ovarian axis causing hormonal imbalance.
The purpose of this paper is to investigate the effects of posture, push force and rate of temperature change on thermotactile thresholds and to clarify suitable measuring conditions for Japanese people. Thermotactile (warm and cold) thresholds on the right middle finger were measured with an HVLab thermal aesthesiometer. Subjects were eight healthy male Japanese students. The effects of posture in measurement were examined in the posture of a straight hand and forearm placed on a support, the same posture without a support, and the fingers and hand flexed at the wrist with the elbow placed on a desk. The finger push force applied to the applicator of the thermal aesthesiometer was controlled at a 0.5, 1.0, 2.0 and 3.0 N. The applicator temperature was changed to 0.5, 1.0, 1.5, 2.0 and 2.5°C/s. After each measurement, subjects were asked about comfort under the measuring conditions. Three series of experiments were conducted on different days to evaluate repeatability. Repeated measures ANOVA showed that warm thresholds were affected by the push force and the rate of temperature change and that cold thresholds were influenced by posture and push force. The comfort assessment indicated that the measurement posture of a straight hand and forearm laid on a support was the most comfortable for the subjects. Relatively high repeatability was obtained under measurement conditions of a 1°C/s temperature change rate and a 0.5 N push force. Measurement posture, push force and rate of temperature change can affect the thermal threshold. Judging from the repeatability, a push force of 0.5 N and a temperature change of 1.0°C/s in the posture with the straight hand and forearm laid on a support are recommended for warm and cold threshold measurements.
Effects of low pH (6.0, 6.5) were studied at three temperatures (5, 15, 25°C) on the isometric force and stiffness of glycerinated muscle fibers dissected from soleus (type I) and psoas (type IIX) muscles of the Japanese white rabbit. It was observed that the maximum force and stiffness declined as pH decreased, the extent of which was diminished by an increase in temperature in both muscle types. The pH-induced changes in force were greater than those in the stiffness for both muscle types: at 5°C, the psoas showed greater change in stiffness than the soleus. As the pH of the contracting solution decreased, the time to peak stiffness decreased and the time to relaxation increased in both muscle types. At pH 6.0, the latter was significantly longer than the former. The force-stiffness curves indicated that, when pH decreased, force increased as fast as stiffness during contraction and force declined faster than stiffness during relaxation. The results suggested that one of the causes of muscle injury during hard muscular work could be the longer relaxation time in an acidic solution.
The hematopoietic toxicity of ethylene glycol monomethyl ether (EGME) and its metabolites, methoxy acetaldehyde (MALD) and methoxyacetic acid (MAA), was analyzed using human bone marrow cells from a lymphoma patient without bone marrow involvement and a human leukemia cell line, HL 60. After 24-hour incubation, the concentrations of 50 percent inhibition (IC50) of human hematopoietic progenitor cells with MALD or MAA were 3 mM and 3.9 mM, respectively, and EGME (10 mM or more) did not show any cytotoxicity. IC50 (after 48-hour exposure) of MALD and MAA on HL 60 cells were 2.45 mM and 5.6 mM, respectively, suggesting that both hematopoietic progenitor cells and HL60 have a similar sensitivity. DNA ladder formation, a characteristics of apoptosis, was observed in MALD- or MAA-treated HL60 cells, but not in EGME-treated samples. Caspase-3 enzyme activity, the effector of the apoptotic process, was greatly enhanced with MALD treatment. The inhibitor of caspase-3 repressed cell death induced with MALD as well as MAA.
Bisphenol A (BPA), a xenoestrogen, has been reported to mimic the actions of estrogen or to affect the endocrine glands in vivo and in vitro. In this study, we examined whether in utero and lactational exposure to BPA altered the somatic growth and anogenital distance (AGD) of F1 offspring (1, 3, and 9 weeks of age) in vivo in rats. Dams were orally administered with various doses of BPA (0, 4, or 40 mg/kg body weight (BW)/day) from gestation day (GD) 6 through postnatal day (PND) 20. There were no significant changes in body weight, liver weight, kidneys weight, testes weight, AGD, the ratio of AGD to BW, or the ratio of AGD to the cube root of BW in BPA exposed pups compared to the vehicle-exposed control. This suggests that prenatal and postnatal exposure (indirect exposure) to BPA (4-40 mg/kg/day, GD 6-PND 20) does not affect on somatic growth or AGD of F1 generation of male and female rats.
Five cases are reported in which malignant mesothelioma of the pleura and hepatocellular carcinoma co-existed in the same patient. The group included four men and one woman, aged between 58 and 86 years. The diagnosis was established at necropsy. In one case the association was clinically suspected. All mesotheliomas were asbestos-related. Liver cirrhosis co-existed in four cases, two of them positive for HCV markers. A lot of elements suggest that the above association is not a fortuitous coincidence. In particular, asbestos could favour liver cancerogenesis by inducing immune impairment.