Study On The Recommended Occupational Exposure Limits Of The Man-made Vitreous Fibre Insulation Wools

Man-made vitreous fibre insulation wools, include glass wool, rock wool and slag wool, denote groups of substances of non-crystalline, fibrous inorganic silicates, are widely used as asbestos substitutes for thermal and acoustical insulation, typically in buildings, vehicles and appliances. Man-made vitreous fibre insulation wools are new energy-saving materials, the rapid development, great production, widespread uses make them play an important role in promoting national economic development.Asbestos are confirmed carcinogens to humans, exposure to asbestos can lead to lung cancer, mesothelioma, and asbestosis, etc. Many countries have established laws to prohibit and restrict the manufacture and use of asbestos and its products. As asbestos substitutes, man-made vitreous fibre insulation wools have been widely used in industrial production and living, however, as similar to asbestos, they are also won highly attention for their health effects, especially the carcinogenicity. IARC once evaluated these substances and classified Group2B (possibly carcinogenic to humans) in1988, and reclassified these fibres from Group2B to Group3(cannot be classifiable as to its carcinogenicity-to humans) in2002. In addition, scientific literatures on other health effects are still limited, some effects are still controversial. To protect the health of laborers, many countries (areas) and organizations established their occupational exposure limits. Compared with only the total dust permissible concentration in China now, the number limit of fibre had been the main type of OELs for fibrous substances, and fibre counting method had been internationally accepted to measure the exposure levels for airborne asbestos and other fibres since1960s.To solve the above problems, we will systematically analyse the OELs of the man-made vitreous fibre insulation wools both at home and abroad, establish the determination method of airborne fibre number concentrations, evaluate the occupational exposure levels of different jobs, analyse the epidemiological characters of the heath effects, explore the dose-response relationship between the occupational exposure and the health effects, and recommend the occupational exposure limit values for man-made vitreous fibre insulation wools under the acceptable level of risk.Chapter1The health effects of man-made vitreous fibre insulation woolsObjectiveTo explore the carcinogenic and fibrosis effects induced by glass wool, rock wool and slag wool, analyse the different health outcomes induced by glass wool with the feature of low number concentration of fibre and low gravimetric concentration of total dust, and rock wool with low number concentration of fibre and high gravimetric concentration of total dust, explore the exposure (dose)-response relationship, provide the basis for selecting the key health effects of the OELs and suggesting the target diseases and effect indicators of the occupational health surveillance.MethodsRetrospectively collect the incidence data of pneumoconiosis, lung cancer, malignant mesothelioma and other tumors, and past medical examination data by questionnaires.When explore the relationship between the long-term exposure to man-made vitreous fibre insulation wools and the health effects on pulmonary function, respiratory symptoms, as well as nose and throat, the exposure group included workers continuously exposed greater than and equal to1year, excluded those who once exposed to asbestos and other fibers, and dust and chemical substances which can harm the respiratory system, suffering chronic bronchitis, emphysema and asthma, and in the last week suffered a cold. The control group were matched by the occupational hazards and working age, the exclusion criteria were same to the exposure group except the exposure to man-made vitreous fibre insulation wools. The exposure group was divided into three subgroups of (1～5a) group,(6～10a) group, and (>10a) group by exposure age.When explore the relationship between the exposure to man-made vitreous fibre insulation wools and the health effects on skin and eyes, the exposure group included workers in expose, the control group were matched by the occupational hazards and working age. the exposure group was divided into three subgroups by exposure level of total dust per week, low exposure group (<5mg/m3·week), medium exposure group (5-≤10mg/m3-week), and high exposure group (>10mg/m3-week), and also divided into two subgroups of (<la) group and (>1a) group.All subjects were investigated by interview questionnaire, including demographic information (gender, ethnicity, marital status, education background), occupational history, shifts, work content and work time, PPE, smoking, past medical history, family history, present illness, and symptoms of respiratory system, nasopharynx, skin and eyes. All iterms were filled in by the investigators who had accepted uniform training.According to Appendix B of Technical specifications for occupational health surveillance (GBZ188-2007), all subjects accepted pulmonary function test and common examinations for nasopharynx, skin and eyes. The main effects include restrictive dysfunction of pulmonary ventilatory, chronic rhinitis, chronic pharyngitis, irritant cantact dermatitis, conjunctivitis and keratitis.Statistical methods include ttest and analysis of variance, chi-square test and Logistic regression, Chi-square trend test, Wilcoxon rank-sum test, Kruskal-Wallis H test. Take a=0.1,(3=0.1as the cutoff value for stepwise method of Logistic regression, and take a=0.05as the cutoff value for the rest. Results5cases of Pneumoconiosis (Phase Ⅰ) were collected, of which2cases of mixed pneumoconiosis,1case of asbestosis, and2cases of’mineral wool pneumoconiosis’. All the’incidence’working ages were more than10years. No cases of lung cancer, malignant mesothelioma and other cancer were collected.Compared with the control group, the rock wool exposure group had significantly lower mean values of the FVC%and FEV1.0/FVC%(P<0.05). Three subgroups with different exposure age had no differences of the mean values of FVC%, FEV1.0%and FEV1.0/FVC%(P>0.05). The restrictive dysfunction of pulmonary ventilation was the main type, its detection rate was28.3%, it showed linear trend with the exposure age (P<0.05), no association with smoking (P>0.05), and no association with the interacion of smoking and rock wool (P>0.05). The proportion of the respiratory symptoms (wheezing, breathlessness, and chest colds and chest illness) of the rock wool exposure group were significantly higher than the the control group (P<0.05). The detection rate of the chronic rhinitis of the rock wool exposure group (7.1%) was not significantly higher than the the control group (2.8%)(P>0.05), and chronic pharyngitis of the rock wool exposure group (31.3%) was significantly higher than the the control group (5.7%)(P<0.05), chronic pharyngitis may be affected by rock wool and other factors such as smoking. The proportion of dry nose symptom and nasal congestion of the rock wool exposure group were significantly lower than the the control group(P<0.05).Compared with the control group, the glass wool exposure group had significantly higher mean values of the FVC%and FEV1.0%, and lower mean values of the FEV1.0/FVC%(P<0.05). Three subgroups with different exposure age had no differences of the mean values of FVC%and FEV1.0%(P>0.05),but FEV1.0/FVC%of (1-5a)group had significantly lower mean values than(6-10a)and (>10a) group (P<0.05). The detection rate of restrictive dysfunction of pulmonary ventilation was14.3%, it showed no association with glass wool,smoking, and the interacion of smoking and glass wool (P>0.05), no linear trend with the exposure age (P>0.05). The proportion of the respiratory symptoms (wheezing, breathlessness, and chest colds and chest illness) of the glass wool exposure group were significantly higher than the the control group (P<0.05). The detection rate of the chronic rhinitis of the glass wool exposure group (7.1%) was not significantly higher than the control group (2.8%)(P>0.05), and chronic pharyngitis of the rock wool exposure group (52.0%) was significantly higher than the the control group (5.8%)(P<0.05), chronic pharyngitis may be affected by glass wool and other factors such as smoking. The proportion of symptoms of dry nose, nasal congestion, Runny nose, sore throat of the glass wool exposure group were significantly higher than the control group(P<0.05).The detection rate of the irritant cantact dermatitis of the rock wool exposure group was10.1%, it showed linear trend with the current gravimetric concentration of total dust (P<0.05) but no association with the exposure age (P>0.05), and the detection rate of conjunctivitis of the exposed group (12.8%) was significantly higher than the control group (2.8%)(P<0.05). The proportion of shin and eye itching symptoms of the exposed group (54.1%and42.9%) were significantly higher than the control group (11.5%and26.5%)(P<0.05), but the differences among/between the exposed subgroups with different exposure level and different exposure age were not statistically significant (P>0.05).The detection rate of the irritant cantact dermatitis of the glass wool exposure group was6.7%, it showed no association with the current gravimetric concentration of total dust (P>0.05) and the exposure age (P>0.05), and the detection rate of conjunctivitis of the exposed group (5.0%) was not significantly higher than the control group (2.5%)(P>0.05).The proportion of shin and eye itching symptoms of the exposure group (38.6%and37.0%) were significantly higher than the control group (6.7%and21.8%)(P<0.05), the medium exposure group (60.5%and55.3%) were significantly higher than the low exposure group (28.4%and28.4%)(P<0.05), but the differences between the different exposure age subgroups were not statistically significant (P>0.05).ConclusionsLong-term exposure to rock wool and slag wool may induced certain negative effects on the respiratory system, can harm the pulmonary ventilation function, characterized by restrictive dysfunction of pulmonary ventilation, can cause respiratory symptoms, may also induced fibrosis.Long-term exposure to the rock wool with the feature of low number concentration of fibre and high gravimetric concentration of total dust can harm the pulmonary ventilation function, mainly restrictive dysfunction of pulmonary ventilation. However, long-term exposure to the glass wool with the feature of low number concentration of fibre and low gravimetric concentration of total dust did not significantly harm the pulmonary ventilation function. Higher accumulated concentration of rock wool total dust can induce more obvious effects of pulmonary function impairment than lower glass wool.Occupational exposure to man-made vitreous fibre insulation wools can cause the short-term, mechanical irritant effects such as shin and eye itching symptoms, irritant cantact dermatitis and conjunctivitis.The health outcomes of irritant cantact dermatitis and conjunctivitis induced by the rock wool with the feature of low number concentration of fibre and high gravimetric concentration of total dust were more significant than the glass wool with low number concentration of fibre and low gravimetric concentration of total dust. Higher concentration of rock wool total dust can induce more obvious mechanic irritant effects on the skin and eyes than lower glass wool.Therefore, effects of the respiratory system and mechanic irritant on the skin and eyes can be selected as the key health effects for establishing OELs. Except the fibrosis effect, the pulmonary ventilation dysfunction, irritant cantact dermatitis and conjunctivitis can be the target diseases, and respiratory symptoms, lung function tests, sikn and eyes examination, if necessary the nasopharynx check can be the effect indicators of the occupational health surveillance. The concentration of total dust should be critical control point for reduding the hazards of man-made vitreous fibre insulation wools.Chapter2Exposure assessment for the man-made vitreous fibre insulation woolsObjectiveTo establish the determination method for airborne fibre number concentrations of glass wool, rock wool and slag wool, explore the quantitative conversion relationship between the number concentration of fibre and gravimetric concentration of total dust, evaluate the exposure levels of different jobs.Methods2glass wool plants (A and B) and2rock wool (slag wool) plant (C and D) with better production continuity were selected as the study sites. Area sampling was used for the relatively static jobs and personal sampling for the itinerant jobs. Based on the determination method recommended by WHO, membrane of mixed esters of cellulose was used for sampling, and phase-contrast optical microscopy for observing the fiber size and counting the number. A countable fibre was any particle that has a diameter<3μm, length>5μm, and a length:diameter ratio>3:1. The weighing method were used to determine the gravimetric concentration of total dust of parallel samples. Correlation and regression analysis were used to explore the relationship between the number concentration of fibre and gravimetric concentration of total dust. According to the actual exposure time, estimate the exposure concentration per day (CTWA,8h) and per week (CTWA,40h) for different jobs.ResultsThe number concentrations of glass wool fibre(CTWA,8h and CTwA,40h) were all lower than1f/ml, and the gravimetric concentration of total dust were all lower than3mg/m3except packaging workers.The number concentrations of rock wool fibreCTWA,8h and CTWA,40h) were all lower than1f/ml, except board-turners. And almost all jobs from the production and deep processing line exposed to the gravimetric concentration of total rock wool dust exceeding3mg/m3.Both glass wool and rock wool parallel samples have the positively correlated relationship between the number concentration of fibre and gravimetric concentration of total dust (P<0.05). Linear regression, logarithmic curve, polynomial, power function and exponential curve model were fitted respectively for the two concentrations, all the coefficient of determination (R2) are low. The model with the top coefficient of determination was exponential curve model y=0.0051e0.5659x for glass wool, and power function model y=0.0146x1.0237for rock wool.ConclusionsThe determination method of airborne fibre number concentrations for man-made vitreous fibre insulation wools was established. For these fibres with large diameter, the number concentrations of fibre with diameter<3μm, length>5μm, aspect ratio>3:1were all lower, but the gravimetric concentration of total dust may still be higher.Both glass wool and rock wool have the positively correlated relationship between the number concentration of fibre and gravimetric concentration of total dust, but the two concentrations have no fixed regression relationship and no clear quantitative conversion relationship. The joint application of the two concentrations can more objectively reflect the actual exposure levels. The number concentration of fibre of all jobs from the glass wool plants and most from the rock wool plants were lower than1f/ml. The glass wool packaging workers and the rock wool operators from the production and deep processing line exposed to the gravimetric concentration of total dust exceeding3mg/m3.The glass wool plants generally showed the feature of low number concentration of fibre and low gravimetric concentration of total dust, the rock wool and slag wool plants generally showed the feature of low number concentration of fibre and high gravimetric concentration of total dust.Chapter3Comparative analysis on the occupational exposure limits of the man-made vitreous fibre insulation woolsObjective To compare and analyze the occupational exposure limits of the man-made vitreous fiber insulation wools both at home and abroad, provide the reference to recommend the occupational exposure limits to meet the needs of the technical and economic feasibility in China and coordinate with international standards.MethodsReview the research reports from the authoritative institutions, such as ILO, WHO, IARC, IPCS, etc. and the occupational exposure limits and their documentations. Conclude the items about the physical, chemical, and biologic properties, the key health effects, the number limits of fibres, and the gravimetric limits of dust.ResultsThe number limits of fibres were internationally accepted as the main OEL type for the man-made vitreous fiber insulation wools. Their values ranged form0.5to3 f/ml, most were lf/ml. Some countries or organizations also established the gravimetric limits of dust as important supplement. The key health effects were the mechanical irritant effects to the skin and mucous membranes.A countable fibre, as defined by WHO, is any particle that has a diameter<3μm, length>5μm, and a length:diameter ratio>3:1, as defined by NIOSH ’A’ rules, is any particle that has a length>5μm, and a length:diameter ratio≥3:1, as defined by NIOSH’B’ rules, is any particle that has a diameter<3μm, length>5μm, and a length:diameter ratio≥3:1.ConclusionsThe number limits of fibre were the main OEL type, however, China only established the gravimetric limits of total dust and the values (3mg/m3) were relatively rigider than most countries. So we should supplement the the number limits of fibre to coordinate with the international standards, and pay attention to the theoretical and practical significance of the gravimetric limits of total dust, further explore its reasonable values. Despite of their differences of the physical, chemical, and biologic properties, glass wool, rock wool, and slag wool have the same values of the occupational exposure limits within a standard.Chapter4Study on the recommended occupational exposure limits of the man-made vitreous fibre insulation woolsLong-term exposure to rock wool and slag wool may induced certain negative effects on the respiratory system, can cause the short-term, mechanical irritant effects on the shin and eyes. So the respiratory effects, mechanical irritant effects on the shin and conjunctiva were the key effects for the OELs.On the OEL’s type, the gravimetric limits of total dust were recommended as the main OEL type because the hazards of large diameter fibers of the man-made vitreous fibre insulation wools are mainly mechanical irritant to the skin and conjunctiva. According to the general practice of most countries and the respiratory system effects induced by long-term exposure, the number limits of fibre were recommended as supplementary OELs. The joint application of the two concentrations was recommended to evaluate the occupational exposure levels.On the OEL’s values, as the gravimetric concentrations of total dust in many plants are still exceeding3mg/m3and the OELs of most countries are not rigider than ours, the gravimetric limits of total dust are recommended to adjust from3mg/m3to5mg/m3. The reduction of gravimetric concentration of total dust are recommended as critical control point. As the the number concentrations of fibre of most jobs had been controlled under1f/ml and the number limits of fibre of most countries were1f/ml, the value of1f/ml can be equivalently adopted.According to the results of this study, except the fibrosis effect, the pulmonary ventilation dysfunction, irritant cantact dermatitis and conjunctivitis are recommended as the target diseases, and respiratory symptoms, lung function tests, sikn and eyes examination, if necessary the nasopharynx check as the effect indicators of the occupational health surveillance.