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PubMed1978

[Proposal for threshold limit values for organic solvent concentrations in alveolar air].

The n-hexane concentration was determined in upper factory environmental air and in worker alveolar air. The relationship between the hexane alveolar concentration, and the hexane environmental concentration (Ca/Ci) was found to be steady during the 4,5 hours exposure and independent of the alveolar ventilation and hexane environmental concentration. These results suggest the hypothesis that alveolar TLV's can be fixed for hexane and other solvents.

Air Pollutants↗
PubMed1991

Lithium/aluminium alloys. A problem material for biological monitoring.

Investigations on aqueous and nonaqueous media have shown that the dust particles of lithium/aluminium alloy are readily soluble in blood serum. Concentration of 10 mg A1 and 3 mg Li in 1 l serum constitute the saturation values in human blood serum at 20 degrees C. Further observations are intended to clarify the danger at the workplace. With a short-term exposure, the change in concentration of Li and Al was followed in the working environment and in the staff. Both elements (Li and Al) were determined in the working air, in the urine, the blood serum and on human skin with electrothermal AAS. On human skin, microerosions arise owing to hydrolytic destruction of the epidermis after long-term contact. The intensive irritant action of Li/Al dust is most relevant for preventive measures. It must also be considered that the Al values in the blood serum are raised by up to 50% in the presence of Li. The resorption and/or the bioavailability of Al is altered by Li. In the presence of Li up to a Li content of 2.5% in Al dust, a MAK (biological tolerance value, threshold limit value) of 1 mg Al/m3 room air (for the total dust) is recommended.

Air Pollutants, Occupational↗
PubMed1990

[Threshold values for chemicals to prevent disease].

Proper interpretation of threshold limit values should always take into account that such limits are not absolute, but rather subject to change depending on advances in scientific knowledge. Threshold limit values derived from toxicologic study are best suited to evaluation of health risks of chemicals in the environment. Although more toxicologic information than is currently available would be desirable for the establishment of limit values, this should not prevent agreement on limits for more substances. "Better" threshold limit values would be forthcoming from epidemiologic studies, which are particularly rare in the FRG. Prospective studies measure current exposure; but appearance of detrimental health effects generally requires a lengthy latency period (e.g., decades in the case of cancer or cardiovascular disease). Threshold limit values permit monitoring and, if necessary, restriction of anthropogenic activity. Such restrictions are necessary, as shown by severe health damage which has occurred in the past (e.g., angiosarcoma due to vinyl chloride or neurogenic damage due to mercury in the workplace, tumors due to arsenic in drinking water, and methemoglobinemia in infants due to nitrite or renal damage due to cadmium in food). Evaluation of potential detrimental health effects for threshold limit values in environmental media is difficult because the effective dose cannot be determined. Monitoring of such limit values, which have already been incorporated into West German law, is relatively easy to implement, however (e.g. continuous outdoor air quality sampling and measurement, and periodic analysis of drinking water and foodstuffs). Since such monitoring may be performed close to the source, preventive measures should be easy to implement. Biological threshold limit values (biological monitoring) are essential to effective evaluation of the health effects of chemicals. Such limits should be established for more substances. When biological limit values are exceeded, however, it is generally difficult to determine the source(s) of exposure. Since individuals themselves cause the most damage to their own health e.g., through consumption of alcoholic beverages, cigarette smoking, or poor eating habits; the establishment of threshold limit values designed to protect individuals from themselves would be the most effective method of preventing environmental disease.

Air Pollution↗
PubMed1980

Dust in dental laboratories. Part I: Types and levels in specific operations.

The type and levels of dust in breathing air close to the workpiece produced through cutting, grinding, or polishing of alloys in dental laboratories have been characterized. The dust levels were compared with threshold limit values (TWA or STEL). In laboratories with improper local ventilation systems, dust levels considerably exceeding such values were recorded. Levels in excess of 10 times the threshold limit values were observed for solid mercury and silver present in amalgam dust, for cobalt present in nonprecious alloys, and for gypsum. Silver exceeded the threshold limit value 1,750 times in one case. Moderate excess of threshold limit values, that is less than 10 times, were measured for copper, nickel, tin, and porcelain in cases of insufficient ventilation. With the efficient outlet systems available on the commercial market, the dust levels could be reduced to levels consistent with criteria of threshold limit values except when trimming amalgam dies. Such systems comprise tubes with diameters of 35 mm connected to pumps with suction capacities of about 30 l/sec.

Air Pollutants↗
PubMed2001

A PBPK modeling-based approach to account for interactions in the health risk assessment of chemical mixtures.

The objectives of the present study were: (1) to develop a risk assessment methodology for chemical mixtures that accounts for pharmacokinetic interactions among components, and (2) to apply this methodology to assess the health risk associated with occupational inhalation exposure to airborne mixtures of dichloromethane, benzene, toluene, ethylbenzene, and m-xylene. The basis of the proposed risk assessment methodology relates to the characterization of the change in tissue dose metrics (e.g., area under the concentration-time curve for parent chemical in tissues [AUCtissue], maximal concentration of parent chemical or metabolite [Cmax], quantity metabolized over a period of time) in humans, during mixed exposures using PBPK models. For systemic toxicants, an interaction-based hazard index was calculated using data on tissue dose of mixture constituents. Initially, the AUCtarget tissue (AUCtt) corresponding to guideline values (e.g., threshold limit value [TLV]) of individual chemicals were obtained. Then, the AUCtt for each chemical during mixed exposure was obtained using a mixture PBPK model that accounted for the binary and higher order interactions occurring within the mixture. An interaction-based hazard index was then calculated for each toxic effect by summing the ratio of AUCtt obtained during mixed exposure (predefined mixture) and single exposure (TLV). For the carcinogenic constituents of the mixture, an interaction-based response additivity approach was applied. This method consisted of adding the cancer risk for each constituent, calculated as the product of q*tissue dose and AUCtt. The AUCtt during mixture exposures was obtained using an interaction-based PBPK model. The approaches developed in the present study permit, for the first time, the consideration of the impact of multichemical pharmacokinetic interactions at a quantitative level in mixture risk assessments.

Air Pollutants, Occupational↗
PubMed2005

Evaluation of employee exposure to organic tin compounds used as stabilizers at PVC processing facilities.

Organic tin compounds are primary substances used as heat stabilizers by the polyvinyl chloride (PVC) industry. The use of these compounds in the PVC industry is generally well controlled, usually by automated processes. This study was conducted to provide an overview of worker exposure to organic tin compounds at PVC processing facilities and to verify that these exposures are below the threshold limit value (TLV((R))) set by the American Conference of Governmental Industrial Hygienists for organic tin. The basis of the TLV indicates the principal concern is to minimize adverse effects on immune function and the central nervous system from airborne exposure to organic tin. The TLV has a skin designation based on the potential for percutaneous absorption; the TLVs for inhalation exposures are based on the presumption that there is no concurrent exposure via the skin and oral ingestion routes. Personal exposure monitoring was conducted following the National Institute for Occupational Safety and Health (NIOSH) 5504 sampling method and a modified version of the NIOSH analytical method. The results were reported as"total tin."The data indicated no average exposure levels for individual tasks exceeded the organic tin TLV, and 96%of results the samples were less than 20%of the TLV. Only 1 sample of 102 exceeded the TLV, and the individual was wearing appropriate respiratory protection. Subsequent investigation indicated the highest exposures occurred while the operators were conducting tasks that included manual handling of the organic tin compounds. These data suggest manual operations may have a greater potential for organic tin exposure.

Environmental Monitoring↗
PubMed1995

The limits of thresholds: silica and the politics of science, 1935 to 1990.

Since the 1930s threshold limit values have been presented as an objectively established measure of US industrial safety. However, there have been important questions raised regarding the adequacy of these thresholds for protecting workers from silicosis. This paper explores the historical debates over silica threshold limit values and the intense political negotiation that accompanied their establishment. In the 1930s and early 1940s, a coalition of business, public health, insurance, and political interests formed in response to a widely perceived "silicosis crisis." Part of the resulting program aimed at containing the crisis was the establishment of threshold limit values. Yet silicosis cases continued to be documented. By the 1960s these cases had become the basis for a number of revisions to the thresholds. In the 1970s, following a National Institute for Occupational Safety and Health recommendation to lower the threshold limit value for silica and to eliminate sand as an abrasive in blasting, industry fought attempts to make the existing values more stringent. This paper traces the process by which threshold limit values became part of a compromise between the health of workers and the economic interests of industry.

Health Personnel↗
PubMed1978

Mercury vapor levels in a dental laboratory.

Mercury vapor levels associated with grinding amalgam models and mulling amalgams in the palm of the hand following trituration have been measured in a dental laboratory in inhalation position. The threshold limit value of airborne mercury of 0.05 mg/m3 was essentially exceeded in the grinding procedure of amalgam. Levels in excess of seven times this value were recorded. During mulling the mercury vapor level fluctuated around the threshold limit value. The mean mercury concentrations did not essentially exceed the threshold limit value.

Air Pollutants↗
PubMed1991

[Efficiency of various dental dust-aspiration-equipment regarding the treatment of cobalt-chromium alloys].

The comparative measuring of the dust-seizure-efficiency of aspirators is being carried out by a practice-related treatment of 5 cylindrical-shaped specimen made of a commercial cobalt-chromium-alloy with aluminum-oxide-grinding instruments and silicone-rubber-polishers. A small-filter-apparatus takes up the person related samplings of the occurring total-dust-amount, which is then being calculated by a gravimetric standard-measuring-procedure. The cobalt-chromium-dust-fraction in the total dust amount is determined through an x-ray-fluorescence-analysis. Workplace dust-aspiration-equipment of the firms KaVo, Freuding and Wassermann have been subjected to testing. The values of the efficiency of all aspirators turned out to be below the American Threshold Limit Value TLV-TWA (Threshold Limit Value-Time Weighted Average) of 0.5 mg/m3 for chromium. The strict TLV-TWA-value of 0.05 mg/m3 for cobalt it also--with the exception of the Freuding-aspirator A 84 with aspiration-tube--not exceeded.

Air Pollutants, Occupational↗
PubMed2005

Scattered laser radiation and broadband actinic ultraviolet plasma emissions during LADARVision excimer refractive surgery.

PURPOSE: To evaluate the potential occupational health hazards associated with scattered actinic ultraviolet (UV) laser radiation and broadband actinic UV plasma emissions during refractive surgery. SETTING: Center for Refractive Surgery, Walter Reed Army Medical Center, Washington, D.C., USA. METHODS: Intraoperative radiometric measurements were made with the Ophir Power/Energy Meter (LaserStar Model with silicon detector, Model PD-10) and the International Light Radiometer/Photometer (Model IL 1400 with actinic ultraviolet detector, Model SEL240) with and without UV blocking filters (BLK 270 and Schott types WG-280 and WG-230). Measurements made during laser calibration as well as laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) procedures were evaluated using a worst-case scenario and then compared with the American Conference of Governmental Industrial Hygeinists (ACGIH) Threshold Value Limits (TLV) to perform a risk/hazard analysis. RESULTS: Most optical emissions were between 193 nm and 280 nm, and approximately 25% of the measurement result was due to broadband emissions greater than 270 nm for calibration targets. About 25% of optical emissions during LASIK were beyond 230 nm. No emissions beyond 230 nm were observed during PRK. Ultraviolet scattered radiation level was similar between PRK and LASIK. Maximum measured values of 80 nJ/pulse at 14 cm for PRK and 45 nJ/pulse at 38 cm for LASIK were used as the absolute worst-case analysis for exposure. Assuming the worst-case exposure conditions are equal to the maximum measured value during these studies at a workload of 20 patients per day, the cumulative occupational exposure at close range of actinic UV radiation did not exceed the 8-hour occupational exposure limit of 3 mJ/cm(2) for any 24-hour period. CONCLUSIONS: Scattered UV laser radiation did not exceed occupational exposure limits at distances greater than 30 cm from either laser calibration targets or patient treatments over a workday. Laser eye protection is not necessary to protect operating room personnel since exposure levels are very low even under a worst-case scenario.

Calibration↗