Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Maximum Allowable Concentration”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources
PubMed1991

The safety of low melting point bismuth/lead alloys: a review.

Low melting temperature bismuth alloys that contain about 20% to 25% lead and 10% cadmium are widely used in radiotherapy to construct shielding blocks. Since 1980, five papers have addressed questions concerning potential metal toxicity, safe shop practices, measurement of airborne vapors and metal particulates, and the results of biological testing of personnel fabricating secondary field shaping blocks. In February, 1990, the Occupational Safety and Health Administration (OSHA), proposed new occupational air concentration safety standards for cadmium and cadmium compounds. This review presents the potential toxicity of the components metals in low melting temperature bismuth lead alloys, reviews the proposed OSHA air concentrations standards, and describes proper practices of shop safety required to minimize the hazards of these metals and other potentially hazardous materials used in the block fabrication process. The review reveals that if proper practices are followed, fabrication of those blocks, including those containing cadmium, should not produce a shop environment that would produce metal toxicity in employees, and radiotherapy mold room personnel are unlikely to generate air concentrations of cadmium that exceed new proposed standards.

Alloys↗
PubMedDate not supplied

The correspondence between U.K. 'action levels' for lead in blood and in water.

This paper considers whether the Department of the Environment's water lead concentration criterion for lead pipe replacement and action in individual cases, i.e. 50 micrograms/l in any sample, is too high when set against the Department of Health's advisory action limit for blood lead concentration of 25 micrograms/100 ml. The relationships between blood lead and water lead concentrations found in the Glasgow and Ayr duplicate diet studies, together with unpublished data from Glasgow and Liverpool, indicate that over 10% of people exposed to an average water lead concentration of 100 micrograms/l (the earlier action level) would have blood lead concentrations above 25 micrograms/100 ml, as would about 4% of those exposed to 50 micrograms/l (the Maximum Admissible Concentration in an EEC Directive). For adults, average water lead concentrations should not exceed 30 micrograms/l to ensure compliance with the limit for blood lead, i.e. so that not more than 2% exceed 25 micrograms/100 ml. However, for one of the critical groups, bottle-fed infants (whose diet is 90% water), average water lead concentrations should not exceed 10-15 micrograms/l. The WHO's Provisional Tolerable Weekly Intake (PTWI) for children (25 micrograms/kg body weight) also implies that their water lead concentrations should not exceed 10-15 micrograms/l.

Humans↗
PubMed2003

[Chemical hazards induced by heavy metals refining processes].

BACKGROUND: Processes of refining heavy metals consist in removing impurities, which can be found in metals produced on industrial scale. People involved in heavy metals refining processes are primarily exposed to metals (Pb, Cd, Cu), metalloids (As, Se) and metal compounds. Exposure to dusts (from 2 to 50% SiO2) and sulfuric acid is an additional hazard. MATERIALS AND METHODS: The air concentrations of harmful chemical agents at heavy metals refining stations in two Polish Plants are presented. Several tens of workers employed in the processes of copper, lead, nickel sulfate, zinc, cadmium and silver production were examined. Concentrations of Cd, Ni, Se, Cu, Pb, Ag, As and Sb were determined by atomic absorption spectrometry (AAS) with a graphite tube, whereas Fe, ZnO oxide (as Zn), MgO (as Mg) and CaO (as Ca) by AAS with air-acetylene flame, and sulfuric acid by method described in PN-91/Z-04056/02. RESULTS: Lead concentrations in the samples collected in both Plants were often high (significantly exceeding Polish MAC values at some workstations). Arsenic concentrations ranged from very low in all processes in one Plant to very high, exceeding Polish MAC values, at some workstations in the other. In general, air concentrations of other agents were not high (fraction of MAC). The occurrence of antimony and magnesium oxide was not determined. CONCLUSIONS: The risk created by metals and metalloids at the workstations in two Plants was diversified. There is no need to determine Sb and MgO in further studies. Lead should be determined at all workstations, other agents can be determined at workstations with concentrations exceeding the determinability of relevant methods.

Air Pollutants, Occupational↗
PubMed1991

[Hygienic significance of surface-active substances in the conditions of soil contamination with chemical substances].

Urgent problems of the interaction of surface-active substances (SAS) with other ingredients under the conditions of chemical soil pollution are discussed, in particular, under the conditions of irrigation of agricultural fields with treated municipal sewage containing detergents. Before the beginning of the irrigation season the content of anion SAS in the arable layer of the soil is 2.02-2.66 mg/kg. In the middle of the vegetation period the quantity of detergents is increased 3-4 times fold. The authors suppose, that SAS may influence translocation of heavy metals from soil into plants. However, this question should be studied more carefully in the conditions of field experience with various SAS concentrations in soil.

Agriculture↗
PubMedDate not supplied

The evolution of standards for naturally occurring fluorides: an example of scientific due process.

In three quarters of a century of observation and research, the effects of fluoride on dental caries and on general bodily health have been well documented. An expanding data base has allowed a firming up of the guidance and standards for appropriate and safe levels of naturally occurring fluorides for human consumption. Over time, through specific recommendations, the maximum fluoride concentrations deemed appropriate have been altered, but by a process of considered adjustment. Although the Public Health Service has been responsible for the formalization of many of the recommended standards, those recommendations have been based on research from many fronts. In the most recent reconsideration of the standards for natural fluoride, the most exhaustive and thoroughly documented review to date was done, incorporating review by representatives from State, Federal, and private programs. Although the specific example of the development of standards for natural fluoride is used, it should be illustrative of similar processes that are constantly underway in regard to substances and factors with a potential impact on the public's health. Expansion of the data base through research and scientific inquiry will lay the foundation for future reconsideration of the standards for naturally occurring fluorides.

Dental Caries↗
PubMed1978

Epidemiological, dietary, toxicological and clinical nutrition studies on low-income population groups from a geographical area with endemic chronic arsenic poisoning.

An epidemiological, dietary, toxicological and clinical nutrition study, in an area with endemic chronic arsenic poisoning, was made. In a pilot study on 100 subjects from Antofagasta Commune, water dietary intake was associated with age (r = 0.678; P less than 0.000005). In a dietary survey (N = 220), performed to measure the mean and median arsenic doses, by age groups, there was a significant correlation amongst males (r = 0.800; P = 0.00956) and females (r = -0.791; P = 0.01121). A nutritional assessment of a male population sample (N = 100), of labourers and their children, showed a negative per cent change for food energy in 9 of the 10 age groups, with a maximum negative value of -47.4 (11--12 year-old group), when compared with U.S. recommended daily dietary allowances. For total protein intake, all age groups exhibited a negative per cent change, reaching a maximum value of -27.8 (7--10 year-old group). Since two boys with chronic arsenical dermatosis and prekwashiorkor were drinking water with a mean arsenic concentration of 0.08 and 0.06 ppm, respectively, a maximum permissible concentration of arsenic in drinking water of 0.01 ppm has been recommended as an international safety standard.

Adolescent↗
PubMed1996

[Hygienic aspects of the regulation of occupational chemicals].

Hygienic regulation of chemical hazards in the air of workplace has a 70-year history in this country. Now a definition "maximal allowable concentration in the air of workplace" needs to be more precise, and a list of MACs should be modified.

Hazardous Substances↗
PubMed1987

Urinary fluoride monitoring of industrial hydrofluoric acid exposure.

Preworkshift and postworkshift urinary fluoride concentrations were measured in 142 hydrofluoric acid (HF) workers and 82 unexposed workers aged 18 to 59. Postshift urinary fluoride concentration in HF workers was significantly higher than that in preshift or control workers. A linear relationship was observed between the mean values in urinary fluoride concentration and the HF concentration in the air. The mean urinary fluoride concentration of 4 ppm and its lower fiducial limit (95%, P = 0.05) of 2 ppm (specific gravity 1.024) were estimated corresponding to the atmospheric HF concentration of 3 ppm, which is the maximal allowable concentration recommended by the Japanese Association of Industrial Health and also the threshold limit value suggested by the American Conference of Governmental Industrial Hygienists. The results suggest that exposure to HF can be monitored by determining the urinary fluoride concentration.

Adolescent↗