Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Threshold Limit Values”

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 19 recordsLinked to original sources
PubMed1990

But they are not thresholds: a critical analysis of the documentation of Threshold Limit Values.

Threshold Limit Values (TLVs) represent conditions under which the TLV Committee of the American Conference of Governmental Industrial Hygienists (ACGIH) believes that nearly all workers may be repeatedly exposed without adverse effect. A detailed research was made of the references in the 1976 Documentation to data on "industrial experience" and "experimental human studies." The references, sorted for those including both the incidence of adverse effects and the corresponding exposure, yielded 158 paired sets of data. Upon analysis it was found that, where the exposure was at or below the TLV, only a minority of studies showed no adverse effects (11 instances) and the remainder indicated that up to 100% of those exposed had been affected (8 instances of 100%). Although, the TLVs were poorly correlated with the incidence of adverse effects, a surprisingly strong correlation was found between the TLVs and the exposures reported in the corresponding studies cited in the Documentation. Upon repeating the search of references to human experience, at or below the TLVs, listed in the more recent, 1986 edition of the Documentation, a very similar picture has emerged from the 72 sets of clear data which were found. Again, only a minority of studies showed no adverse effects and TLVs were poorly correlated with the incidence of adverse effect and well correlated with the measured exposure. Finally, a careful analysis revealed that authors' conclusions in the references (cited in the 1976 Documentation) regarding exposure-response relationships at or below the TLVs were generally found to be at odds with the conclusions of the TLV Committee. These findings suggest that those TLVs which are justified on the basis of "industrial experience" are not based purely upon health considerations. Rather, those TLVs appear to reflect the levels of exposure which were perceived at the time to be achievable in industry. Thus, ACGIH TLVs may represent guides of levels which have been achieved, but they are certainly not thresholds.

Air Pollutants, Occupational↗
PubMed2005

A non-parametric framework for estimating threshold limit values.

BACKGROUND: To estimate a threshold limit value for a compound known to have harmful health effects, an 'elbow' threshold model is usually applied. We are interested on non-parametric flexible alternatives. METHODS: We describe how a step function model fitted by isotonic regression can be used to estimate threshold limit values. This method returns a set of candidate locations, and we discuss two algorithms to select the threshold among them: the reduced isotonic regression and an algorithm considering the closed family of hypotheses. We assess the performance of these two alternative approaches under different scenarios in a simulation study. We illustrate the framework by analysing the data from a study conducted by the German Research Foundation aiming to set a threshold limit value in the exposure to total dust at workplace, as a causal agent for developing chronic bronchitis. RESULTS: In the paper we demonstrate the use and the properties of the proposed methodology along with the results from an application. The method appears to detect the threshold with satisfactory success. However, its performance can be compromised by the low power to reject the constant risk assumption when the true dose-response relationship is weak. CONCLUSION: The estimation of thresholds based on isotonic framework is conceptually simple and sufficiently powerful. Given that in threshold value estimation context there is not a gold standard method, the proposed model provides a useful non-parametric alternative to the standard approaches and can corroborate or challenge their findings.

Air Pollutants, Occupational↗
PubMed2003

I are we closer to developing threshold limit values for allergens in the workplace?

OBJECTIVE: To define threshold limit values and legally binding occupational exposure limits. DATA SOURCES: Review of suitable literature. STUDY SELECTION: Studies based on detailed descriptions and/or measurements of airborne allergenic dust, total allergens, or even key allergens were selected. RESULTS: Prevalences of IgE-mediated sensitization and occupational asthma are related to the aeroallergen load in workplaces. Data to set threshold limit values for flour, latex, a-amylase, and isocyanates are already sufficiently available. CONCLUSIONS: To optimize primary prevention in workplaces,health-based occupational exposure limits should be set for major occupational allergens.

Allergens↗
PubMed2003

Estimation of the general threshold limit values for dust.

In 1997 the German MAK Commission set new general threshold limit values for dust. The procedure has recently been assessed (McLaughlin et al. 2001). One of the points raised was the use of inappropriate statistical methods. We want to address this point to a greater extent by discussing several alternatives implied by the already established threshold models, and we present results from a new approach that has been refined in the meantime: the use of the additive isotonic model. The underlined assumption of monotonicity regarding the dose-response relationship has been extensively investigated. One very flexible model, based on smoothing splines, shows in some of the samples a decline in the risk over a certain range of the exposure compared to the risk at baseline. Another approach with fractional polynomials and segmented regression lines shows that this result can be explained by chance. These methods show an increasing risk with increasing exposure. Additionally, permutation tests are used to prove the trend within the isotonic framework. The results from the additive isotonic model confirm previous assessments of the general threshold limit value.

Dose-Response Relationship, Drug↗
PubMed1986

Identification and classification of carcinogens: procedures of the Chemical Substances Threshold Limit Value Committee, ACGIH. American Conference of Governmental Industrial Hygienists.

The Chemical Substances Threshold Limit Value Committee of the American Conference of Governmental Industrial Hygienists has refined its procedures for evaluating carcinogens. Types of epidemiologic and toxicologic evidence used are reviewed and a discussion is presented on how the Committee evaluates data on carcinogenicity. Although it has not been conclusively determined whether biological thresholds exist for all types of carcinogens, the Committee will continue to develop guidelines for permissible exposures to carcinogens. The Committee will continue to use the safety factor approach to setting Threshold Limit Values for carcinogens, despite its shortcomings. A compilation has been developed for lists of substances considered to be carcinogenic by several scientific groups. The Committee will use this information to help to identify and classify carcinogens for its evaluation.

Carcinogens↗
PubMed1988

Corporate influence on threshold limit values.

Investigations into the historical development of specific Threshold Limit Values (TLVs) for many substances have revealed serious shortcomings in the process followed by the American Conference of Governmental Industrial Hygienists. Unpublished corporate communications were important in developing TLVs for 104 substances; for 15 of these, the TLV documentation was based solely on such information. Efforts to obtain written copies of this unpublished material were mostly unsuccessful. Case studies on the TLV Committee's handling of lead and seven carcinogens illustrate various aspects of corporate influence and interaction with the committee. Corporate representatives listed officially as "consultants" since 1970 were given primary responsibility for developing TLVs on proprietary chemicals of the companies that employed them (Dow, DuPont). It is concluded that an ongoing international effort is needed to develop scientifically based guidelines to replace the TLVs in a climate of openness and without manipulation by vested interests.

Acrylonitrile↗
PubMed1990

[UV exposure in the workplace. Apropos the establishing of threshold limit values].

Although UV exposure is present at many workplaces, it has not gained much attention. Particularly with regard to UVA, the UV threshold limit values for acute effects used to date are insufficient, and there are no obligatory limits to prevent the sequels of chronic UV exposure. More precise threshold limit values have been published only preliminarily (DIN-Standard No. 5031, part 10). There is a need for regulations governing the supervision of occupational UV exposure and the individual protection of exposed persons.

Dose-Response Relationship, Radiation↗
PubMed2001

A critical evaluation of the scientific basis of the MAK Commission's new general threshold limit values for dust.

In 1997, the German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area set a new MAK value ("Maximale Arbeitsplatz-Konzentration") governing worker exposures to general airborne dust. The new values limit worker dust exposures to concentrations not exceeding 1.5 mg/m3 for respirable dust and 4 mg/m3 for inhalable dust, and are substantially lower than corresponding standards in other western industrialized nations. The purpose of this document is to critically review the science behind the MAK Commission's new threshold limit value standards. The Commission relied heavily upon a re-analysis of data from the Deutsche Forschungsgemeinschaft (DFG) Chronic Bronchitis study (1965-1977). We have reservations about the scientific merit of the DFG study and the validity of data used as the basis for establishing a new MAK value for dust. In particular: (1) Assessing the potential role of inert dust in the development of chronic bronchitis in worker cohorts with extremely high cigarette smoking prevalences is scientifically implausible. (2) It is unlikely that the dust in the industries studied, including steel works, foundries and cement works, was in fact "inert", and any effects of the dust on chronic bronchitis rates may have been increased by the presence of free crystalline silica and other toxic agents. (3) The study made use of area- rather than personal-exposure monitoring, thereby correlating the prevalence of chronic bronchitis with lower dust exposure levels than actually existed and significantly overstating the health effects of the dust exposures. (4) Inappropriate statistical methods were used to estimate threshold limit values. Results of three additional epidemiological studies are cited as providing evidence of chronic lung effects due to insoluble dust exposure. All three studies suffer from extremely poor documentation of the study methodology, particularly regarding lung function testing, and they provide little evidence that exposure to insoluble non-fibrogenic dusts leads to chronic lung obstruction. In summary, it is our opinion that the studies evaluated by the MAK Commission and the methods used do not provide the scientific basis to support the lower threshold limit values for dust. We recommend that an appropriate prospective morbidity study be conducted to address the concerns detailed in this critical examination.

Bronchitis↗
PubMed1984

The origin and basis of threshold limit values.

The concept of establishing a "threshold limit" for contaminants of industrial air is based on the principles of establishing: (1) quantitative relationships between the magnitude and duration of exposure to an industrial substance and the nature and magnitude of the response of the worker, and (2) a limiting level of exposure to potentially hazardous agents, when there exists no significant threat to health. This paper focuses on the origin of this concept, and traces the history and development of thought concerning the founding principles upon which it is based. The TLVs have undergone a remarkable evolution, from values denoting concentrations of contaminant producing overt signs of acute toxicity, to those concentrations to which nearly all workers may be exposed for their working lifetime without experiencing adverse health effects.

Environmental Exposure↗
PubMed1992

The role of threshold limit values in U.S. air pollution policy.

This paper analyzes the role of threshold limit values (TLVs) in national air pollution policy during the 1980s, a period in which the Environmental Protection Agency (EPA) sought to delegate to individual states the authority to evaluate and regulate airborne toxic substances. We focus on 20 carcinogens and 11 substances with non-genotoxic health effects that were regulated by local air toxics programs using TLVs. Data from EPA's National Air Toxics Information Clearinghouse indicate that maximum TLV-based Ambient Air Level guidelines (AALs) frequently exceed minimum TLV-based AALs by a factor of greater than 1,000. Cancer potency data from EPA's Integrated Risk Information System suggest significant risks remain at TLV-based AALs. Cancer risks at the median TLV-based AAL exceed 1,000 cases per million exposed persons for cadmium (1,040), nickel and its compounds (1,420), propylene oxide (1,550), coke oven emissions (1,860), benzene (2,500), arsenic and its compounds (7,300), N-nitrosodimethylamine (21,000), asbestos (21,500), and ethylene dibromide (55,000). We also summarize published studies that report non-genotoxic health effects in workers exposed at levels near the TLV for 11 substances whose AALs were based on TLVs. Contrary to the assumption frequently made by state air toxics program, TLVs cannot be taken to represent no observed effect levels (NOELs) for regulatory purposes.

Acrylonitrile↗
PubMedDate not supplied

An analysis of the implications of a magnetic field threshold limit value on utility work practices.

This article examines the implications of a 10 gauss (G) occupational threshold limit value (TLV) on the work practices of a utility that must maintain and repair 500 and 230 kV transmission lines. Three work practices are compared: bare-handed work with live lines (the current practice at the example utility), use of hot sticks, and de-energizing lines prior to work. Bare-handed work with live lines leads to occasional exceedances of the 10 G TLV. Use of hot sticks and de-energizing lines eliminate these exceedances, but they do so at a price. Both practices increase the job duration and, as a result, may increase occupational injury risks. The annual costs for the current live-line, bare-handed practice is approximately $175,000. Use of hot sticks increases this annual cost of maintenance and repair by 30 to 55%. De-energizing lines can increase annual costs by $4 million to $14 million, due to the need for adding additional electricity generation during the planned outages. De-energizing lines also increases the risk to service reliability slightly.

Costs and Cost Analysis↗
PubMed2004

[The new German general threshold limit value for dust--pro and contra the adoption in Austria].

Since it has been realised that inhalation of inert dust is one of the important confounding variables for the development of chronic bronchitis, the threshold values for occupational exposure to these dusts needs to be further decreased. The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK-Commission) has set a new threshold (MAK-Value) for inert dusts (4 mg/m3 for inhalable dust, 1.5 mg/m3 for respirable dust) in 1997. This value is much lower than the threshold values currently used world-wide. The aim of the present article is to assess the scientific plausibility of the methodology (databases and statistics) used to set these new German MAK-Values, regarding their adoption in Austria. Although we believe that it is substantial to lower the MAK-Value for inert dust in order to prevent the development of chronic bronchitis as a consequence of occupational exposure to inert dusts, the applied methodology used by the German MAK-Commission in 1997 to set the new MAK-Values does not justify the reduction of the threshold limit value. A carefully designed study to establish an appropriate scientific basis for setting a new threshold value for inert dusts in the workplace should be carried out. Meanwhile, at least the currently internationally applied threshold values should be adopted in Austria.

Air Pollutants, Occupational↗
PubMed1983

Odor as an aid to chemical safety: odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution.

The body of information in this paper is directed to specialists in industrial health and safety, and air and water pollution, who need quantitative data on the odor thresholds of potentially hazardous chemical vapors and gases. The literature, largely unorganized, has been reviewed for 214 compounds and condensed into tables based on consistent units. Data on the volatility, solubility, ionization and water-air distribution ratio at 25 degrees C are included. From the currently recommended threshold limit value (TLV), a safe dilution factor and an odor safety factor are calculated for each compound. The equivalent data are presented for both air and water dilutions of the chemicals. Available data are summarized on the variability of odor sensitivities in the population, and the increased odor concentrations that are required to elicit responses from persons whose attention is distracted, or who are sleeping. This information is reduced to calibration charts that may be used to estimate the relative detectability, warning potential and rousing capacity of the odorous vapors. Each compound has been assigned a letter classification, from A to E, to indicate the margin of safety, if any, that may be afforded by the odor of the compound as a warning that its threshold limit value is being exceeded.

Environmental Exposure↗