Using Evidence Integration Techniques in the Development of Health-Based Occupational Exposure Levels.

Development of toxicology-based criteria such as occupational exposure levels (OELs) are rarely straightforward. This process requires a rigorous review of the literature, searching for patterns in toxicity, biological plausibility, coherence, and dose-response relationships. Despite the direct applicability, human data are rarely used primarily because of imprecise exposure estimates, unknown influence of assumptions, and confounding factors. As a result, high reliance is often placed on laboratory animal data. Often, data from a single study is typically used to represent an entire database to extrapolate an OEL, even for data-rich compounds. Here we present a holistic framework for evaluating epidemiological, controlled in vivo, mechanistic/in vitro, and computational evidence that can be useful in deriving OELs. It begins with describing a documented review process of the literature, followed by sorting of data into either controlled laboratory in vivo, in silico/read-across, mechanistic/in vitro, or epidemiological/field data categories. Studies are then evaluated and qualified based on rigor, risk of bias, and applicability for point of departure development. Other data (eg, in vitro, in silico estimates, read-across data and mechanistic information, and data that failed to meet the former criteria) are used alongside qualified epidemiological exposure estimates to help inform points of departure or human-equivalent concentrations that are based on toxic end points. Bayesian benchmark dose methods are used to estimate points of departure and for estimating uncertainty factors (UFs) to develop preliminary OELs. These are then compared with epidemiological data to support the OEL and the use and magnitude of UFs, when appropriate.

Identification of growth stage-specific watering thresholds for drought screening in Solanum aethiopicum Shum.

Effective phenotyping for drought resistance is a pre-requisite for identification of modest crop varieties for farmers. For neglected and underutilized crops such as Solanum aethiopicum Shum group, no drought screening protocol based on rigorous iterations has been documented. A split-plot nested treatment structure was arranged in an experiment to identify growth stage-specific watering thresholds for this crop. Three plant growth stages (main plot; seedling, vegetative and flowering), watering regime at plant growth stage (2 regimes; well-watered and drought stressed) and day since last watering at plant growth stage were evaluated for soil moisture content (SMC), leaf wilting score (LWS), number of green leaves per plant (LPP) and leaf blade width (LBW). Highly significant differences (p < 0.001) were found at the different plant growth stages, watering regime (WR) within plant growth stage, and day within WR and plant growth stage. Under drought stress treatment, SMC declined exponentially at each stage. The earliest leaf wilting, reduction in LPP and LBW were generally observed at flowering followed by vegetative and slowest at the seedling stage. For future effective drought phenotyping studies in S. aethiopicum Shum and related crops, we recommend setting minimum drought stress treatments below 18% SMC at which the LWS is ≥2 at the vegetative.

Normal Values for Cervical Vestibular-Evoked Myogenic Potentials.

OBJECTIVES: To assess the variability of normal values for cervical vestibular-evoked myogenic potentials (cVEMP) testing and to provide guidance regarding which parameters should be reported for clinical practice. STUDY DESIGN: Forty-eight normal subjects with no history of hearing loss or vestibular symptoms underwent cVEMP testing. Measurement parameters were tabulated and compared to other sets of cVEMP normal values in the literature. The literature was reviewed to assess the clinical significance of abnormal cVEMP results. The distributions of threshold and symmetry ratios for normal subjects were compared to the distributions of 90 patients who underwent cVEMP testing. SETTING: Tertiary academic center. RESULTS: Upper limits of 42% symmetry ratio and the range of 65 to 95 dB HL for threshold were established for our center.The quartile coefficients of dispersion were much less than 1.0 for all cVEMP parameters in the literature, suggesting that the variability in normal ranges across the literature is small. The distributions for threshold and symmetry ratio were similar between normal and patient groups. There is a lack of information in the literature regarding the impairment of function resulting from various degrees of abnormality of VEMP results. CONCLUSIONS: Normal values for cVEMP parameters are statistically consistent in the literature. The clinical significance of abnormal values has not been validated. For clinical purposes, cVEMP "thresholds" should be reported. Reporting of other parameters is optional.

Evaluation of the toxicity data for peracetic acid in deriving occupational exposure limits: a minireview.

Peracetic acid (PAA) is a peroxide-based chemistry that is highly reactive and can produce strong local effects upon direct contact with the eyes, skin and respiratory tract. Given its increasing prominence in industry, attention has focused on health hazards and associated risks for PAA in the workplace. Occupational exposure limits (OEL) are one means to mitigate risks associated with chemical hazards in the workplace. A mini-review of the toxicity data for PAA was conducted in order to determine if the data were sufficient to derive health-based OELs. The available data for PAA frequently come from unpublished studies that lack sufficient study details, suffer from gaps in available information and often follow unconventional testing methodology. Despite these limitations, animal and human data suggest sensory irritation as the most sensitive endpoint associated with inhalation of PAA. Rodent RD50 data (the concentration estimated to cause a 50% depression in respiratory rate) were selected as the critical studies in deriving OELs. Based on these data, a range of 0.36-0.51mg/m(3) (0.1-0.2ppm) was calculated for a time-weighted average (TWA), and 1.2-1.7mg/m(3) (0.4-0.5ppm) as a range for a short-term exposure limit (STEL). These ranges compare favorably to other published OELs for PAA. Considering the applicable health hazards for this chemistry, a joint TWA/STEL OEL approach for PAA is deemed the most appropriate in assessing workplace exposures to PAA, and the selection of specific values within these proposed ranges represents a risk management decision.

Perlite toxicology and epidemiology--a review.

Perlite is a generic name for an amorphous volcanic alumina-silicate rock that expands by a factor of 4-20 when rapidly heated to 1400-1800 °F (760-980 °C). Both the ore and the expanded product have extensive and widespread commercial applications. Limited data on the toxicology of perlite in animal studies indicate that the LD50 (oral ingestion) is more than 10 g/kg and, from a chronic inhalation study in guinea pigs and rats, that the NOAEL for the inhalation pathway is 226 mg/m³. Health surveillance studies of workers in US perlite mines and expansion plants (including some workers exposed to levels greater than prevailing occupational exposure limits (OELs) conducted over 20 years indicate that the respiratory health of workers is not adversely affected. Studies in Turkish mines and expanding plants had generally similar results, but are more difficult to interpret because of high smoking rates in these populations. A recent mortality study of permanent residents of the island of Milos (Greece) exposed to various mining dusts (including perlite) resulted in non-significant increases in standard mortality ratios for pneumonia and chronic obstructive pulmonary disease (COPD), whereas a companion morbidity study revealed elevated odds ratios for allergic rhinitis, pneumonia, and COPD when compared to another industrial area of Greece. Residents were exposed to other mining dusts and other possible causes or contributing factors and no ambient monitoring data were presented so it is not possible to use this study for risk calculations of perlite-exposed populations. Perlite is regulated as a "nuisance dust" in most countries.

Saúde pública e saúde dos oceanos: interface conceitual dos paradigmas e análise de elementos essenciais e não essenciais em organismos marinhos de um ecossistema de ressurgência / Public health and health of the oceans: the conceptual interface paradigms and analysis of essential and nonessential elements in marine organisms in an ecosystem upwelling

Neste estudo foi avaliada a condição de vulnerabilidade ambiental e da saúde humana em decorrência dos impactos e alterações observados nos oceanos nas últimas décadas, incluindo o foco sobre as mudanças climáticas, florações de algas tóxicas, contaminação microbiológica e química nas águas marinhas e bioinvasão de espécies exóticas. Além disso, foi abordada a relação dos valores benéficos que os oceanos proporcionam à saúde e bem-estar da humanidade. Esta primeira fase do estudo mostrou a interface entre o estado de conservação dos oceanos e sua relação com a economia e saúde humana. Mais adiante neste manuscrito foi realizado um estudo sazonal das concentrações de metais tóxicos (Hg, Al e As), micro (Zn, Cu, Fe, Se e Sr) e macronutrientes (Na, K, Ca e Mg) em amostras de músculo de lula (Loligo plei) e peixes marinhos pelágicos (Sardinella brasiliensis, Trichiurus lepturus e Coryphaena hippurus) com importância para a pesca, considerando o fenômeno temporal (inverno e verão) da ressurgência de Cabo Frio. As concentrações de As e Cu ultrapassaram os limites máximos de tolerância para o consumo humano. Foram observadas diferenças sazonais em alguns indivíduos, porém associação antagônica temporal entre as espécies, algumas apresentando concentrações mais elevadas durante o verão enquanto outras mostraram concentrações maiores no inverno para um determinando elemento. Foram encontradas diferenças significativas entre as concentrações detectadas nas diferentes espécies. No geral a lula (L. plei) e a sardinha-verdadeira apresentaram concentrações superiores dos elementos.

Foram detectadas correlações interelementares com destaque para associação entre Mg-Se e Ca-Sr. Um outra abordagem foi empregada com a finalidade de se estudar as concentrações de elementos tóxicos (Hg, Al e As), micronutrientes (Zn, Cu, Fe, Sr e Se) e macronutrientes (Na, K, Ca e Mg) em amostras de mexilhão (Perna perna), lula (Loligo plei), peixes pelágicos (Sardinella brasiliensis, Trichiurus lepturus e Coryphaena hippurus), tartaruga marinha (Chelonia mydas), ave marinha (Sula leucogaster) e mamíferos marinhos, incluindo duas espécies de golfinhos (Tursiops truncatus e Steno bredanensis) e uma espécie de baleia (Balaenoptera brydei). As coletas foram conduzidas na área de influência da ressurgência costeira de Cabo Frio, sendo estas espécies representativas deste hábitat. Foram encontradas diferenças significativas entre as concentrações detectadas nas diversas espécies. Uma distribuição trófica na concentração dos elementos foi percebida para Hg e Fe. Concentrações de Al também foram expressivamente elevadas para as amostras de lula e mexilhão. Foram observadas correlações interelementares significativas entre as espécies avaliadas variando para cada espécie. As concentrações de macronutrientes foram expressivas se comparadas aos demais estudos publicados. Os resultados encontrados mostram que a região de ressurgência de Cabo Frio parece exercer papel importante na biodisponibilização de elementos para a estrutura trófica marinha.

Evaluation of portable single-gas monitors for the detection of low levels of hydrogen sulfide and sulfur dioxide in petroleum industry environments.

Many portable single-gas monitors are used for the detection of low concentrations of hydrogen sulfide (H(2)S) and sulfur dioxide (SO(2)) in the workplace. With the recent lowering of the H(2)S and SO(2) ACGIH® threshold limit value (TLV®) the ability of these devices to selectively respond to these new lower levels is not well documented in petroleum industry environments, which often have potential interfering gases and vapors present as well as varying environmental conditions. Tests were carried out to measure the ability of various monitors with their respective sensors to correctly quantify and respond to H(2)S and SO(2) in a simulated petroleum industry environment. This included the identification of selected interference effects and estimation of the reliable lower limit of detection for real workplace environments. None of the H(2)S monitors responded at 0.1 times the new TLV (0.1 ppm), only some of them responded at the new TLV concentration (1 ppm), and all the monitors exposed to five times the new TLV (5 ppm) responded with reasonable accuracy. There was generally little effect of interferent gases and vapors on the H(2)S monitors. None of the SO(2) monitors responded at 0.1 and 1 times the new TLV (0.025 ppm and 0.25 ppm) concentrations, and all but one of them exposed to five times the new TLV (1.25 ppm) responded. There was much greater cross-sensitivity to interferents at the tested concentrations with the SO(2) monitors, which responded to six out of eight of the interferents tested. Results demonstrate that these monitors cannot reliably alarm and measure H(2)S or SO(2) concentrations at the new TLVs with an acceptable degree of accuracy. However, these monitors are designed to alarm as a safety device; these results do not change this important function.

A consistent and transparent approach for calculation of Derived No-Effect Levels (DNELs) for petroleum substances.

The REACH legislation introduced Derived No-Effect Levels (DNELs) which are defined as 'the levels of exposure above which humans should not be exposed'. DNELs were required for several categories of petroleum substances and CONCAWE developed a consistent approach for their derivation. First, the No-Observed Effect Level from a relevant study was corrected for pattern and route of exposure to obtain a modified Point-of-Departure (POD(modified)). Subsequently, the DNEL was calculated by dividing the POD(modified) by Assessment Factors (AFs) to adjust for inter- and intraspecies differences. If substance-specific information allowed, Informed Assessment Factors (IAFs), developed by CONCAWE were utilised. When little or no substance-specific information on those differences was known, default AFs from the guidance provided by ECHA were used. Some hazard endpoints did not lend themselves to calculation of DNELs (e.g. aspiration, dermal irritation, mutagenicity). DNEL calculation was considered not appropriate if adverse effects were not observed in tests conducted at a limit dose or if meaningful dose-response curves could not be developed. However, DNELs were calculated when hazards were identified, regardless of whether or not risk characterisation was required under REACH. Examples for gasoline, Lubricating Base Oils, gas oils and bitumen are provided to illustrate CONCAWE's approach.

Use of the reciprocal calculation procedure for setting workplace emergency action levels for hydrocarbon mixtures and their relationship to lower explosive limits.

This paper proposes a novel use of the reciprocal calculation procedure (RCP) to calculate workplace emergency action levels (WEALs) for accidental releases of hydrocarbon mixtures. WEALs are defined here as the concentration in air that area monitors should alarm at to provide adequate warning and be sufficiently protective of health to allow at least enough time to don respiratory protective equipment (RPE) and escape. The rationale for the approach is analysed, and ways of defining suitable substance group guidance values (GVs) for input into the RCP are considered and compared. WEAL GVs could be based on: 3× RCP GVs (i.e. using the 3× rule), the 5× RCP GVs (i.e. using the 5× rule for calculating ceiling values), emergency exposure limits, or immediately dangerous to life or health values (IDLHs). Of these, the method of choice is to base WEAL GVs on health-based IDLH values, which were developed for emergency situations in the workplace. However, IDLHs have only been set for 11 hydrocarbons, so the choice of GVs is also informed by comparison with possible GVs based on the other approaches. Using the proposed GVs, WEALs were calculated for various hydrocarbon mixtures, and the way they vary with the composition of the mixture was examined. Also, the level of health protection given by the current practice of setting emergency area alarms in the oil and gas industry at 10% of the lower explosive limit (LEL) was tested by comparing this with the WEAL. In the event of an accidental release, this comparison suggests that, provided that aromatics constitute <50% of the mixture, an alarm set at 10% LEL should provide adequate warning and be sufficiently protective of health to at allow at least enough time to don RPE and escape. In the absence of better information or specific acute toxicity concerns (such as the presence of hydrogen sulphide), it is proposed that the WEALs be used as a guide for assessing the adequacy of area alarm levels in respect of warning of an acute health risk. This work is exploratory (e.g. other rationales for setting GVs are possible) and the approach needs testing on further real-life samples. Although not explored here, the RCP approach may also lend itself to the calculation of in-house short-term exposure limits for hydrocarbon mixtures and other mixtures where the acute toxic end points of the components are similar.

An in silico canine cardiac midmyocardial action potential duration model as a tool for early drug safety assessment.

Cell lines expressing ion channels (IC) and the advent of plate-based electrophysiology device have enabled a molecular understanding of the action potential (AP) as a means of early QT assessment. We sought to develop an in silico AP (isAP) model that provides an assessment of the effect of a compound on the myocyte AP duration (APD) using concentration-effect curve data from a panel of five ICs (hNav1.5, hCav1.2, hKv4.3/hKChIP2.2, hKv7.1/hminK, hKv11.1). A test set of 53 compounds was selected to cover a range of selective and mixed IC modulators that were tested for their effects on optically measured APD. A threshold of >10% change in APD at 90% repolarization (APD(90)) was used to signify an effect at the top test concentration. To capture the variations observed in left ventricular midmyocardial myocyte APD data from 19 different dogs, the isAP model was calibrated to produce an ensemble of 19 model variants that could capture the shape and form of the APs and also quantitatively replicate dofetilide- and diltiazem-induced APD(90) changes. Provided with IC panel data only, the isAP model was then used, blinded, to predict APD(90) changes greater than 10%. At a simulated concentration of 30 µM and based on a criterion that six of the variants had to agree, isAP prediction was scored as showing greater than 80% predictivity of compound activity. Thus, early in drug discovery, the isAP model allows integrating separate IC data and is amenable to the throughput required for use as a virtual screen.

Performance of high flow rate samplers for respirable particle collection.

The American Conference of Governmental Industrial hygienists (ACGIH) lowered the threshold limit value (TLV) for respirable crystalline silica (RCS) exposure from 0.05 to 0.025 mg m(-3) in 2006. For a working environment with an airborne dust concentration near this lowered TLV, the sample collected with current standard respirable aerosol samplers might not provide enough RCS for quantitative analysis. Adopting high flow rate sampling devices for respirable dust containing silica may provide a sufficient amount of RCS to be above the limit of quantification even for samples collected for less than full shift. The performances of three high flow rate respirable samplers (CIP10-R, GK2.69, and FSP10) have been evaluated in this study. Eleven different sizes of monodisperse aerosols of ammonium fluorescein were generated with a vibrating orifice aerosol generator in a calm air chamber in order to determine the sampling efficiency of each sampler. Aluminum oxide particles generated by a fluidized bed aerosol generator were used to test (i) the uniformity of a modified calm air chamber, (ii) the effect of loading on the sampling efficiency, and (iii) the performance of dust collection compared to lower flow rate cyclones in common use in the USA (10-mm nylon and Higgins-Dewell cyclones). The coefficient of variation for eight simultaneous samples in the modified calm air chamber ranged from 1.9 to 6.1% for triplicate measures of three different aerosols. The 50% cutoff size ((50)d(ae)) of the high flow rate samplers operated at the flow rates recommended by manufacturers were determined as 4.7, 4.1, and 4.8 microm for CIP10-R, GK2.69, and FSP10, respectively. The mass concentration ratio of the high flow rate samplers to the low flow rate cyclones decreased with decreasing mass median aerodynamic diameter (MMAD) and high flow rate samplers collected more dust than low flow rate samplers by a range of 2-11 times based on gravimetric analysis. Dust loading inside the high flow rate samplers does not appear to affect the particle separation in either FSP10 or GK2.69. The high flow rate samplers overestimated compared to the International Standards Organization/Comité Européen de Normalisation/ACGIH respirable convention [up to 40% at large MMAD (27.5 microm)] and could provide overestimated exposure data with the current flow rates. However, both cyclones appeared to be able to provide relatively unbiased assessments of RCS when their flow rates were adjusted.

Metal impurities in food and drugs.

The major metals of potential health concern found in food, drugs (medicines), and dietary supplements are lead, cadmium, mercury, and arsenic. Other metals, such as chromium, copper, manganese, molybdenum, vanadium, nickel, osmium, rhodium, ruthenium, iridium, palladium, and platinum, may be used or introduced during manufacturing and may be controlled in the final article as impurities. Screening for metals in medicines and dietary supplements rarely indicates the presence of toxic metal impurities at levels of concern. The setting of heavy metal limits is appropriate for medicines and is appropriate for supplements when heavy metals are likely or certain to contaminate a given product. Setting reasonable health-based limits for some of these metals is challenging because of their ubiquity in the environment, limitations of current analytical procedures, and other factors. Taken together, compendial tests for metals in food and drugs present an array of issues that challenge compendial scientists.

Stimulus-dependent processing of temporal order.

Two distinct conceptualisations of processing mechanisms have been proposed in the research on the perception of temporal order, one that assumes a central-timing mechanism that is involved in the detection of temporal order independent of modality and stimulus type, another one assuming feature-specific mechanisms that are dependent on stimulus properties. In the present study, four different temporal-order judgement tasks were compared to test these two conceptualisations, that is, to determine whether common processes underlie temporal-order thresholds over different modalities and stimulus types or whether distinct processes are related to each task. Measurements varied regarding modality (visual and auditory) and stimulus properties (auditory modality: clicks and tones; visual modality: colour and position). Results indicate that the click and the tone paradigm, as well as the colour and position paradigm, correlate with each other. Besides these intra-modal relationships, cross-modal correlations show dependencies between the click, the colour and the position tasks. Both processing mechanisms seem to influence the detection of temporal order. While two different tones are integrated and processed by a more independent, possibly feature-specific mechanism, a more central, modality-independent timing mechanism contributes to the click, colour and position condition.

[Integration of biological and workplace monitoring as an efficient control of chemical exposure]. / Integrazione dei piani di monitoraggio degli indicatori biologici di esposizione e dei piani di monitoraggio ambientale/espositivo.

Evaluation of professional exposure by means of biological monitoring is nowadays a consolidated method in the practice of Occupational Health. Generally biological monitoring is used simultaneously to ambient monitoring as a complementary method to obtain a mutual validation of exposure assessment. Experience gathered in the last years allowed us to verify that at low exposure levels, the values of biological indicators of dose are always markedly below their limits. Consequently, under standard conditions, it appears useful to alternate the two different exposure assessments (either biological or ambient monitoring), in order to obtain an efficient control of chemical exposure. Moreover, this methodological approach allows a better integration of all the professionals, who manage directly or indirectly the activities concerning Occupational Health and Industrial Hygiene, having as their first goal the health protection of employees and job environment.

The nervous system effects of occupational exposure to manganese--measured as respirable dust--in a South African manganese smelter.

OBJECTIVES: A major recent review of occupational exposure limits for manganese (Mn) has proposed a respirable dust level of 0.1 mg/m3. There is, however, no theoretical basis for using this exposure metric to estimate the systemic effects of Mn, and little in the way of empirical data relating respirable Mn to neurobehavioural and other non-pulmonary effects. Cross-sectional data from a study showing few and unconvincing neurobehavioural effects of inhalable dust in Mn smelter workers published just prior to this review were reanalyzed here using respirable Mn. The hypotheses tested were that respirable Mn exposure is a more appropriate predictor of neurobehavioural effects than inhalable Mn where such effects exist, and that there should be no observed effects at respirable dust levels below 0.1 mg/m3. METHODS: Five hundred and nine production workers and 67 external referents were studied. Exposure measures from personal sampling included the Mn content of respirable dust as a concentration-time integrated cumulative exposure index (CEI) and as average intensity (INT) over a working lifetime. Neurobehavioural endpoints included items from the Swedish nervous system questionnaire (Q16), World Health Organisation neurobehavioural core test battery (WHO NCTB), Swedish performance evaluation system (SPES), Luria-Nebraska (LN), and Danish Product Development (DPD) test batteries, and a brief clinical examination. RESULTS: The median respirable Mn exposure was 0.058 mg/m3 (range=0-0.51; IQR=0.02-0.16) amongst the exposed, with 30% having average intensities above the proposed 0.1 mg/m3 and 44% above the proposed supplemental limit of 0.5 mg/m3 inhalable dust. As in the study of inhalable Mn effects, there were few respirable Mn effects showing clear continuity of response with increasing exposure. CONCLUSION: These data did not provide empirical support for a respirable, as opposed to an inhalable, dust metric being more sensitive in the identification of Mn effects. Neither metric showed convincing effects within the exposure range studied. Further study is needed to determine a threshold for respirable Mn effects, if such exist, and to verify our findings.

European hazard classification advice for crude oil-derived lubricant base oils compared with the proposed mineral oil mist TLV.

The notice of intended change for the threshold limit value (TLV) for mineral oil mist contains a notation for human carcinogenicity. A description is provided of the current European regulatory approach used to distinguish between carcinogenic and non-carcinogenic mineral base oils on the basis of oil refining process and chemical marker information. This approach has proven effective in creating a market situation in the countries of the European Union where many customers require severely refined, non-carcinogenic oils. It is recommended that ACGIH consolidate the distinction between poorly and severely refined base oils in the recommended TLV for mineral oil mist and use different toxicological considerations to derive exposure control guidelines.

Lung counting: summing techniques to reduce the MDA.

The new dose limits recently adopted in Canada (and elsewhere in the world) have made it more difficult to detect some radionuclides by in vivo counting at the average dose limit of 20 mSv. This is particularly true for natural uranium. Two techniques have been developed by the Human Monitoring Laboratory to reduce the Minimum Detectable Activity (MDA) for the lung counting of this nuclide. The first technique, developed in collaboration with Cameco, is to either sum sequential counts of an individual or to sum spectra of a group of workers similarly occupationally exposed. This technique offers a reduction in the MDA of up to a factor of three. The second technique, developed in collaboration with CNEN, involves the summing of photopeaks within an individual spectrum and offers a reduction in the MDA of up to a factor of two.

Should the threshold limit value for power frequency (60 Hz) magnetic fields be changed? Perceptions among scientists and other risk experts.

Over the past few years several studies have raised questions about childhood cancer and exposure to electric and magnetic fields (EMFs). Reports by the National Academy of Sciences and the National Cancer Institute concluded that there is no clear, convincing evidence that exposure to electric power lines and electric power appliances is a threat to human health, whereas the National Institute of Environmental Health Sciences concluded that there is weak evidence that EMF exposure may be a leukemia hazard. Based on the conflicting agency reports on EMF, what do experts in the field of bioelectromagnetics believe regarding the effectiveness of the American Conference of Governmental Industrial Hygienists (ACGIH) guidelines? Surveys were sent to 163 participants at the 1997 annual Department of Energy Contractors meeting on Electric and Magnetic Fields. Approximately one-half (49%, n = 81) of the participants returned the survey. Utility workers demonstrated greater levels of agreement with the current TLV standard in comparison to government, university, and other private sector workers. Utility workers were less likely to perceive that ACGIH guidelines should be changed to be made more strict. In addition, workers who had worked at their present job for 10 years or more indicated less agreement with the acceptability of ACGIH guidelines to protect workers' health. The scientists and other risk experts in this study illustrate the importance of how type of industry may influence perceptions of TLV effectiveness.