MCPA permeation through protective gloves

Permeation of 4-chloro-2-methylphenoxyacetic acid (MCPA) in commercial herbicide formulations through common protective glove types was evaluated to aid in the selection of appropriate skin protection. The ASTM test method F739-91 was used to measure the permeation of two undiluted formulations, one containing a salt, and the other an ester form of MCPA. The four glove types tested were natural rubber, neoprene 73, nitrile 37-145, and Viton-coated chloroprene. Triplicate tests of each combination of formulation and glove material were conducted. Permeation cells with a 0.01 M sodium hydroxide collection medium were used for the experiments. Aliquots of the collection medium were withdrawn at regular intervals and acidified, and quantification of the free acid was achieved using HPLC-UV (230 nm). There was no appreciable permeation of the salt formulation over a 24-hour test period. For the ester formulation, the following mean steady-state permeation rate (microg x cm(-2) min(-1)) and mean lag time (hours), respectively, were measured: Viton (0.06, 17.8), natural rubber (0.08, 15.4), neoprene 73 (0.21, 15.1), and nitrile (0.04, 24.2). Permeation was associated with significant swelling, averaging a nearly 30 percent increase from the pre-immersion thickness. All four glove types provide adequate protection against permeation by the salt formulation and at least eight-hour protection against the ester formulation. Given the greater permeation of the ester formulation, the salt formulation of MCPA herbicide should be used whenever possible.

The development of a new method to estimate total daily dose of pesticides in professional turf applicators following multiple and varied exposures in occupational settings

The evaluation of absorbed dose of pesticides in humans requires a knowledge of the kinetics and dynamics of the compound. In some circumstances, data that allow for the estimation of dose may be available from human volunteer studies, although often, it will be based on results from animal studies. If human metabolism data are available, estimates of dose may be more accurate, but it should be recognized that pesticide exposure in an occupational setting may differ from that in a controlled laboratory study. In this study, data from previously published studies are used to evaluate the urinary excretion of 2,4-dichlorophenoxyacetic acid (2,4-D), following single dermal applications to human volunteers. These studies are evaluated with the objective of determining the best method of predicting total absorbed dose following multiple and varied exposures in occupational settings. Further, an alternative to laboratory-controlled human volunteer studies is presented. Data from a third previously published biological monitoring study on six professional pesticide applicators over a 2-week period were used to generate estimates of the urinary excretion of the pesticide 2,4-D that would result from a single dose. The method used to estimate the urinary excretion parameters is a variation of an overlay technique used in pharmacology, and may provide information on the kinetics of other pesticides when it is not possible to conduct human studies. The generated estimates of 24-h urinary excretion of 2,4-D over a 6-day period were remarkably similar to those obtained in controlled studies. Finally, a method was developed to use the generated estimates to determine total absorbed dose of pesticides for an independent group of 95 professional pesticide applicators. This method requires information on the amount of pesticide used for 6 days prior to the collection of two, 24-h urine samples.

An evaluation of 24-hour urinary creatinine excretion for use in identification of incomplete urine collections and adjustment of absorbed dose of pesticides

The accurate quantification of the absorbed dose of pesticides following occupational exposures generally requires complete 24-hour urine collections, often over extended periods of time. Difficulty in obtaining volunteer cooperation may result in incomplete urine collections. Traditionally, 24-hour urinary creatinine has been used to identify incomplete urine samples and has been used to standardize pesticide and other chemical dose estimates. More recently, the use of creatinine to standardize dose estimates has been questioned, as has its utility in the identification of incomplete urine collections. This research evaluates the use of personal observation, statistical methods, and published models to predict creatinine excretion to identify and adjust for incomplete urine collections. Based on the use of published creatinine prediction models, an evaluation of the day-to-day creatinine excretion within subjects, and personal observation, a small number of suspected urine samples were identified. Although it is likely that these samples were incomplete, correction of these urine volumes based on the published models did little to improve pesticide dose prediction. Further, results indicate that subjects who report missed urine samples may be able to estimate the missing volumes with some accuracy. In future pesticide exposure studies, the use of self-reported missed volumes may help to increase the accuracy of dose prediction when there is strong cooperation with collection procedures. A statistical model to predict creatinine excretion in professional turf applicators was developed to provide a preliminary screening for urinary completeness for future studies in which compliance with urinary collection is thought to be insufficient.

An investigation of the association between exposure to styrene and hearing loss

The importance of the association between advancing age and hearing loss is well recognized. Further, prolonged significant noise exposures are also known to result in permanent hearing loss. However, little is known of the contribution of industrial chemical exposures to hearing loss. Information available, from both animal and human studies, raises the possibility that certain aromatic hydrocarbons are ototoxic. The purpose of this study was to assess whether occupational styrene exposure causes hearing loss in a group of workers in the fiber-reinforced plastics manufacturing industry. The hearing acuity of 299 subjects was determined, using pure-tone screening audiometry, at the beginning of a single workshift and again at the end of the shift. On the same day, the personal, time-weighted average exposures of each subject to both styrene and noise were measured. In addition, information on the following factors was obtained from each participant: previous work history, including exposures to noise and chemicals; use of personal protective equipment for noise or solvents; personal and family history of hearing problems; and smoking history. Current exposures together with work histories were used to construct lifetime noise and styrene exposure indices. No conclusive evidence was found for a chronic styrene-induced effect on hearing acuity, when both noise and styrene lifetime exposures were taken into account. As expected, age and noise exposures were highly important variables, both positively associated with hearing loss. In addition, the detrimental effect of noise exposure on hearing acuity was found to be strengthened with increased age. Noise and styrene exposures were highly correlated, clearly illustrating the importance of considering all associated variables in analysis of such data. No evidence was found for a relationship between smoking, recreational noise, solvent exposures, and hearing loss.

Evaluation of professional competency in occupational hygiene in Canada--the CRBOH program. Canadian Registration Board of Occupational Hygienists

The Canadian Registration Board of Occupational Hygienists (CRBOH) was established in 1986 to provide a registration system for professional occupational hygienists in Canada. It was decided that registration would be based on a competency examination following an appropriate combination of academic qualification and relevant professional experience. While the examination was being developed hygienists who met certain educational and experience requirements and who held other certifications by examination (such as those of the American Board of Industrial Hygiene, the British Examining and Board in Occupational Hygiene, or the Conseil d'Accrediation en Hygiene Industrielle du Quebec) were registered. In 1989 CRBOH, after much deliberation and review of other existing certification examinations, selected a two-part scheme consisting of both written and oral examinations. The written examination includes both multiple choice and essay style questions. Only those candidates successfully completing the written examination are eligible for the oral examination. The first group of candidates was examined in the fall of 1990. The authors outline the strengths and weaknesses of various forms of evaluation of professional competency. The rationale for the selection of the CRBOH examination format is discussed in relation to forms of evaluation currently being used in the United States and the United Kingdom. The implication of CRBOH registration on the training and education of occupational hygienists in Canada is highlighted.

Exposure of hospital operating room personnel to potentially harmful environmental agents

Epidemiologic studies of risk to reproductive health arising from the operating room environment have been inconclusive and lack quantitative exposure information. This study was undertaken to quantify exposure of operating room (OR) personnel to anesthetic agents, x-radiation, methyl methacrylate, and ethylene oxide and to determine how exposure varies with different operating room factors. Exposures of anesthetists and nurses to these agents were determined in selected operating rooms over three consecutive days. Each subject was asked to wear an x-radiation dosimeter for 1 month. Exposure to anesthetic agents was found to be influenced by the age of the OR facility, type of surgical service, number of procedures carried out during the day, type of anesthetic circuitry, and method of anesthesia delivery. Anesthetists were found to have significantly greater exposures than OR nurses. Exposure of OR personnel to ethylene oxide, methyl methacrylate, and x-radiation were well within existing standards. Exposure of anesthetists and nurses to anesthetic agents, at times, was in excess of Ontario exposure guidelines, despite improvements in the control of anesthetic pollution.

Wood dust and formaldehyde exposures in the cabinet-making industry

Time-weighted average (TWA) personal total and respirable dust exposures were determined gravimetrically for 48 subjects in 4 cabinet-making plants. TWA personal formaldehyde exposures also were obtained, with the use of 3M 3750 passive monitors. Selective area sampling for formaldehyde was undertaken using two methods. The results obtained with the passive monitors were compared to the standard chromotropic acid impinger method. Considerable variation was noted in the dust exposures. Cabinet-makers exposed to softwoods were found to have a mean exposure of approximately one half of the current applicable ACGIH TWA-TLV, while hard-wood exposure was twice the applicable TWA-TLV. The highest dust exposures were recorded for those workers sanding, the mean total dust being 2.91 mg/m3 (S.E. 0.70) and respirable dust 0.63 mg/m3 (S.E. 0.20). Sanding operations also were found to produce a higher proportion of respirable dust (22%) than other woodworking operations (6%-14%). Workers in assembly areas also were found to have higher dust exposures, likely reflecting the fact that conventional dust collection devices for stationary woodworking equipment are not appropriate for hand held tools and hand sanding. The importance of making respirable dust measurements is discussed. The poor correlation between paired total and respirable dust concentrations indicates that both measurements should be made. Some potential limitations to respirable wood dust sampling using 10 mm nylon cyclones are noted, however. Area dust concentrations were found to be significantly lower than personal exposures, emphasizing the importance of personal sampling data. Formaldehyde vapor exposures were very low, with a mean of 0.06 ppm (S.E. 0.01).

An accidental discharge of a Halon 1301 total flooding fire extinguishing system

An accidental discharge of a total flooding Halon 1301 fire extinguishing system is described. The release of the Halon was accompanied by a sudden very loud noise, considerable air turbulence and a dense fog, resulting in worker anxiety and loss of visibility. The workers in the area at the time of the discharge reported higher frequencies of lightheadedness, headache, nasal complaints and disorientation than those entering the area later. Halon 1301 usually is regarded as having a low toxicity, although at concentrations above those used in occupied spaces, effects on consciousness and cardiac rhythm have been reported. In the present report no significant illness or injury due to the Halon exposure was found. A fine oily deposit found on horizontal surfaces in the area subsequent to the discharge consisted of mineral oil and iron, suggesting that this material was scoured out of the piping as the Halon discharged. The disorientation and anxiety produced by an accidental discharge can be minimized through education programs designed to ensure that personnel know what to expect and how to abort the discharge if it results from a false alarm. Situations leading to triggering of fire detectors by events other than fires should be investigated and reduced.

Respiratory function and exposure-effect relationships in wood dust-exposed and control workers

The effect of wood dust exposure on 50 cabinet makers was examined. Woodworkers reported more nasal and eye symptoms and more cough, sputum and wheezing than did 49 control workers. More irritated cells were present in the woodworkers' nasal cytological smears. In contrast to the control workers, the woodworkers had a significant decline in lung function over the workshift. An inverse correlation between baseline lung function and an exposure index (mean area dust level multiplied by length of exposure) was demonstrated in the woodworkers. Greater dust exposure was not associated with larger falls in lung function over the work shift.

Exposure of operating room personnel to anaesthetic agents: an examination of the effectiveness of scavenging systems and the importance of maintenance programs

Ten Alberta hospitals were monitored to assess the exposure of operating room personnel to nitrous oxide, halothane and enflurane during the average work day. Exposure to these agents in operating rooms without scavenging systems was determined to be well above the recommended guidelines. Contaminants were significantly lower in operating rooms with scavenging systems of either the wall suction type or the air-conditioning exhaust type. In the majority of studies, leakage points of anaesthetic gases were found throughout the anaesthesia systems. Where maintenance programs for the anaesthesia equipment were designed for the detection and elimination of leakage, contaminant levels were significantly lower than in those hospitals where the maintenance programs were concerned solely with proper equipment function as it relates to patient care. A regular, frequent maintenance program for all anaesthesia and scavenging systems designed to identify and correct leakage points is therefore recommended. We consider a nitrous oxide monitor to be the ideal tool for detection of leakage.