Particulate matter emitted from ultrasonic humidifiers-Chemical composition and implication to indoor air.

Household humidification is widely practiced to combat dry indoor air. While the benefits of household humidification are widely perceived, its implications to the indoor air have not been critically appraised. In particular, ultrasonic humidifiers are known to generate fine particulate matter (PM). In this study, we first conducted laboratory experiments to investigate the size, quantity, and chemical composition of PM generated by an ultrasonic humidifier. The mass of PM generated showed a correlation with the total alkalinity of charge water, suggesting that CaCO3 is likely making a major contribution to PM. Ion chromatography analysis revealed a large amount of SO42- in PM, representing a previously unrecognized indoor source. Preliminary results of organic compounds being present in humidifier PM are also presented. A whole-house experiment was further conducted at an actual residential house, with five low-cost sensors (AirBeam) monitoring PM in real time. Operation of a single ultrasonic humidifier resulted in PM2.5 concentrations up to hundreds of µg m-3 , and its influence extended across the entire household. The transport and loss of PM2.5 depended on the rate of air circulation and ventilation. This study emphasizes the need to further investigate the impact of humidifier operation, both on human health and on the indoor atmospheric chemistry, for example, partitioning of acidic and basic compounds.

Striving to provide opportunities for farm worker community participation in research.

Hispanic farm workers and their families in the U.S. face a number of environmental and occupational health risks, yet they are rarely given the opportunity to choose the focus of the research and interventions that take place in their communities. Community-based participatory research (CBPR) can be one effective approach to changing this situation. CBPR is an approach to research that makes community members partners in research rather than subjects of research. This article describes the experience of El Proyecto Bienestar (The Well-Being Project), a CBPR project in the Yakima Valley, Washington, with the aim of facilitating the Hispanic community's involvement in the identification and prioritization of occupational and environmental health issues among farm workers. The project utilized three forms of data collection (key informant interviews, community surveys, and a town hall meeting) to create a list of environmental and occupational health issues of concern. Investigators strove to provide opportunities for community participation in the various stages of research: study concept and design, data collection, data analysis and interpretation, conclusions, and dissemination of results. This article describes the involvement that community members had at each stage of the three forms of data collection and outlines the basic findings that led the Community Advisory Board to prioritize four areas for future work. In addition, it describes the challenges the project faced from the researcher perspective. Using examples from this experience, we conclude that this model may be an effective way for farm workers and their families to have a voice in prioritizing health and safety issues for research and action in their communities.

Comparison of local risk factors for children's atopic symptoms in Hanoi, Vietnam.

BACKGROUND: A 1999 study in Hanoi, Vietnam using the International Study on Asthma and Allergies in Childhood (ISAAC) questionnaire showed a high prevalence of atopic symptoms. Identifying risk factors for symptoms in these children may help in understanding the causes for these high estimates. METHODS: An ISAAC questionnaire with supplemental questions on environmental variables was distributed to 5495 school children in Hanoi and a suburban district, Dong Anh. The response rate was 65.7%. RESULTS: In Dong Anh, the following were among the significant age and gender adjusted associations: pig ownership [odds ratio (OR) (95% confidence interval), OR = 1.79 (1.18-2.70) for doctor-diagnosed asthma (DDA), OR = 1.72 (1.08-2.78) for doctor diagnosed hay fever (DDHF)] and farming [OR = 1.67 (1.27-2.19) for ever asthma, OR = 1.51 (1.09-2.09) for DDHF]. In multivariate models, tuberculosis (TB) was a significant predictor of atopic symptoms [Hanoi: OR = 3.09 (1.10-8.70) for DDA, Dong Anh: OR = 3.71 (1.40-9.84) for DDA, OR = 4.66 (1.88-11.57) for DDHF]. CONCLUSIONS: These findings are contrary to the "hygiene hypothesis". Recent immunologic and epidemiologic studies refute the inverse association between allergy and TB and may be one explanation for the positive association in this study. The positive association with pig ownership and farming may be because of exposures on farms in a developing country that may be different from exposures in farms of developed countries.

Muscular strength and vibration thresholds during two years after acute poisoning with organophosphate insecticides.

AIMS: To evaluate the association of acute organophosphate (OP) poisoning with chronic sensory and motor neurological impairment. METHODS: This study concerns the third of a series of three examinations of hand strength and vibration thresholds in a two year period after acute OP poisoning among 48 Nicaraguan men. The first two examinations were performed at hospital discharge and seven weeks after poisoning, and the present examination two years later. Twenty eight cattle ranchers and fishermen who had never experienced pesticide poisoning were examined as controls, also three times over the two year period. The poisonings were categorised as caused by "non-neuropathic" OPs and "neuropathic" OPs, each subdivided in moderate and severe poisonings. RESULTS: Men poisoned with OP insecticides had persistent reduced hand strength. We previously reported weakness at hospital discharge for OP poisoned in all categories that worsened seven weeks later for those severely poisoned with neuropathic OPs. Strength improved over time, but the poisoned were still weaker than controls two years after the poisoning, most noticeably among the subjects most severely poisoned with neuropathic OPs. Also, index finger and toe vibration thresholds were slightly increased at the end of the two year period, among men with OP poisonings in all categories, but patterns of onset and evolvement of impairment of vibration sensitivity were less clear than with grip and pinch strength. CONCLUSIONS: Persistent, mainly motor, impairment of the peripheral nervous system was found in men two years after OP poisoning, in particular in severe occupational and intentional poisonings with neuropathic OPs. This finding is possibly due to remaining organophosphate induced delayed polyneuropathy.

A community-based telephone survey of work and injuries in teenage agricultural workers.

In order to estimate the one-year cumulative incidence of work-related injuries in teenage agricultural workers and to characterize the patterns and types of agricultural work performed by teenagers, we performed a community-based random-digit dialing telephone survey. We used a sampling frame of farm and non-farm households to access information on teenage agricultural workers. An agricultural community in eastern Washington State was selected due to the high number of teenage youth and its agricultural economy. Teenage agricultural workers who worked for an agricultural business owned by one of their family members were more likely to work a greater number of seasons, work fewer hours per week, perform tasks involving driving, animal care, and mechanic work, and were less likely to be seasonal workers or work in the harvest than teenagers who did not work for a family member. A similar pattern of work differences was seen when comparing non-Hispanic to Hispanic agricultural workers. Teenagers working for a family member in agriculture had a higher injury rate than teenagers working for an agricultural business not owned by a family member. The injury rate among Hispanic teenage agricultural workers was also higher than that of non-Hispanics.

Brain SPECT: a controlled, blinded assessment of intra-reader and inter-reader agreement.

A detailed assessment of intra- and inter-reader variation in the interpretation of brain SPECT scans has been performed. A random sample was selected from scans performed at a community/teaching hospital in Seattle. Scans were interpreted independently by three experienced readers who were blinded to all patient information. Forty-eight scans were interpreted twice by each reader, for a total of 288 readings. Readers recorded detailed assessments of individual lesions and overall impressions using a standardized reporting form. Intra-observer agreement as reflected in per cent agreement for severity scores ranged from 65% to 100%. Intra-observer agreement on the 'overall impression' was very good for Alzheimer's pattern (kappa=0.73-1.00), and fair to good for the 'heterogeneous pattern' (kappa=0.30-0.63). Inter-observer agreement, as reflected in per cent agreement, ranged from 29% to 100%. Inter-observer agreement about the 'overall impression' was fair to moderate for Alzheimer's pattern (kappa=0.24-0.54) and was poor for the descriptors 'heterogeneous' and 'normal'. It is concluded that brain SPECT has great potential value in many important conditions. This study demonstrates a need for further work in the areas of pattern definition and reduction of observer variation.

Validity study of self-reported pesticide exposure among orchardists.

Self-reported work histories are often the only means of estimating occupational exposures in epidemiologic research. The objective of this study was to examine the accuracy of recall of historical pesticide use among orchardists. All 185 orchardists in this study had participated previously in a cohort study of men occupationally exposed to pesticides. In that study (1972 to 1976), subjects were interviewed annually and asked to list pesticides used since the last interview. In 1997, 265 of the 440 presumed-living orchardists from the original cohort were successfully recontacted and asked to complete a detailed questionnaire concerning their lifetime use of pesticides; 185 (69.8% of farmers successfully contacted) agreed. Considering the 1972-1976 data as the standard, sensitivity and specificity of recall were calculated for certain pesticides and pesticide categories. Sensitivity of recall was good to excellent (0.6-0.9) for the broad categories of insecticides, herbicides, and fungicides, for heavily used chemical classes, such as organophosphates and organochlorines, and for commonly used pesticides; it was lower and more variable (0.1-0.6) for specific pesticides. Recall specificity was greatest (0.7-0.9) for the least used pesticides and chemical classes, such as dithiocarbamates and manganese-containing pesticides, and was generally modest for the rest (0.5-0.6). There was no evidence of selection bias between study participants and nonparticipants. In conclusion, recall accuracy was good for commonly used pesticides and pesticide categories. This level of recall accuracy is probably adequate for epidemiologic analyses of broad categories of pesticides, but is a limitation for detecting more specific associations.

Development of a life events/icon calendar questionnaire to ascertain occupational histories and other characteristics of migrant farmworkers.

BACKGROUND: Specialized methods are necessary to collect data from migrant farmworkers for epidemiologic research. METHODS: We developed a questionnaire that collected lifetime occupational histories and other lifestyle risk factors via a life events/icon calendar, and administered the questionnaire to a convenience sample of 162 migrant farmworkers in nine areas of the U.S. RESULTS: The average duration of the interviews was about 1 h 30 min, with an average of 45 min for the work history section. The occupational histories covered a median of 27.6 years per person for men and 20.8 years per person for women. The median number of years spent in farm jobs was 11.3 for men and 5.8 for women. The median number of farm jobs (crop/task combination) per person was 59 among men and 27 among women. Many farmworkers performed the same crop/task combinations at multiple times throughout their lives, yielding a median of 13 unique farm jobs and 8 unique crops among men and 7 jobs and 5 crops among women. CONCLUSIONS: The project demonstrated that it is feasible to collect detailed work histories and other risk factor data from farmworkers, documented the complexity of work histories encountered among farmworkers, and yielded recommendations for refining a questionnaire that will facilitate future epidemiologic research on farmworkers.

Test-retest reliability of an icon/calendar-based questionnaire used to assess occupational history.

BACKGROUND: Self-reported work histories can be critical for both epidemiologic and clinical purposes. However, the complexity of some work histories, such as those of migrant farm workers, can hamper recall, resulting in inaccurate reporting. Memory aids may reduce such error. This study assesses the reliability of work histories collected using such aids in the form of an icon/calendar-based questionnaire. METHODS: Thirty-one males engaged in farmwork and other manual labor for a median 28 years (range: 10-64) were interviewed twice, 8-14 months apart, about their lifetime employment. In each interview, subjects were asked about important life events, which were recorded with icons on a calendar. They were then asked to recount their work history, including for each job the tasks, crops or products handled, starting and ending dates, and location. This information was recorded, job-by-job, on the calendar with icons. RESULTS: Interquestionnaire agreement of cumulative reported employment duration (as measured by the correlation coefficient) was moderate to high across all time periods for certain crops (e.g., r = 0.69-0.92 for apple-related work), by location (e.g., r = 0.76-0.95 for Washington State), and for agricultural work in general (r = 0.67-0.94), but was lower for specific tasks. Agreement of job counts was high for total work history for certain crops (e.g., r = 0.93 for apple-related work), by location (e.g., r = 0.90 for Washington State), and for agricultural work in general (r = 0.89), but paradoxically decreased with proximity to the interview date. Agreement of both measures tended to be highest for those tasks and crops in which subjects reported spending the most time. Categorization of subjects into tertiles on the basis of either cumulative duration or counts produced results similar to those observed for job counts. CONCLUSIONS: The icon-calendar questionnaire is an effective tool for estimating cumulative duration of certain work categorizations among subjects with complex work histories.

Comparison of a traditional questionnaire with an icon/calendar-based questionnaire to assess occupational history.

BACKGROUND: Self-reported work histories are an essential tool for estimating exposure in many occupational epidemiologic studies. However, the transience of some occupations such as farm work can hamper recall, resulting in inaccurate reporting. To address this problem, we have developed an icon/calendar-based questionnaire. This study compares work histories collected via this questionnaire to those collected via a traditional questionnaire. METHODS: Eighty-nine farmworkers and non-farmworkers were interviewed twice, 8-10 months apart, about their lifetime employment. In the first interview, subjects were asked to recount their entire work history, starting from the interview date and moving backwards in time ("traditional questionnaire"). In the second interview, subjects were first asked about important life events, which were recorded with icons on a calendar. They were then asked to recount their work history, which was recorded, job-by-job, on the calendar with icons ("icon-calendar questionnaire"). RESULTS: Number of jobs and amount of work time accounted for since first employment were significantly greater using the icon-calendar questionnaire than the traditional questionnaire, the disparity increasing with time from the date of interview. The ratio of number of jobs in the traditional questionnaire to number of jobs in the icon-calendar questionnaire decreased from 100.0% in the most recent time period to 0.0% in the earliest time period. While the percentage of time explained by employment remained relatively constant across time periods in the icon-calendar questionnaire, ranging from 86.3 to 98.9%, it rapidly decreased with time in the traditional questionnaire, from 77.9% in the most recent time period to 0.0% in the earliest time period. CONCLUSIONS: The icon-calendar questionnaire was more effective than the traditional questionnaire for obtaining complex work histories during interviews, producing a more complete picture of a person's work history.

Comparability of data obtained from migrant farmworkers and their spouses on occupational history.

BACKGROUND: Epidemiologic studies, particularly case-control studies, often rely on proxy respondents to provide information about subjects' occupational histories. The quality of proxy-reported information in occupational histories has never been evaluated for migrant farmworkers. METHODS: We compared occupational histories self-reported by 31 farmworkers with those reported by their wives. The work histories were obtained using an icon/calendar-based questionnaire that was designed to facilitate recall for migrant farmworkers, who typically have complex work histories. RESULTS: The work histories provided by proxy respondents contained 32% fewer jobs and accounted for 24% fewer years than the self-reported histories. Correlations for lifetime duration of employment in different types of jobs were moderate to good for general agricultural jobs in Washington (0.70) and apple-related jobs (0.65), which were held by virtually all of the farmworkers; correlations were moderate to poor for less common jobs and for specific types of tasks. Agreement was better after marriage than before, and for jobs held in the current year compared to other time frames. Overall, the ability of the spouses to provide occupational histories for farmworkers was within the range observed in studies involving other occupations and industries. CONCLUSIONS: In studies involving farmworkers, when study subjects cannot be interviewed, spouses can provide useful information on occupational histories. However, the information should be used only for more generalized exposure assessments; it is most appropriate for estimating cumulative duration of agricultural work, or recent work, by place or for common crops.

Parkinsonism and occupational exposure to pesticides.

OBJECTIVE: To examine the risk of parkinsonism related to lifetime occupational exposure to pesticides among a cohort of men, mostly orchardists, in Washington State. METHODS: All 310 subjects in this study had previously participated in a cohort study of men occupationally exposed to pesticides. Subjects were given a structured neurological examination and completed a self administered questionnaire which elicited detailed information on pesticide (insecticide, herbicide, and fungicide) use throughout their working careers. Demographic characteristics were also sought. Subjects had a mean age of 69.6 years (range 49-96, SD 8.1). There were 238 (76.8%) subjects who reported some occupational exposure to pesticides, whereas 72 (23.2%) reported none. Parkinsonism was defined by the presence of two or more of rest tremor, rigidity, bradykinesia, and impairment of postural reflexes in subjects not on antiparkinsonian medication, or the presence of at least one sign if they were on such medication. Parkinson's disease was not studied explicitly because of the difficulty in distinguishing it from other parkinsonian syndromes. A generalised linear model was used to estimate prevalence ratios (PRs) for parkinsonism relative to history of farming, pesticide use, and use of well water. RESULTS: A PR of 2.0 (95% confidence interval (95% CI) 1.0 to 4.2) was found for subjects in the highest tertile of years of exposure to pesticides; a similarly increased, non-significant, PR was found for the middle tertile (1.9 (95% CI 0.9 to 4.0)), although a trend test did not show a significant exposure-response relation. No increased risks were found associated with specific pesticides or pesticide classes, nor with a history of farming or use of well water. CONCLUSION: Parkinsonism may be associated with long term occupational exposure to pesticides, although no associations with specific pesticides could be detected. This finding is consistent with most of the publications on this topic.

An occupational risk survey of a refractory brick company in Ha Noi, Viet Nam.

Viet Nam has an increasing need for building materials, including refractory bricks. Little is known regarding the occupational hazards incurred in brick manufacturing. To determine the occupational health hazards posed by a refractory brick operation in Ha Noi, Viet Nam, a cross-sectional occupational risk survey was conducted, focusing on respirable dust hazards. It included an industrial hygiene walk-through and gravimetric dust analysis. Noise, heat, lack of head protection, and dust exposure were hazards identified at the brick-manufacturing site. Respiratory protection involved a three-layer cloth mask that had not been tested for efficacy. Silica dust exposure levels exceeded the Vietnamese permissible exposure level by almost fivefold based on gravimetric assessment and estimated silica content. This brick manufacturing site contains significant injury and respiratory illness hazards. Further investigations are necessary to begin to develop occupational safety measures at the site.

Hazardous pesticides in Central America.

Pesticides are an extensively documented occupational and environmental hazard in Central America. Yet, severe problems persist. Toxic pesticide use in the Region increased during 1985-1999. High exposure levels and ineffectiveness of personal protective equipment evidence the difficulties for risk reduction. Acute poisonings remain a severe problem. Delayed and/or long-lasting health effects include dermatoses, cancer, and genotoxic, neurotoxic, and respiratory effects. The use of hazardous pesticides persists through deficiencies in government-driven assessment and risk management; excessive focus on regional harmonization; short-term economic interests; strong links between industry and governments; aggressive marketing; weak trade unions; and failure of universities to reach decision makers. Regulation based on local data is lacking. An agreement of the Ministries of Health for restricting the most toxic pesticides in Central America has potential for progress. The most effective way to reduce risk is to greatly reduce pesticide use. Actions needed include development of multidisciplinary strategies for local studies on health and environmental impact of pesticides; development of sustainable nonchemical agricultural technologies; evaluation of interventions; extending and sharing of expertise within the Region; strengthening of unions and communities; and redefining the role of industry toward development of safer products, with responsible marketing and reliable information.

Biologically based pesticide dose estimates for children in an agricultural community.

Current pesticide health risk assessments in the United States require the characterization of aggregate exposure and cumulative risk in the setting of food tolerances. Biologic monitoring can aggregate exposures from all sources and routes, and can integrate exposures for chemicals with a common mechanism of action. Its value was demonstrated in a recent study of organophosphorus (OP) pesticide exposure among 109 children in an agricultural community in Washington State; 91 of the children had parents working in agriculture. We estimated individual OP pesticide doses from urinary metabolite concentrations with a deterministic steady state model, and compared them to toxicologic reference values. We evaluated doses by assuming that metabolites were attributable entirely to either azinphos-methyl or phosmet, the two OP pesticides used most frequently in the region. Creatinine-adjusted average dose estimates during the 6- to 8-week spraying season ranged from 0 to 36 microg/kg/day. For children whose parents worked in agriculture as either orchard applicators or as fieldworkers, 56% of the doses estimated for the spray season exceeded the U.S. Environmental Protection Agency (EPA) chronic dietary reference dose, and 19% exceeded the World Health Organization acceptable daily intake values for azinphos-methyl. The corresponding values for children whose parents did not work in agriculture were 44 and 22%, respectively. The percentage of children exceeding the relevant reference values for phosmet was substantially lower (< 10%). Single-day dose estimates ranged from 0 to 72 microg/kg/day, and 26% of these exceeded the EPA acute reference dose for azinphos-methyl. We also generated dose estimates by adjustment for total daily urine volume, and these estimates were consistently higher than the creatinine-adjusted estimates. None of the dose estimates exceeded the empirically derived no-observable-adverse-effect levels for these compounds. The study took place in an agricultural region during a period of active spraying, so the dose estimates for this population should not be considered representative of exposures in the general population. The findings indicate that children living in agricultural regions represent an important subpopulation for public health evaluation, and that their exposures fall within a range of regulatory concern. They also demonstrate that biologically based exposure measures can provide data for health risk evaluations in such populations.

Effectiveness of interventions in reducing pesticide overexposure and poisonings.

OBJECTIVE: The objective of this paper was to review the effectiveness of interventions to reduce pesticide overexposure and poisonings in worker populations. METHODS: We used the Cochrane Collaboration search strategy to search the following databases for articles that tested the effectiveness of interventions in reducing human pesticide exposure or poisonings: MEDLINE, EMBASE, and Occupational Safety and Health (NIOSHTC). Interventions considered included comparisons of pesticide application methods, pesticide mixing methods, worker education, biological monitoring programs, personal protective equipment (PPE) use, pesticide substitutions, and legislation. The outcomes of interest included biological monitoring measures or personal exposure monitoring indicating a reduction of pesticide exposure, observed increased use of PPE, reduction in lost workdays, and where possible, evidence of changes in pesticide poisoning rates as identified by registries and population surveys. Studies were reviewed in depth with special attention to size and study design. RESULTS: Most studies evaluated exposure during differing configurations of PPE or during different mixing or handling methods. Most studies were small field tests of protective equipment involving less than 20 workers. Some studies examined biological indices of exposure such as cholinesterase or urinary metabolites. Studies showed that PPE was effective in reducing exposure. No controlled studies were found that addressed reducing pesticide poisonings. CONCLUSIONS: Changes in application procedures, packaging, mixing, use of personal protective equipment, and biological monitoring reduced pesticide exposure under controlled conditions. Cholinesterase monitoring can identify workers with a higher risk of overexposure. Most techniques were not tested in actual worksite programs. Interventions should be examined for their ability to reduce pesticide overexposure in actual working populations. No controlled evaluations of large legislative initiatives were found.

Fumigant-related illnesses: Washington State's five-year experience.

OBJECTIVE: Exposure to fumigants may have severe or persistent health effects. Washington State's fumigant-related illnesses were reviewed to better understand the circumstances surrounding exposure and resultant health effects. METHODS: Fumigant-related illnesses reported to and investigated by the Washington State Department of Health were reviewed. Illnesses considered by Department of Health to be definitely, probably, or possibly related to pesticide exposure were then analyzed. RESULTS: From 1992-1996, 39 (3.3%) of 1192 definite, probable, or possible cases of pesticide-related illnesses involved exposures to fumigants. Fumigant exposures during this period were to aluminum phosphide (15), methyl bromide (12), metam-sodium (9), and zinc phosphide (3). Symptoms included respiratory problems and eye and/or skin irritation for the majority of exposures, and no deaths were reported. The nature of exposure for these cases included exposure to applicators (17), reentry into a fumigated structure (9), improper storage or disposal (6), reentry into treated agricultural fields (4), drift from treated fields (2), and other (1). CONCLUSIONS: Review of fumigant exposures should be used to prevent future events through continued enforcement of established regulations and training of applicators.

Organophosphate neuropathy due to methamidophos: biochemical and neurophysiological markers.

Neuropathy target esterase (NTE), the putative target enzyme for organophosphate induced delayed polyneuropathy (OPIDP), can be measured in lymphocytes but has rarely been assessed in acute human poisoning. Serum autoantibodies to nervous system proteins develop in hens poisoned with neuropathic insecticides and also have not been studied after human poisoning. Serial lymphocyte NTE (LNTE) was measured in a 16-year-old boy after acute poisoning with methamidophos for evaluation as a predictor of subsequent neuropathy. The profiles of serum autoantibodies to neurofilament triplet proteins, myelin basic protein, and glial fibrillary acidic protein were measured in order to characterize changes occurring as a result of OPIDP. Clinical neuropathy characterized by steppage gate and profound lower extremity weakness, decreased grip and pinch strength, and decreased ulnar and absent tibial compound muscle action potentials developed 2 weeks following poisoning. Sensory examination and nerve conduction studies were normal. On day 3 following poisoning LNTE was depressed (77% compared with subsequent baseline enzyme activity). Marked increases in serum immunoglobulin G (IgG) autoantibodies to glial fibrillary acidic protein and to neurofilament 200 were observed after the development of OPIDP. We conclude that inhibition of lymphocyte NTE is predictive of subsequent OPIDP. Serum autoantibody titers to nervous system proteins may be useful markers of neuropathy.

Longitudinal decline in measured firefighter single-breath diffusing capacity of carbon monoxide values. A respiratory surveillance dilemma.

Seattle firefighters participate in a voluntary annual medical surveillance program including measurements of ventilatory capacity (FVC and FEV1) and single-breath diffusing capacity of carbon monoxide (DLCO). From 1989 to 1996, average % predicted DLCO (Crapo) for all participating firefighters declined from 94.4% (95% confidence interval [CI]: 93.4% to 95.5%) to 87.3% (95% CI: 86.2% to 88.3%), with no significant change in average FVC or FEV1. A random-effects regression model based on data from 812 firefighters with at least two annual sets of DLCO measurements showed the expected associations between DLCO and age, height, gender, race, ventilatory capacity, and smoking. In addition, two important temporal changes were observed, including, for an average firefighter, a large mean decline in DLCO of -1.02 ml/min/mm Hg associated with year of measurement, and a relatively smaller decline of -0.006 ml/min/mm Hg associated with number of fires fought. Although the stability of ventilatory capacity over time is reassuring, the marked temporal decline in diffusing capacity among this population of firefighters raises issues of concern. Interpretation of the observed decline poses a dilemma in terms of the reliability and efficacy of diffusing capacity as a screening tool, in whether DLCO is subject to unacceptable technical variability or whether it might provide more sensitive detection of early adverse respiratory effects of smoke inhalation.

Neurophysiological function in farm workers exposed to organophosphate pesticides.

To investigate neurophysiological effects of low-level exposure to foliar organophosphate residues during one season among agricultural workers, the authors performed a cross-sectional study of 67 Hispanic farm workers and 68 age-, gender-, ethnicity-, and education-matched reference subjects. The neurophysiological examination included sensory and motor nerve conduction and neuromuscular junction testing. Erythrocyte cholinesterase activity was measured at the time of examination. No statistically significant neurophysiological differences between the exposed and reference groups were observed. Farm workers and reference subjects had similar sensory nerve latency and amplitude (sural), motor nerve conduction velocity (ulnar), and neuromuscular junction function (ulnar). No relationship between duration of exposure during the season and electrophysiological measures of nerve function was found. Exposure of farm workers to the low levels of organophosphate pesticides during one season experienced by farm workers in this study was not associated with impaired peripheral neurophysiological function.