Italian survey on human behaviour for inhalation exposure assessment

In order to support risk management in identifying effective mitigation measures, exposure assessment related to environmental pollution needs to integrate monitoring of pollution levels and control data with information on population behaviour and lifestyle. With this aim, a sample population survey was carried out in a Northern Italian city, collecting data on human behavioural factors influencing inhalation exposure. Questionnaires gathering data on dwelling characteristics, and weekly individual diaries on personal behaviour, such as places frequented and daily activities, were used. Data collection was carried out in two different seasons, spring-summer and fall-winter. A sample of 270 families, randomly selected from the municipal registry, was enrolled for each seasonal observation. The study allowed quantification of variability in human behaviour revealing seasonal variation and differences due to age and gender. Daily activity patterns were described and probability distributions of inhalation rates were obtained for all observed population groups. A probabilistic exposure model was developed and the resulting exposure distributions for the two seasonal periods were compared. Results confirm that exposure estimates are strongly biased if variability in human behaviour is not taken into account.     

Simulation of average energy expenditures and related inhalation rates for the U.S. population

Inhalation rates (rVe) for determining intakes of air pollutants generally must be estimated because it is difficult to make direct inhalation measurements in free-standing populations. The key to quantifying rVe is to estimate the oxygen consumption rate (rO2) required to sustain an individual’s total daily energy expenditure (TDEE) and then to convert rO2 to rVe using the ventilatory equivalent for oxygen (VQ). To estimate TDEEs for U.S. population cohorts, nonlinear equations that predict TDEE were developed using data derived from doubly labeled water metabolic studies involving 222 groups with a total of 6,027 subjects. Monte Carlo sampling of lognormally distributed body weights, VQ values, and error terms of the TDEE predictions were then used to simulate average TDEE and rVe for U.S. population cohorts. The maximum TDEE value for males was 13.5 MJ/day, which occurred within the 19–29 year age cohort, and for females it was 10.4 MJ/day at ages 18–19 years. Analyses of the relationship between the body mass index (BMI) and physical activity level (PAL?=?TDEE?÷?resting metabolic rate) showed that PAL is not very sensitive to changes in BMI. The highest daily inhalation rates for males and females were 17 and 13 m³/day, respectively, and estimated breathing rates for active (nonresting) hours were about a factor of two greater than for inactive (sleep/resting) periods. Finally, it was shown that efforts to control obesity in the USA have the potential for reducing inhalation rates due to the decreased oxygen/energy requirements of lower body weights.     

Indoor exposure to bioaerosol particles: levels and implications for inhalation dose rates in schoolchildren

Children spend most of their time inside schools and bioaerosol particles are part of their everyday environment. Although bioaerosol particles are considered to be a potential risk factor for various health concerns, information concerning the indoor exposures and inhalation doses is still limited. This study aimed (i) to quantify bacterial and fungal particles levels in indoor and outdoor air of public primary schools, (ii) to assess the influence of ambient air on bacteria and fungi presence indoors, and (iii) to estimate the inhalation dose rates for respective children (8–10 years old) in comparison with adult staff. Air samples were collected in 20 primary schools in a total of 71 classrooms during heating season with a microbiological air sampler. The results showed that indoor bacterial and fungal concentrations were higher than outdoor levels (p?<?0.05), which could be explained by differences in density of occupation, occupant’s activities, and inadequate ventilation. CO₂ levels were significantly correlated with indoor bacteria concentrations. Moreover, mean indoor bacteria concentrations were above national limit values in all the evaluated Porto primary schools, from two to nine times higher. Regarding fungi concentrations, indoor levels were above the reference value in 75% of the schools and overall indoor levels registered a 3-fold increase compared with outdoor values. Children had two times higher inhalation dose rates to bioaerosol particles when compared to adult individuals. Thus, due to their susceptibility, special attention should be given to educational settings in order to guarantee the children healthy development.     

Particle size distribution and particle size-related crystalline silica content in granite quarry dust

Previous studies indicate that the relationship between empirically derived particle counts, particle mass determinations, and particle size-related silica content are not constant within mines or across mine work tasks. To better understand the variability of particle size distributions and variations in silica content by particle size in a granite quarry, exposure surveys were conducted with side-by-side arrays of four closed face cassettes, four cyclones, four personal environmental monitors, and a real-time particle counter. In general, the proportion of silica increased as collected particulate size increased, but samples varied in an inconstant way. Significant differences in particle size distributions were seen depending on the extent of ventilation and the nature and activity of work performed. Such variability raises concerns about the adequacy of silica exposure assessments based on only limited numbers of samples or short-term samples.     

A stochastic differential equation for exposure yields a beta distribution

This paper presents a stochastic differential equation for exposure based on a modified version of the standard dilution ventilation equation. An equilibrium solution is obtained with the assumption that variability in the rate of change of concentration is proportional to the product of concentration and one minus concentration. Appropriate definitions for concentration are used to ensure a physically consistent model. The probability distribution for exposure that results is the standard beta distribution. This model is supported by several exposure data sets, which fit the beta distribution well. Issues regarding parameter estimation for the beta distribution, and application of the model are presented. Recommendations are made for simultaneously collecting contaminant generation rate information, ventilation rates, and time-dependent breathing-zone tracer concentrations, in addition to the exposure data.     

Distributions of serum lipoproteins in children by repeated measurements

Serum lipids and lipoproteins were measured three times over 6 years in a total-community study of children in Bogalusa, Louisiana. Interrelationships and changes in the distributions of serum lipoprotein cholesterol levels were examined in terms of variability and precision of the laboratory measurements. Although distributions of serum lipoprotein cholesterol variables shifted among the three surveys, precision increased markedly as indicated by a decrease in the coefficient of variation for measurement error for total cholesterol, alpha-lipoprotein cholesterol, and triglycerides between Year 1 and Year 4 and then stabilized. Pre-beta-lipoprotein cholesterol was the most difficult variable to measure. The range and magnitude of correlation coefficients between lipid and lipoprotein variables were very similar. Despite quality controls, efforts to standardize laboratory analyses, and adherence to protocols, fluctuations in distributions of lipids and lipoproteins occurred when the same population was restudied. Long-term studies for coronary artery disease prevention should include laboratory safeguards that help to distinguish modest population changes in serum lipids and lipoproteins from laboratory drift.     

Exposure assessment of trichloroethylene

This article reviews exposure information available for trichloroethylene (TCE) and assesses the magnitude of human exposure. The primary sources releasing TCE into the environment are metal cleaning and degreasing operations. Releases occur into all media but mostly into the air due to its volatility. It is also moderately soluble in water and can leach from soils into groundwater. TCE has commonly been found in ambient air, surface water, and groundwaters. The 1998 air levels in microg/m(3) across 115 monitors can be summarized as follows: range = 0.01-3.9, mean = 0.88. A California survey of large water utilities in 1984 found a median concentration of 3.0 microg/L. General population exposure to TCE occurs primarily by inhalation and water ingestion. Typical average daily intakes have been estimated as 11-33 microg/day for inhalation and 2-20 microg/day for ingestion. A small portion of the population is expected to have elevated exposures as a result of one or more of these pathways: inhalation exposures to workers involved in degreasing operations, ingestion and inhalation exposures occurring in homes with private wells located near disposal/contamination sites, and inhalation exposures to consumers using TCE products in areas of poor ventilation. More current and more extensive data on TCE levels in indoor air, water, and soil are needed to better characterize the distribution of background exposures in the general population and elevated exposures in special subpopulations.     

Modeled estimates of chlorpyrifos exposure and dose for the Minnesota and Arizona NHEXAS populations

This paper presents a probabilistic, multimedia, multipathway exposure model and assessment for chlorpyrifos developed as part of the National Human Exposure Assessment Survey (NHEXAS). The model was constructed using available information prior to completion of the NHEXAS study. It simulates the distribution of daily aggregate and pathway-specific chlorpyrifos absorbed dose in the general population of the State of Arizona (AZ) and in children aged 3-12 years residing in Minneapolis-St. Paul, Minnesota (MSP). Pathways included were inhalation of indoor and outdoor air, dietary ingestion, non-dietary ingestion of dust and soil, and dermal contact with dust and soil. Probability distributions for model input parameters were derived from the available literature, and input values were chosen to represent chlorpyrifos concentrations and demographics in AZ and MSP to the extent possible. When the NHEXAS AZ and MSP data become available, they can be compared to the distributions derived in this and other prototype modeling assessments to test the adequacy of this pre-NHEXAS model assessment. Although pathway-specific absorbed dose estimates differed between AZ and MSP due to differences in model inputs between simulated adults and children, the aggregate model results and general findings for simulated AZ and MSP populations were similar. The major route of chlorpyrifos intake was food ingestion, followed by indoor air inhalation. Two-stage Monte Carlo simulation was used to derive estimates of both inter-individual variability and uncertainty in the estimated distributions. The variability in the model results reflects the difference in activity patterns, exposure factors, and concentrations contacted by individuals during their daily activities. Based on the coefficient of variation, indoor air inhalation and dust ingestion were most variable relative to the mean, primarily because of variability in concentrations due to use or no-use of pesticides. Uncertainty analyses indicated a factor of 10-30 for uncertainty of model predictions of 10th, 50th, and 90th percentiles. The greatest source of uncertainty in the model stems from the definition of no household pesticide use as no use in the past year. Because chlorpyrifos persists in the residential environment for longer than a year, the modeled estimates are likely to be low. More information on pesticide usage and environmental concentrations measured at different post-application times is needed to refine and evaluate this and other pesticide exposure models.     

Influence of room geometry and ventilation rate on airflow and aerosol dispersion: implications for worker protection.

Knowledge of dispersion rates and patterns of radioactive aerosols and gases through workrooms is critical for understanding human exposure and for developing strategies for worker protection. The dispersion within rooms can be influenced by complex interactions between numerous variables, but especially ventilation design and room furnishings. For this study, dependence of airflow and aerosol dispersion on workroom geometry (furnishings) and ventilation rate were studied in an experimental room that was designed to approximate a plutonium laboratory. Three different configurations of simulated gloveboxes and two ventilation rates (approximately 6 and 12 air exchanges per hour) were studied. A sonic anemometer was used to measure airflow parameters including all three components of air velocity vectors and turbulence intensity distributions at multiple locations and heights. Aerosol dispersion rates and patterns were measured by releasing aerosols multiple times from six different locations. Aerosol particle concentrations resolved in time and space were measured using 16 multiplexed laser particle counters. Comparisons were made of air velocities, turbulence, and aerosol transport across different ventilation rates and room configurations. A strong influence of ventilation rate on aerosol dispersion rates and air velocity was found, and changes in room geometry had significant effects on aerosol dispersion rates and patterns. These results are important with regards to constant evaluation of placement of air sampling equipment, benchmarking numerical models of room airflow, and design of ventilation and room layouts with consideration of worker safety.     

The changing age distribution of prostate cancer in Canada

BACKGROUND: Prostate cancer incidence rates are still increasing steadily; mortality rates are levelling, possibly decreasing; and hospitalization rates for many diagnoses are decreasing. Our objective is to examine changes in age distributions of prostate cancer during these times of change. METHODS: Prostate cancer cases were derived from the Canadian Cancer Registry, prostate cancer deaths from Vital Statistics, hospitalizations from the Hospital Morbidity File. Age-standardized rates were calculated based on the 1991 Canadian population. A prevalence correction for incidence rates was calculated. RESULTS: Age-specific incidence rates increased until 1995 for all ages, but a superimposed peak (1991-94) was greatest between ages 60-79. After 1995, increases in incidence continued for the under-70 age groups. Prevalence correction indicated the greatest underestimation of incidence rates for the oldest ages, but was less in Canada than in the United States. Mortality rates increased until 1994, then levelled and slowly decreased; age-specific mortality rates showed the greatest increase for the oldest ages but the earliest downturn for younger age groups. While hospitalizations dropped drastically after 1991, this drop was confined to elderly men (70+). CONCLUSIONS: Dramatic changes in age distributions of prostate cancer incidence, mortality and hospitalizations altered age profiles of men with prostate cancer. This illustrated the changing nature of prostate cancer as a public health issue and has important implications for health care provision, e.g., the increased numbers of younger new patients have different needs from the increasing numbers of elderly long-term patients who now spend less time in hospital.     

Inspiratory flow rates during hard work when breathing through different respirator inhalation and exhalation resistances

There has been a long-standing debate regarding the adequacy of airflow rates used in respirator certification testing and whether these test flow rates underestimate actual values. This study investigated breath by breath inspiratory peak flow rate, minute ventilation, and instantaneous flow rates of eight young, healthy volunteers walking on a treadmill at 80-85% of maximal aerobic capacity until exhaustion while wearing an air-purifying respirator with one of eight combinations of inhalation and exhalation resistance. An analysis of variance was performed to identify differences among the eight conditions. Scheffe's post hoc analysis indicated which means differed. The group of conditions with the highest average value for each parameter was identified and considered to represent a worst-case scenario. Data was reported for these conditions. A Gaussian distribution was fit to the data and the 99.9% probability levels determined. The 99.9% probability level for the peak and instantaneous flow rates were 374 L/min and 336 L/min, respectively. The minute ventilation distribution was not Gaussian. Less than 1% of the recorded minute ventilations exceeded 135 L/min. Instantaneous flow rates exceeded the National Institute for Occupational Safety and Health's respirator test standards of 64, 85, and 100 L/min constant flow 91%, 87%, and 82% of the time, respectively. The recorded minute ventilations exceeded the 40 L/min minute ventilation test standard (for tests with a sinusoidal flow pattern) 100% of the time. This study showed that young, healthy respirator wearers generated peak flow rates, minute ventilations, and instantaneous flow rates that consistently exceeded current test standards. Their flow rates should be higher than those of a respirator wearer performing occupational work and could be considered upper limits. Testing respirators and respirator cartridges using a sinusoidal breathing pattern with a minute ventilation of 135 L/min (peak flow rate approximately 424 L/min) would encompass 99% of the recorded minute ventilations and 99.9% of the predicted peak and instantaneous flow rates from this study and would more accurately reflect human respiration during strenuous exercise.     

An assessment of the interindividual variability of internal dosimetry during multi-route exposure to drinking water contaminants

The objective of this study was to evaluate inter-individual variability in absorbed and internal doses after multi-route exposure to drinking water contaminants (DWC) in addition to the corresponding variability in equivalent volumes of ingested water, expressed as liter-equivalents (LEQ). A multi-route PBPK model described previously was used for computing the internal dose metrics in adults, neonates, children, the elderly and pregnant women following a multi-route exposure scenario to chloroform and to tri- and tetra-chloroethylene (TCE and PERC). This scenario included water ingestion as well as inhalation and dermal contact during a 30-min bathroom exposure. Monte Carlo simulations were performed and distributions of internal dose metrics were obtained. The ratio of each of the dose metrics for inhalation, dermal and multi-route exposures to the corresponding dose metrics for the ingestion of drinking water alone allowed computation of LEQ values. Mean BW-adjusted LEQ values based on absorbed doses were greater in neonates regardless of the contaminant considered (0.129-0.134 L/kg BW), but higher absolute LEQ values were obtained in average adults (3.6-4.1 L), elderly (3.7-4.2 L) and PW (4.1-5.6 L). LEQ values based on the parent compound's AUC were much greater than based on the absorbed dose, while the opposite was true based on metabolite-based dose metrics for chloroform and TCE, but not PERC. The consideration of the 95th percentile values of BW-adjusted LEQ did not significantly change the results suggesting a generally low intra-subpopulation variability during multi-route exposure. Overall, this study pointed out the dependency of the LEQ on the dose metrics, with consideration of both the subpopulation and DWC.     

Sources of variability in levels and exposure to trihalomethanes

In the framework of a cohort study of pregnant women conducted in Brittany (France), we assessed the exposure to trihalomethanes (THM) during pregnancy in a subset by evaluating (1) potential sources of variability in household THM levels; (2) the between- and within-subject variability in THM levels; (3) THM levels in swimming pools; and (4) the role of water-related habits on total THM uptake. We visited 109 women from the ongoing cohort study at home for an interview and collection of tap water from October to December 2004. Forty-three of them were re-contacted to obtain a second tap water sample in April-May 2005. We designed a questionnaire to collect individual information on source and amount of drinking water, frequency of showering, bathing, and swimming pool attendance, and household characteristics. We obtained 282 THM measurements, 152 specifically for the study and 130 from a regulatory agency. Personal information and environmental data were combined using two methodologies (method 1 using regulatory data and method 2 using our THM measurements) with a different set of assumptions. We calculated ingestion, showering, bathing, and swimming pool THM uptakes and added up those uptakes to calculate total THM uptake. Average THM levels from our measurements in October, November-December, and April-May were 61.3, 45.1, and 54.5 microg/l, respectively. Geographical variability was low and characteristics of the household did not influence THM levels. Within-subject variability in THM levels was three times higher than between-subject variability. Average THM level in swimming pools was 80.4 microg/l. Average water consumption during pregnancy was 1.9l/day. The source of the household drinking water was 90% bottled, 8% municipal, and 2% from other sources. Forty-seven per cent attended swimming pools during pregnancy. Using method 1, the geometric mean of total THM uptake was 0.93 microg/day. Showering contributed 64%, swimming in pools 23%, bathing 12%, and drinking water 1% to the total THM uptake. In a setting with low geographical variability and limited environmental measurements, individual data is highly relevant to determine personal THM exposure and uptake. In a population that mainly drinks bottled water (e.g., pregnant women), individual THM uptakes are dominated by inhalation and dermal absorption during, showering, swimming in pools, and bathing.     

Development of a Parametric Simulation Model for Forecasting Goal-Oriented Treatment Outcomes

BACKGROUND: Treatment-to-goal (TTG) analyses are frequently used to predict guideline-directed population control rates for drug therapies based on mean efficacy data. Nevertheless, estimates are commonly inaccurate because variability in efficacy is not considered. A new methodology was developed to improve TTG forecasting. METHODS: Patient-level blood pressure (BP) lowering data sets, designed to simulate clinical trial results, were generated for testing from three underlying distributions: normal, lognormal, and beta. To emulate real-world conditions where patient-level data are unavailable, two approaches were considered: parametric--simulated BP lowering data were generated using the mean and standard deviation of the test data sets; and point-estimate--BP lowering was uniformly assigned as the mean lowering. BP control (systolic BP < 140 and diastolic BP < 90 mmHg) was forecasted by subtracting values generated by these two methods from baseline BP values in untreated hypertensive patients (n = 2483) from the Third National Health and Nutrition Examination Survey. Estimated control rates were compared to analyses where the patient-level data sets were bootstrapped. RESULTS: We assumed mean (+/- SD) BP lowering of 20 (12) mmHg systolic and 14 (7) mmHg diastolic. Parametric method predicted a BP control rate of 66.9% [95% confidence interval (CI) 65.7-67.9], similar to the bootstrapping approach (67.3%, 95% CI 65.9-68.8). The control rate projected based on the point-estimate method was 75.5%. The point-estimate method frequently led to substantially different results under a wide range of model assumptions. CONCLUSIONS: A new parametric-based forecasting method, which addresses underlying variability, improves on estimates based on mean efficacy only. In the absence of patient-level data, this method is generalizable to different therapeutic areas.     

中国居民经食物摄入和空气吸入微纳塑料暴露特征分析

  目的  分析中国居民经食物摄入和空气吸入微纳塑料(micro- and nanoplastics, MNPs)暴露特征。  方法  使用关键词检索PubMed、Web of Science、Scopus、中国知网和万方数据知识服务平台等国内外数据库,建立数据集,结合中国人群食物消费量和人体呼吸参数,计算中国居民经食物摄入和空气吸入的MNPs暴露量,与国外数据比较分析其MNPs暴露特征。  结果  分析来自28篇研究的4 511个样本数据显示,中国居民每年摄入约187 000~328 000个MNPs,考虑空气吸入,每年MNPs暴露量为192 000~335 000个MNPs,均高于美国居民暴露量。男性成年人MNPs摄入量最高。生活饮用水、海产品、瓶装水和空气是中国居民每日主要MNPs暴露源。中国居民经食物摄入MNPs类型以聚乙烯、聚丙烯和聚对苯二甲酸乙二酯为主,而经空气吸入MNPs类型以聚对苯二甲酸乙二酯、尼龙和聚丙烯腈为主。  结论  相比于美国居民,中国居民具有更高的MNPs暴露风险,削减饮用水和海产品中MNPs含量,可有效降低中国居民MNPs暴露风险。     

An analysis of risk from exposure to aldicarb using immune response of nonuniform populations of mice

The immunomodulation response of mice to low levels of aldicarb in drinking water was investigated in four series of studies. The splenic plaque forming cell (PFC) response to red sheep cells were measured for treatment levels of 0.01 to 1,000 ppb (g/kg). Based on their beginning and end body weights, the animal populations were uniform in all series of tests, but based on their net body weights and PFC counts they were highly nonuniform in the 30 and 60 day tests and uniform in the 90 and 180 day tests.The mean PFC counts for animals in each treatment were calculated and compared with the mean PFC counts for animals in the controls in all four series of tests. This approach ignores the variability and nonuniformity in the animal population. The outcomes using this approach were stimulatory for the 30 and 60 day tests and inhibitory for the 90 and 180 day tests.An alternative approach was developed based on the analysis of the distributions of the relative PFC counts of each animal in a treatment with each animal in a control, and specifically addresses the variability and nonuniformity in animal population as integral parts of the analysis. The distribution peaks were estimated by maximum likelihood and kernel/bootstrap procedures and were used to summarize the tests. The outcomes were consistently inhibitory, indicating immune suppression. The outcome of this approach converged to the outcome of the mean PFC approach for the 90 and 180 day tests where the animal populations were uniform.     

Fate of the inhaled smoke particles from fire scenes in the nasal airway of a realistic firefighter: A simulation study

Understanding the inhalation, transport and deposition of smoke particles during fire missions are important to evaluating the health risks for firefighters. In this study, measurements from Underwriters Laboratories' large-scale fire experiments on smoke particle size distribution and concentration in three residential fire scenes were incorporated into models to investigate the fate of inhaled toxic ultrafine particulates in a realistic firefighter nasal cavity model. Deposition equations were developed, and the actual particle dosimetry (in mass, number and surface area) was evaluated. A strong monotonic growth of nasal airway dosages of simulated smoke particles was identified for airflow rates and fire duration across all simulated residential fire scene conditions. Even though the “number” dosage of arsenic in the limited ventilation living room fire was similar to the “number” dosage of chromium in the living room, particle mass and surface area dosages simulated in the limited living room were 90–200 fold higher than that in the ventilated living room. These were also confirmed when comparing the dosimetry in the living room and the kitchen. This phenomenon implied that particles with larger size were the dominant factors in mass and surface area dosages. Firefighters should not remove the self-contained breathing apparatus (SCBA) during fire suppression and overhaul operations, especially in smoldering fires with limited ventilation.     

Variability in biological monitoring of solvent exposure. I. Development of a population physiological model

Biological indicators of exposure to solvents are often characterised by a high variability that may be due either to fluctuations in exposure or individual differences in the workers. To describe and understand this variability better a physiological model for differing workers under variable industrial environments has been developed. Standard statistical distributions are used to simulate variability in exposure concentration, physical workload, body build, liver function, and renal clearance. For groups of workers exposed daily, the model calculates air monitoring indicators and biological monitoring results (expired air, blood, and urine). The results obtained are discussed and compared with measured data, both physiological (body build, cardiac output, alveolar ventilation) and toxicokinetic for six solvents: 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, benzene, toluene, styrene, and their main metabolites. Possible applications of this population physiological model are presented.     

Interpersonal and temporal variability of urinary cotinine in elderly subjects

Although a single measurement of urinary cotinine is often used for biological monitoring, the validity of this measurement for estimating long-term exposure has not been well evaluated. The purpose of this study was to determine the efficacy of using a single measurement per person to estimate long-term smoking exposure in an elderly population. Analysis was conducted using a cohort of elderly subjects for whom multiple urinary cotinine measurements had been collected over eight weeks. The mixed-effects model of urinary cotinine indicated that interpersonal variability was greater than temporal variability. The efficacy of using single measurements to track the mean long-term exposure of a population is supported by the relatively consistent population averages. The classification of high and low exposure groups using a single measurement or using eight measurements produced similar group distributions. When using cut-off levels of 20 and 100 μg cotinine/g creatinine, 9.3% and 5.6% of individual exposures were misclassified, respectively, when using a single measurement. Urinary cotinine can be a useful biomarker for characterizing exposure to tobacco smoke. Although the incidence of misclassification decreased with an increase in the number of measurements, a single measurement of the urinary cotinine level may accurately represent long-term exposure to tobacco smoke.     

Determination of potential dermal and inhalation operator exposure to malathion in greenhouses with the whole body dosimetry method

One of the steps during the authorization process of plant protection products (PPP) in the European Union is to evaluate the safety of the operator. For this purpose, information on the probable levels of operator exposure during the proposed uses of the PPP is required. These levels can be estimated by using existing mathematical models or from field study data. However, the existing models have several shortcomings, including the lack of data for operator exposure levels during spray applications by hand lance, especially in greenhouses. The present study monitored the potential dermal and inhalation operator exposure from hand-held lance applications of malathion on greenhouse tomatoes at low and high spraying pressures. The methodology for monitoring potential exposure was based on the whole body dosimetry method. Inhalation exposure was monitored using personal air pumps and XAD-2 sampling tubes. For the monitoring of hand exposure, cotton gloves were used in two trials and rubber gloves in another three. The total volumes of spray solution contaminating the body of the operator were 25.37 and 35.83 ml/h, corresponding to 0.05 and 0.07% of the applied spray solution, respectively, in the case of low pressure knapsack applications and from 160.76 to 283.45 ml/h, corresponding to 0.09-0.19% of the spray solution applied, in the case of hand lance applications with tractor-generated high pressure. Counts on gloves depended on the absorbance/repellency of the glove material. The potential inhalation exposures were estimated at 0.07 and 0.09 ml/h in the case of low pressure knapsack applications, based on a ventilation rate of 25 l/min. Both potential dermal operator exposure (excluding hands) and potential inhalation exposure were increased by a factor of approximately 7 when the application pressure was increased from 3 to 18 bar in greenhouse trials with a tractor-assisted hand lance, the rest of the application conditions being very similar.