Inhalation and dermal exposure to biocidal products during foam and spray applications

OBJECTIVES

Foaming and spraying are common application techniques for biocidal products. In the past, inhalation and dermal exposure during spraying have been investigated extensively. Currently, however, no exposure data are available for foaming, hindering a reliable risk assessment for foam applications of biocidal products. The focus of this project was the quantification of inhalation and potential dermal exposure to non-volatile active substances during the foam application of biocidal products in occupational settings. In some settings, exposure during spray application was measured for comparative purposes.

METHODS

The inhalation and dermal exposure of operators were investigated during the application of benzalkonium chlorides and pyrethroids by foaming and spraying, considering both small- and large-scale application devices. Inhalation exposure was measured by personal air sampling; potential dermal exposure was measured using coveralls and gloves.

RESULTS

Potential dermal exposure was substantially higher than inhalation exposure. Changing from spraying to foaming reduced inhalation exposure to airborne non-volatile active substances, but had no relevant effect on potential dermal exposure. However, for potential dermal exposure, considerable differences were observed between the application device categories.

CONCLUSIONS

To our knowledge, this study presents the first comparative exposure data for the foam and spray application of biocidal products in occupational settings with detailed contextual information. The results indicate a reduction of inhalation exposure with foam application compared to spray application. However, special attention is necessary for dermal exposure, which is not reduced by this intervention.

Aerosol formation during foam application of non-volatile biocidal substances

The application of biocidal products by foam is considered an alternative to droplet spraying when disinfecting surfaces or fighting infestations. Inhalation exposure to aerosols containing the biocidal substances cannot be ruled out during foaming. In contrast to droplet spraying, very little is known about aerosol source strength during foaming. In this study, the formation of inhalable aerosols was quantified according to the aerosol release fractions of the active substance. The aerosol release fraction is defined as the mass of active substance transferred into inhalable airborne particles during foaming, normalised to the total amount of active substance released through the foam nozzle. Aerosol release fractions were measured in control chamber experiments where common foaming technologies were operated according to their typical conditions of use. These investigations include foams generated mechanically by actively mixing air with a foaming liquid as well as systems that use a blowing agent for foam formation. The values of the aerosol release fraction ranged from 3.4 × 10-6 to 5.7 × 10-3 (average values). For foaming processes based on mixing air and the foaming liquid, the release fractions could be correlated to the process and foam parameters such as foam exit velocity, nozzle dimensions, and foam expansion ratio.

Prediction of Dermal Exposure to Chemical Substances Using a Fluorescence Method within the SysDEA Project

Dermal exposure is an important exposure route for occupational exposure and risk assessment. A fluorescence method has been developed to quantify occupational dermal exposure based on a visualization technique, using Tinopal SWN as a fluorescent tracer. The method was developed within the framework of a large experimental study, the SysDEA project. In SysDEA, dermal exposure was measured with different methods for 10 simulated exposure situations by sampling powder and liquid formulations containing Tinopal SWN on coveralls and patches and subsequently chemically analysing them. For the fluorescence method, photographs of exposed volunteers who performed the experiments were taken inside a room which consisted of an optimized arrangement of several UV irradiating tube light brackets, reflective and non-reflective backgrounds for maximum light diffusion and a camera. Image processing analysis software processed these photographs to obtain corresponding light intensity in terms of summed pixel values. To be able to estimate the amount of Tinopal SWN, 25% of the measured data from the SysDEA experiments were used to calibrate by correlating the summed pixel values from the photographs to actual measured exposure values using a second order regression model. For spraying both high and low viscosity liquids, showing uniformly distributed exposure patterns, strong Pearson correlation coefficients (R > 0.77) were observed. In contrast, the correlations were either inconsistently poor (R = -0.17 to 0.28 for pouring, rolling high viscosity liquid, manually handling objects immersed in low viscosity liquid and handling objects contaminated with powder), moderate (R = 0.73 for dumping of powder), or strong (R = 0.83 and 0.77 for rolling low viscosity liquid and manually handling objects immersed in high viscosity liquid). A model for spraying was developed and calibrated using 25% of the available experimental data for spraying and validated using the remaining 75%. Under given experimental conditions, the fluorescence method shows promising results and can be used for the quantification of dermal exposure for different body parts (excluding hands) for spraying-like scenarios that have a more uniform exposure pattern, but more research is needed for exposure scenarios with less uniform exposure patterns. For the estimation of exposure levels, the surface loading limit should be lower than 1.5░µg/cm2 (a lower limit could not be quantified based on experiments conducted in this study) on a large surface, like a coverall, which should be ideally perpendicular to the camera.

Inhalation and dermal exposure of workers during timber impregnation with creosote and subsequent processing of impregnated wood

OBJECTIVES

Coal tar creosote oils are used as highly effective wood protectants for, e.g., railway sleepers, utility poles and marine pilings. For impregnation of wood, the hot creosote oil is mostly applied in vacuum processes and by hot-and-cold dipping. From the perspective of an occupational hygienist, creosote tar oils are problematic because they have a number of hazardous properties, including carcinogenicity. We have studied inhalation and dermal exposure in six and four impregnation plants, respectively, in Germany. Some plants were visited repeatedly, for up to five measurement campaigns conducted over several years. Inhalation and dermal exposure resulting from vacuum impregnation and from hot-and-cold dipping, as well as secondary exposure resulting from assembly of impregnated railway sleepers have been measured. Accompanying, human biomonitoring of the employees has been performed.

METHODS

Inhalation exposure was measured using personal air samplers, collecting particles and vapours simultaneously. Dermal exposure was investigated by whole body dosimetry using disposable chemical protective coveralls and split leather gloves. 18 polycyclic aromatic hydrocarbons (PAHs) have been determined separately by high performance liquid chromatography (HPLC) or gas chromatography-mass spectrometry (GC-MS), respectively. For human biomonitoring 1-hydroxypyrene (1-OHP) in urine related to creatinine has been measured using HPLC. Both, pre- and post-shift values have been determined for this metabolite.

RESULTS

Dermal exposure towards pyrene and the sum of the determined 18 PAHs as well as inhalation exposure to naphthalene, pyrene and the sum of the determined 18 PAHs are presented in this paper. The plants performing vacuum impregnation have employed different constructive, technical and organisational measures, and some measures have also changed between the different measurement campaigns. We have found that cooling the vacuum impregnation vessel before unloading can reduce inhalation exposure to about one-third. However, our data shows that installation of structural or technical risk management measures (RMM) did not always reduce the exposure as intended, and can even lead to increased exposure in adverse constellations. Dermal exposure was strongly affected by differences in the working procedures. Measurements performed during assembly of impregnated railway sleepers indicate that secondary exposure leads to lower inhalation, but similar dermal exposure compared to the impregnation processes. Also 1-OHP excretion rates are similar after impregnation process and after assembly of impregnated railway sleepers.

CONCLUSION

Our recent data underlines that efficient reduction of the exposure resulting from impregnation with creosote requires sophisticated risk reduction strategies. Structural measures such as the enclosure of the loading area and technical measures like local exhaust ventilation shall be coordinated carefully with organisational measures and provision of personal protective equipment. The data presented here represents a broad bandwidth of current workplace situations in the creosote oil processing industry and is therefore suitable for risk assessment in related plants as well as under regulatory frameworks like the European Biocides Regulation. Each plant in this investigation was unique. Together they represent the whole width of this branch in Germany. Additionally, the number of plants and exposed workers is limited and relative low. Therefore, a comprehensive consideration and statistical analysis were not feasible.

Comparison of Measurement Methods for Dermal Exposure to Hazardous Chemicals at the Workplace: The SysDEA Project

There is a principal need for more precise methodology with regard to the determination of occupational dermal exposure. The goal of the Systematic analysis of Dermal Exposure to hazardous chemical Agents at the workplace project was therefore to generate scientific knowledge to improve and standardize measurement methods for dermal exposure to chemicals at the workplace. In addition, the comparability of different measurement methods was investigated. Different methods (body sampling by means of coveralls and patches, hand sampling by means of gloves and washing, and head sampling by means of headbands and wiping) were compared. Volunteers repeatedly performed a selection of tasks under standardized conditions in test chambers to increase the reproducibility and decrease variability. The selected tasks were pouring, rolling, spraying, and handling of objects immersed in liquid formulations, as well as dumping and handling objects contaminated with powder. For the chemical analysis, the surrogate test substance Tinopal SWN was analyzed by means of a high-performance liquid chromatographic method using a fluorescence detector. Tinopal SWN was either applied as a solid product in its pure form, or as a low and high viscosity liquid containing Tinopal SWN in dissolved form. To compare the sampling methods with patches and coveralls, the exposure values as measured on the patches were extrapolated to the surface areas of the respective parts of the coverall. Based on this extrapolation approach, using the patch method resulted in somewhat higher exposure values compared to using a coverall for all exposure situations, but the differences were only statistically significant in case of the liquid exposure situations. Using gloves resulted in significantly higher exposure values compared to hand wash for handling immersed objects, rolling, and handling contaminated objects, and slightly higher (not significant) exposure values during pouring and spraying. In the same context, applying wipe sampling resulted in higher exposure values than using a headband, which was at least partly due to extrapolation of the wipe results to the surface area of the headband. No ‘golden standard’ with regard to a preferred measurement method for dermal exposure could be identified from the methods as investigated in the current study.

How safe is control banding? Integrated evaluation by comparing OELs with measurement data and using monte carlo simulation

The present study aims to explore the protection level that can be achieved by the German control banding (CB) tool Einfaches Massnahmenkonzept Gefahrstoffe, 'Easy-to-use workplace control scheme for hazardous substances'. The rationale of our integrated approach is based on the Bewertungsindex (BWI), which is the quotient of the exposure level and the occupational exposure limit (OEL), with BWI <1 indicating compliance. The frequency distributions of the BWI were calculated in order to reflect statistically the variability of workplace conditions. The corresponding statistical values of the frequency distributions (percentiles etc.) are interpreted as an indicator of the level of protection that is achieved. The occupational exposure data sets used in the calculation of the BWI frequency distribution were mainly collected from Bundesanstalt für Arbeitsschutz und Arbeitsmedizin field studies. The data sets taken into account were selected according to the criteria 'hazard band, exposure potential, control approach'. Such a combination is called the 'control banding scenario' (CBS). Measurement data are only available for two CBS: in the case of the CBS 'hazard band A, EPL3, CS1' the only data that are available (n = 220) relate to propane-2-ol as used in the area of offset printing. Only 0.4 % of the BWI are above 1, this indicating a high level of compliance. In the case of the CBS 'Hazard band B, EPL2, CS1', exposure data are available from screen-printing firms (n = 50), optician workshops (n = 49), and from the area of furniture production (n = 13). The frequency distributions of the BWI reveal almost no instances of values being exceeded in the three branches. In a subsequent step, a Monte Carlo Simulation was employed to explore whether the BWI frequency distributions can be generalized using a probabilistic model. The frequency distributions of the exposure levels and the OELs were used as the input data for the model. The simulation results show that the model distribution, called Modellierter Bewertungsindex distribution, can reproduce the BWI distribution if the data basis is homogeneous (data from one branch) and less correlated. In case of a heterogeneous data set (pooled data from different branches), the simulation results can be interpreted as generic statements about the attainable protection level. It was found that CB does not (at least potentially) guarantee compliance in either case. On the other hand, the generic simulation showed that compliance was high for volatile liquids used in closed systems (CBS: 'hazard band C, EPL3, CS3') and for solids in the presence of local exhaust ventilation (CBS: 'hazard band B, EPS3, CS2').

Evaluation of the HSE COSHH Essentials exposure predictive model on the basis of BAuA field studies and existing substances exposure data

This paper presents an in-house BAuA study on the evaluation of the COSHH Essentials exposure predictive model. External validation is based on measurement data obtained in BAuA field studies performed in various industries, e.g. printing industry and textile industry. In addition, measurement data and information on industrial hygiene provided by the chemical industry within the framework of the Existing Substances Risk Assessment programme are used. Although the evaluated exposure data cover a wide variety of activities and workplace scenarios, there is still a considerable lack of appropriate exposure data, especially for the more stringent control strategies. It was found that the level of agreement between the measurements for solid substances (powders, dusts) and the predicted ranges is reasonably good. The situation is in part different for liquids. In workplaces where organic solvents are used in litre quantities, exposure levels are within the predicted ranges or are often lower. For small-scale uses of liquids (millilitre scale), e.g. in carpenters' workshops, there were indications that the exposure levels can exceed the predicted ranges. However, it must be noted that the database is rather small.