Exposure assessment: the influence of environmental monitoring methodology

Exposure assessment is an important step of risk assessment process and has evolved more quickly than perhaps any aspect of the four-step risk paradigm (hazard identification, exposure assessment, dose-response analysis, and risk characterization). Nevertheless, some epidemiological studies have associated adverse health effects to a chemical exposure with an inadequate or absent exposure quantification. In addition to the metric used, the truly representation of exposure by measurements depends on: the strategy of sampling, random collection of measurements, and similarity between the measured and unmeasured exposure groups. Two environmental monitoring methodologies for formaldehyde occupational exposure were used to assess the influence of metric selection in exposure assessment and, consequently, in risk assessment process.

Monitoring exposure to airborne ultrafine particles in Lisbon, Portugal

The aim of this study is to contribute to the assessment of exposure levels of ultrafine particles (UFP) in the urban environment of Lisbon, Portugal, due to automobile traffic, by monitoring lung-deposited alveolar surface area (resulting from exposure to UFP) in a major avenue leading to the town centre during late Spring, as well as in indoor buildings facing it. This study revealed differentiated patterns for week days and weekends, consistent with PM(2.5) and PM(10) patterns currently monitored by air quality stations in Lisbon. The observed ultrafine particulate levels could be directly related with the fluxes of automobile traffic. During a typical week, UFP alveolar deposited surface area varied between 35.0 and 89.2 µm(2)/cm(3), which is comparable with levels reported for other towns such in Germany and United States. The measured values allowed the determination of the number of UFP per cm(3), which are comparable to levels reported for Madrid and Brisbane. In what concerns outdoor/indoor levels, we observed higher levels (32-63%) outdoor, which is somewhat lower than levels observed in houses in Ontario.

Monitoring exposure to airborne ultrafine particles in Lisbon, Portugal

The aim of this study is to contribute to the assessment of exposure levels of ultrafine particles (UFP) in the urban environment of Lisbon, Portugal, due to automobile traffic, by monitoring lung-deposited alveolar surface area (resulting from exposure to UFP) in a major avenue leading to the town centre during late Spring, as well as in indoor buildings facing it. This study revealed differentiated patterns for week days and weekends, consistent with PM2.5 and PM10 patterns currently monitored by air quality stations in Lisbon. The observed ultrafine particulate levels could be directly related with the fluxes of automobile traffic. During a typical week, UFP alveolar deposited surface area varied between 35.0 and 89.2 mu m(2)/cm(3), which is comparable with levels reported for other towns such in Germany and United States. The measured values allowed the determination of the number of UFP per cm(3), which are comparable to levels reported for Madrid and Brisbane. In what concerns outdoor/indoor levels, we observed higher levels (32-63%) outdoor, which is somewhat lower than levels observed in houses in Ontario.

Occupational exposure to formaldehyde: effects of years of exposure in the frequency of micronucleus

Formaldehyde: an important industrial compound used in the manufacture of synthetic resins and chemical compounds such as lubricants and adhesives; also applied as a disinfectant, preservative and in cosmetics productions; relevant workplace exposure to FA also occurs in anatomy, pathology and in mortuaries; classified by IARC as carcinogenic to humans (Group 1), based on sufficient evidence in humans and experimental animals; manifold in vitro studies indicated that FA can induce genotoxic effects in proliferating cultured mammalian cells. Aim of the study: to evaluate if years of exposure induced a genotoxic biomarkers increase, namely MN in lymphocytes and buccal cells, in workers occupationally exposed to FA (factory and pathology anatomy laboratory).

On the assessment of exposure to airborne ultrafine particles in urban environments

The aim of this study was to contribute to the assessment of exposure levels of ultrafine particles in the urban environment of Lisbon, Portugal, due to automobile traffic, by monitoring lung deposited alveolar surface area (resulting from exposure to ultrafine particles) in a major avenue leading to the town center during late spring, as well as in indoor buildings facing it. Data revealed differentiated patterns for week days and weekends, consistent with PM2.5 and PM10 patterns currently monitored by air quality stations in Lisbon. The observed ultrafine particulate levels may be directly correlated with fluxes in automobile traffic. During a typical week, amounts of ultrafine particles per alveolar deposited surface area varied between 35 and 89.2 μm2/cm3, which are comparable with levels reported for other towns in Germany and the United States. The measured values allowed for determination of the number of ultrafine particles per cubic centimeter, which are comparable to levels reported for Madrid and Brisbane. In what concerns outdoor/indoor levels, we observed higher levels (32 to 63%) outdoors, which is somewhat lower than levels observed in houses in Ontario.

Biological monitoring of aflatoxin (AFB1) in workers of swine and poultry production

Although a great body of literature exists concerning the ingestion of food contaminated with aflatoxin, there are still few studies regarding mycotoxin inhalation in occupational settings. Since mycotoxins are relatively non-volatile, inhalation exposure is cause by inhalation of airborne fungal particulates or fungi-contaminated substrates that contain aflatoxin. We intend to know if there is occupational exposure to aflatoxin in Portuguese poultry and swine production. A total of 19 individuals (11 swine; 8 poultry) agreed and provided blood samples during the course of this investigation. Measurement of AFB1 was performed by ELISA. The samples were treated with pronase (Merck), wash in a Column C18 and purification was made with immunoaffinity columns (R.biopharma), specific for AFB1. It was applied statistical test (Mann-Whitney) to verified statistical difference in AFB1 results between the two settings. Results varied with concentrations from exposure. Only women’s in both settings have results Exposure to air and dust containing aflatoxin by inhalation should be consider a route of exposure in both settings.

Exposure and genotoxicity assessment methodologies: the case of formaldehyde occupational exposure

Formaldehyde (FA) ranks 25th in the overall U.S. chemical production, with more than 5 million tons produced each year. Given its economic importance and widespread use, many people are exposed to FA occupationally. Recently, based on the correlation with nasopharyngeal cancer in humans, the International Agency for Research on Cancer (IARC) confirmed the classification of FA as a Group I substance. Considering the epidemiological evidence of a potential association with leukemia, the IARC has concluded that FA can cause this lymphoproliferative disorder. Our group has developed a method to assess the exposure and genotoxicity effects of FA in two different occupational settings, namely FAbased resins production and pathology and anatomy laboratories. For exposure assessment we applied simultaneously two different techniques of air monitoring: NIOSH Method 2541 and Photo Ionization Detection Equipment with simultaneously video recording. Genotoxicity effects were measured by cytokinesis-blocked micronucleus assay in peripheral blood lymphocytes and by micronucleus test in exfoliated oral cavity epithelial cells, both considered target cells. The two exposure assessment techniques show that in the two occupational settings peak exposures are still occurring. There was a statistical significant increase in the micronucleus mean of epithelial cells and peripheral lymphocytes of exposed individuals compared with controls. In conclusion, the exposure and genotoxicity effects assessment methodologies developed by us allowed to determine that these two occupational settings promote exposure to high peak FA concentrations and an increase in the micronucleus mean of exposed workers. Moreover, the developed techniques showed promising results and could be used to confirm and extend the results obtained by the analytical techniques currently available.

Exposure to particles and fungi in Portuguese swine production

Versão preprint.

Genotoxic effects in occupational exposure to formaldehyde: A study in anatomy and pathology laboratories and formaldehyde-resins production

Background - According to the Report on Carcinogens, formaldehyde ranks 25th in the overall U.S. chemical production, with more than 5 million tons produced each year. Given its economic importance and widespread use, many people are exposed to formaldehyde environmentally and/or occupationally. Presently, the International Agency for Research on Cancer classifies formaldehyde as carcinogenic to humans (Group 1), based on sufficient evidence in humans and in experimental animals. Manyfold in vitro studies clearly indicated that formaldehyde can induce genotoxic effects in proliferating cultured mammalian cells. Furthermore, some in vivo studies have found changes in epithelial cells and in peripheral blood lymphocytes related to formaldehyde exposure. Methods - A study was carried out in Portugal, using 80 workers occupationally exposed to formaldehyde vapours: 30 workers from formaldehyde and formaldehyde-based resins production factory and 50 from 10 pathology and anatomy laboratories. A control group of 85 non-exposed subjects was considered. Exposure assessment was performed by applying simultaneously two techniques of air monitoring: NIOSH Method 2541 and Photo Ionization Detection equipment with simultaneously video recording. Evaluation of genotoxic effects was performed by application of micronucleus test in exfoliated epithelial cells from buccal mucosa and peripheral blood lymphocytes. Results - Time-weighted average concentrations not exceeded the reference value (0.75 ppm) in the two occupational settings studied. Ceiling concentrations, on the other hand, were higher than reference value (0.3 ppm) in both. The frequency of micronucleus in peripheral blood lymphocytes and in epithelial cells was significantly higher in both exposed groups than in the control group (p < 0.001). Moreover, the frequency of micronucleus in peripheral blood lymphocytes was significantly higher in the laboratories group than in the factory workers (p < 0.05). A moderate positive correlation was found between duration of occupational exposure to formaldehyde (years of exposure) and micronucleus frequency in peripheral blood lymphocytes (r = 0.401; p < 0.001) and in epithelial cells (r = 0.209; p < 0.01). Conclusions - The population studied is exposed to high peak concentrations of formaldehyde with a long-term exposure. These two aspects, cumulatively, can be the cause of the observed genotoxic endpoint effects. The association of these cytogenetic effects with formaldehyde exposure gives important information to risk assessment process and may also be used to assess health risks for exposed workers.

Task-based occupational exposure assessment and particle number concentration: two important data resources to perform risk assessment for occupational exposure to particles

Environment monitoring has an important role in occupational exposure assessment. However, due to several factors is done with insufficient frequency and normally don´t give the necessary information to choose the most adequate safety measures to avoid or control exposure. Identifying all the tasks developed in each workplace and conducting a task-based exposure assessment help to refine the exposure characterization and reduce assessment errors. A task-based assessment can provide also a better evaluation of exposure variability, instead of assessing personal exposures using continuous 8-hour time weighted average measurements. Health effects related with exposure to particles have mainly been investigated with mass-measuring instruments or gravimetric analysis. However, more recently, there are some studies that support that size distribution and particle number concentration may have advantages over particle mass concentration for assessing the health effects of airborne particles. Several exposure assessments were performed in different occupational settings (bakery, grill house, cork industry and horse stable) and were applied these two resources: task-based exposure assessment and particle number concentration by size. The results showed interesting results: task-based approach applied permitted to identify the tasks with higher exposure to the smaller particles (0.3 μm) in the different occupational settings. The data obtained allow more concrete and effective risk assessment and the identification of priorities for safety investments.

On the assessment of exposure to airborne ultrafine particles in urban environments

The aim of this study was to contribute to the assessment of exposure levels of ultrafine particles in the urban environment of Lisbon, Portugal, due to automobile traffic, by monitoring lung deposited alveolar surface area (resulting from exposure to ultrafine particles) in a major avenue leading to the town center during late spring, as well as in indoor buildings facing it. Data revealed differentiated patterns for week days and weekends, consistent with PM2.5 and PM10 patterns currently monitored by air quality stations in Lisbon. The observed ultrafine particulate levels may be directly correlated with fluxes in automobile traffic. During a typical week, amounts of ultrafine particles per alveolar deposited surface area varied between 35 and 89.2 mu m2/cm3, which are comparable with levels reported for other towns in Germany and the United States. The measured values allowed for determination of the number of ultrafine particles per cubic centimeter, which are comparable to levels reported for Madrid and Brisbane. In what concerns outdoor/indoor levels, we observed higher levels (32 to 63%) outdoors, which is somewhat lower than levels observed in houses in Ontario.

Genotoxicity biomarkers in occupational exposure to formaldehyde: the case of histopathology laboratories

Formaldehyde, classified by the IARC as carcinogenic in humans and experimental animals, is a chemical agent that is widely used in histopathology laboratories. The exposure to this substance is epidemiologically linked to cancer and to nuclear changes detected by the cytokinesis-block micronucleus test (CBMN). This method is extensively used in molecular epidemiology, since it provides information on several biomarkers of genotoxicity, such as micronuclei (MN), which are biomarkers of chromosomes breakage or loss, nucleoplasmic bridges (NPB), common biomarkers of chromosome rearrangement, poor repair and/or telomere fusion, and nuclear buds (NBUD), biomarkers of elimination of amplified DNA. The aim of this study is to compare the frequency of genotoxicity biomarkers, provided by the CBMN assay in peripheral lymphocytes and the MN test in buccal cells, between individuals occupationally exposed and non-exposed to formaldehyde and other environmental factors, namely tobacco and alcohol consumption. The sample comprised two groups: 56 individuals occupationally exposed to formaldehyde (cases) and 85 unexposed individuals (controls), from whom both peripheral blood and exfoliated epithelial cells of the oral mucosa were collected in order to measure the genetic endpoints proposed in this study. The mean level of TWA8h was 0.16±0.11ppm (exposure to formaldehyde and the presence of genotoxicity biomarkers.

Effects of exposure to formaldehyde and tobacco smoking on genotoxicity biomarkers

Formaldehyde (FA) is a colour less gas widely used in the industry and hospitals as an aqueous solution, formalin. It is extremely reactive and induces various genotoxic effects in proliferating cultured mammalian cells. Tobacco smoke has been epidemiologically associated to a higher risk of development of cancer, especially in the oral cavity, larynx and lungs, as these are places of direct contact with many carcinogenic tobacco’s compounds. Approximately 90% of human cancers originate from epithelial cells. Therefore, it could be argued that oral epithelial cells represent a preferred target site for early genotoxic events induced by carcinogenic agents entering the body via inhalation and ingestion. The cytokinesis-blocked micronucleus assay (CBMN) in human lymphocytes is one of the most commonly used methods for measuring DNA damage, namely the detection of micronucleus, nucleoplasmic bridges, and nuclear buds.

Radiological imaging in digital systems: the effect of exposure parameters in diagnostic quality and patient dose

Esta tese pretende contribuir para o estudo e análise dos factores relacionados com as técnicas de aquisição de imagens radiológicas digitais, a qualidade diagnóstica e a gestão da dose de radiação em sistema de radiologia digital. A metodologia encontra-se organizada em duas componentes. A componente observacional, baseada num desenho do estudo de natureza retrospectiva e transversal. Os dados recolhidos a partir de sistemas CR e DR permitiram a avaliação dos parâmetros técnicos de exposição utilizados em radiologia digital, a avaliação da dose absorvida e o índice de exposição no detector. No contexto desta classificação metodológica (retrospectiva e transversal), também foi possível desenvolver estudos da qualidade diagnóstica em sistemas digitais: estudos de observadores a partir de imagens arquivadas no sistema PACS. A componente experimental da tese baseou-se na realização de experiências em fantomas para avaliar a relação entre dose e qualidade de imagem. As experiências efectuadas permitiram caracterizar as propriedades físicas dos sistemas de radiologia digital, através da manipulação das variáveis relacionadas com os parâmetros de exposição e a avaliação da influência destas na dose e na qualidade da imagem. Utilizando um fantoma contraste de detalhe, fantomas antropomórficos e um fantoma de osso animal, foi possível objectivar medidas de quantificação da qualidade diagnóstica e medidas de detectabilidade de objectos. Da investigação efectuada, foi possível salientar algumas conclusões. As medidas quantitativas referentes à performance dos detectores são a base do processo de optimização, permitindo a medição e a determinação dos parâmetros físicos dos sistemas de radiologia digital. Os parâmetros de exposição utilizados na prática clínica mostram que a prática não está em conformidade com o referencial Europeu. Verifica-se a necessidade de avaliar, melhorar e implementar um padrão de referência para o processo de optimização, através de novos referenciais de boa prática ajustados aos sistemas digitais. Os parâmetros de exposição influenciam a dose no paciente, mas a percepção da qualidade de imagem digital não parece afectada com a variação da exposição. Os estudos que se realizaram envolvendo tanto imagens de fantomas como imagens de pacientes mostram que a sobreexposição é um risco potencial em radiologia digital. A avaliação da qualidade diagnóstica das imagens mostrou que com a variação da exposição não se observou degradação substancial da qualidade das imagens quando a redução de dose é efectuada. Propõe-se o estudo e a implementação de novos níveis de referência de diagnóstico ajustados aos sistemas de radiologia digital. Como contributo da tese, é proposto um modelo (STDI) para a optimização de sistemas de radiologia digital.

Evaluation of exposure index (IgM) in orthopaedic radiography

The exposure index (lgM) obtained from a radiographic image may be a useful feedback indicator to the radiographer about the appropriate exposure level in routine clinical practice. This study aims to evaluate lgM in orthopaedic radiography performed in the standard clinical environment. We analysed the lgM of 267 exposures performed with an AGFA CR system. The mean value of lgM in our sample is 2.14. A significant difference (P=0.000<0.05) from 1.96 lgM reference is shown. Data show that 72% of exposures are above the 1.96 lgM and 42% are above the limit of 2.26. Median values of lgM are above 1.96 and below 2.26 for Speed class (SC) 200 (2.16) and SC400 (2.13). The interquartile range is lower in SC400 than in SC200. Data seem to indicate that lgM values are above the manufacturer’s reference of 1.96. Departmental exposure charts should be optimised to reduce the dose given to patients.