Hardwood Dust Research Articles

Genome-wide somatic mutation analysis of sinonasal adenocarcinoma with and without wood dust exposure

BackgroundSinonasal adenocarcinoma is a rare cancer, encompassing two different entities, the intestinal-type sinonasal adenocarcinoma (ITAC) and the non-intestinal-type sinonasal adenocarcinoma (non-ITAC). Occurrence of ITAC is strongly associated with exposure to hardwood dusts. In countries with predominant exposure to softwood dust the occurrence of sinonasal adenocarcinomas is lower and the relative amount of non-ITACs to ITACs is higher. The molecular mechanisms behind the tumorigenic effects of wood dust remain largely unknown.MethodsWe carried out whole-genome sequencing of formalin-fixed paraffin-embedded (FFPE) samples of sinonasal adenocarcinomas from ten wood dust-exposed and six non-exposed individuals, with partial tobacco exposure data. Sequences were analyzed for the presence of mutational signatures matching COSMIC database signatures. Driver mutations and CN variant regions were characterized.ResultsMutation burden was higher in samples of wood dust-exposed patients (p = 0.016). Reactive oxygen species (ROS) damage-related mutational signatures were almost exclusively identified in ITAC subtype samples (p = 0.00055). Tobacco smoke mutational signatures were observed in samples of patients with tobacco exposure or missing information, but not in samples from non-exposed patients. A tetraploidy copy number (CN) signature was enriched in ITAC subtype (p = 0.042). CN variation included recurrent gains in COSMIC Cancer Gene Census genes TERT, SDHA, RAC1, ETV1, PCM1, and MYC. Pathogenic variants were observed most frequently in TP53, NF1, CHD2, BRAF, APC, and LRP1B. Driver mutations and copy number gains did not segregate by subtype.ConclusionsOur analysis identified distinct mutational characteristics in ITAC and non-ITAC. Mutational signature analysis may eventually become useful for documentation of occupation-related cancer, while the exact mechanisms behind wood dust-driven carcinogenesis remain elusive. The presence of homologous recombination deficiency signatures implies a novel opportunity for treatment, but further studies are needed.

Health and Safety Executive research on wood dust exposure controls in British manufacturing.

To generate new intelligence on occupational exposure to wood dust in woodworking manufacturing activities in Britain, the Health and Safety Executive (HSE) performed 22 occupational hygiene site visits to assess exposure and exposure controls between 2014 and 2017. The work aimed to characterise good practice and therefore sites with a poor health and safety record, as identified from HSE inspection records, were not invited to participate. Sites selected covered furniture production, joinery, saw milling, and boat building and repair. Twenty-three follow-up telephone interviews were also carried out across 15 of the companies with supervisors and managers to explore how they tried to promote good practice among the workforce, and if there are any potential challenges encountered. The aim of the interviews was to gain a better understanding of how to enable organisations to improve the management of wood dust exposure. This study found that 6.0% of all wood dust exposure measurements (15 out of 252) were above 5 mg/m³, and 17.6% of exposures to hardwood dust or mixtures of hardwood and softwood dust (38 out of 216) were above 3 mg/m³ (the then current and future workplace exposure limits). Sanding, cleaning, and maintenance activities were of particular concern. Improvements to exposure controls are required, in particular, improvements to local exhaust ventilation controls for hand-held power tools and hand sanding. The management, selection, and use of respiratory protective equipment were poor. All the managers and supervisors recognised that exposure to wood dust can pose serious health risks, and that controls were crucial to protecting workers' health. The findings from the telephone interviews suggest that supervision and provision of information about the health effects of exposure to wood dust were common approaches that organisations used to raise awareness and promote good practice, in relation to managing wood dust exposure. Worker attitudes towards controls, such as perceptions that they hinder task completion and habitual ways of working, were identified as factors influencing the use of controls. Risk communication approaches that focus on increasing workers' awareness of their susceptibility to ill-health using credible sources, such as peers, can help enhance the uptake of messages on the use of controls. Financial constraints were identified as a challenge to improving the control of wood dust, particularly for small companies.

Effect of Hardwood Dust and Ammonia Gas on the Respiratory Integrity of Broiler Chickens.

Dust and ammonia gas (NH3) are two of the most abundant pollutants suspended in the air of poultry houses. Chronic inhalation of poultry dust and NH3 causes damage to the airways and reduces performance in broilers. Poultry dust is a mixture of organic and inorganic matter from feed, bedding material, manure, feathers, skin debris, and microorganisms. Thus, the composition and concentration of poultry dust vary among farms. This study proposes a model to assess the individual effect of a defined fraction of poultry dust derived from bedding material (wood dust) and its effects, alone or combined with NH3, on the performance and respiratory integrity of broilers. Ninety-six, 1-day-old broilers were randomly divided into groups of 24 and placed into four controlled environment chambers to continuously receive one of four treatments: 1) negative control; 2) exposure to airborne red oak wood dust at a concentration of 7.5 × 106 particles/m3 (particulate matter5.0); 3) exposure to 50 parts per million (ppm) of NH3; and 4) exposure to airborne red oak wood dust and 50 ppm of NH3. On day 43, all birds were weighed and euthanized. Performance data were recorded. Tissue samples were collected from six birds per treatment. Histologic evaluations of the nasal turbinates, trachea, and lungs were conducted. Histologic lesion scores (0 to 3) were assigned, and tracheal mucosal thickness was measured. No significant differences among treatments were found in body weight (P = 0.066), tracheal mucosal thickness (P = 0.593), or tracheal lesion score (P = 0.07). The average nasal turbinate lesion scores were higher in the wood and wood + ammonia treatments compared with the control (P = 0.015). The lung lesion scores were higher (P = 0.004) in all treatment groups compared with the control. In conclusion, chronic exposure to red oak wood dust, alone or in combination with NH3, induced important inflammatory damage to portions of the respiratory system of broilers; however, no significant effects on performance were observed.

Characteristics of thermally modified hardwood dust in determining workers’ occupational exposure

Thermal modification of wood changes its mechanical properties, generally reducing its strength, such that it is more easily chipped during processing than untreated hardwood. This study presents specific parameters used in the determination of mass concentration of thermally modified (TM) hardwood by gravimetric and photometric methods. An optical device, the Split 2, was used in the active mode, of which the holder of the inhalable dust IOM (Institute of Occupational Medicine) filter was the input part. Side-by-side determination of the respirable and inhalable mass concentration was made using the Higgins-Dewell respirable dust cyclone and an inhalable dust IOM sampler. Side-by-side determination of inhalable and total dust mass concentration was made using an IOM and open-faced (OF) filter holder to establish an IOM / OF sampling ratio. A correction factor of 1.16 was calculated for applying the photometric method as the ratio of mass concentration determined by gravimetric and photometric methods. Minimal concentrations of respirable and inhalable wood dust (geometric mean: cr = 0.058 mg/m3; cinh = 0.882 mg/m3) and a 12.76% share of respirable dust in the inhalable concentration cr / cinh, had a significant influence on the efficiency of the photometric method. The mass concentration obtained by IOM and OF samplers did not significantly differ (p = 0.36).

Flammability and explosion characteristics of hardwood dust

Wood dust consists of the fine particles of wood that are produced when wood is processed. It is considered explosive, especially if it produces a dust cloud. Initiating the combustion process inside the dust–air cloud spreads this process throughout the entire volume. In this article, experiment was carried out to study the influence of type of hardwood on combustion parameters. An experimental investigation was carried out to determine the evolution of the ignition sensitivity, fire behaviour and explosion characteristics of three types of hardwood dust. To determine dust behaviour under fire conditions, a cone calorimeter was used. Explosion characteristics were tested with the use of a 20 L spherical vessel and minimum ignition energy tested on MINOR II Apparatus, which is a modified Hartmann’s Tube. Studies have shown a large effect of particle size on explosion parameters, while for flammability parameters the effect is not so noticeable.

Occupational exposure to inhalable and respirable wood dust of pedunculate oak (Quercus robur L.) in a furniture factory

Given the well-known carcinogenicity of hardwood dust, occupational exposure to oak wood dust has been determined in a furniture factory on different wood processing machines during sanding, planing, and milling. Determination of the mass concentrations of respirable and inhalable oak wood dust from ambient air was performed using personal sampling pumps and two types of filter holders: the Higgins-Dewell respirable dust cyclone, manufactured by Casella (Bedford, UK), and the inhalable dust IOM sampler manufactured by SKC (Dorset, UK). Out of a total of 30 values of inhalable mass concentration, 7 (23%) exceeded the occupational exposure level (OEL). The highest exposure levels for inhalable and respirable wood dust from the belt sander were 1.569 to 3.710 mg/m3 and 0.243 to 1.342 mg/m3, respectively. Worker exposure may be below the level of increased risk of 2 mg/m3 if a machine such as a planer or router is connected to a suction system. The share of respirable particles in the inhalable fraction ranged between 12% and 31%, and for samples with an inhalable mass concentration exceeding 2 mg/m3, the share was lower than 16%, with a slightly decreasing tendency. Thus, the risk of lower respiratory tract diseases increases with higher exposure to inhalable particles, and the OEL is an indirect measure of protection against exposure to respirable particles.

Expect the unexpected – sinonasal papillary intestinal adenocarcinoma – A case report

Intestinal-type adenocarcinoma (ITAC) is the second most frequent sinonasal adenocarcinoma. High incidence of these tumors was seen among workers with occupational wood dust exposure, particularly of hardwood dusts. Furthermore, ITACs associated with dust exposure were diagnosed mostly in men (85–95%) and predominantly in the ethmoid sinus. This contrasts with sporadic ITACs that are more frequent in women and often arise in the maxillary antrum. ITAC had striking histomorphologic and immunophenotypic similarities with colorectal adenocarcinomas, but on the level of molecular pathologic mechanisms, these tumors have their own specific features different from gastrointestinal tumors. A 58-year-old female came with the chief complaints of difficulty in breathing and left-sided nasal obstruction for the past 1 month. On local examination, nasal septum was deviated to the right side on visualizing the left nasal cavity showed a polypoidal growth occupying the entire nasal cavity. Paranasal sinuses with contrast computed tomography (CT) showed a chronic granulomatous lesion in the left nasal cavity with surrounding inflammatory changes involving the ipsilateral sinuses. This patient was planned for functional endoscopic sinus surgery and specimen was sent for histopathological diagnosis. Contradictory to CT scan result, on gross and histopathology, the lesion was diagnosed to be intestinal type of sinonasal adenocarcinoma.

Sinonasal non-intestinal-type adenocarcinoma with isolate lagophthalmos and abducens nerve palsy: Case report

Abstract Sinonasal non-intestinal-type adenocarcinoma is a rare malignancy, with limited large-scale studies available in the medical literature. We present a case report of a 60-year-old male patient with sinonasal non-intestinal-type adenocarcinoma, isolate lagophthalmos and abducens nerve palsy, who had been exposed for 30 years to hard wood dust.

Proportionate mortality among workers exposed to hardwood dust in Italy.

The main aim of this study is to estimate the impact on workers' health caused by hardwood dust exposure in selected industrial sectors in Italy. Proportionate mortality ratios (PMR) by cancer site were calculated by linking the information on occupational exposure to carcinogens from the Italian national registry (SIREP, 1996-2018) to the national mortality archives (ISTAT, 2005-2018), assuming a Poisson distribution of the data. An elevated proportion of deaths from sino-nasal cancer was found in male exposed workers (PMR=4.25, CI 95%=1.37-13.23). Increased proportions of deaths were also found from stomach cancer in both genders (PMR=3.14, CI 95%=1.41-7.00 women; PMR=1.64, CI 95%=1.22-2.19 men). Although hardwood dust is a known human carcinogen, there are still many high-risk occupational exposure settings. Epidemiological surveillance and continuous monitoring of workers is highly recommended in order to ensure compliance with regulatory obligations and limit the burden of associated mortality causes.

Occurrence of Sinonasal Intestinal-Type Adenocarcinoma and Non-Intestinal-Type Adenocarcinoma in Two Countries with Different Patterns of Wood Dust Exposure.

Simple SummaryWood dust exposure is a reported pathogenetic factor for sinonasal intestinal-type adenocarcinoma, particularly in occupational exposure in wood-working industries. This study characterized wood dust exposure and compared the occurrence of sinonasal intestinal-type adenocarcinoma and non-intestinal-type adenocarcinoma between France with predominantly deciduous hardwood forests and Finland with mostly coniferous softwood forests. The findings indicated that sinonasal intestinal-type adenocarcinomas occur much more frequently in France than in Finland and are distinctly more common than non-intestinal adenocarcinomas, while in Finland the reverse is true. This is the first systematic comparison of the occurrence of the two tumor types in countries with distinctly different wood usage and wood dust exposure. It is also the first systematic study on differences in wood dust exposure between sinonasal intestinal-type adenocarcinoma and non-intestinal-type adenocarcinoma. The results provide important epidemiological information on pathogenetic differences between the two tumor types, highlighting the significance of the source of the wood dust.Sinonasal intestinal-type adenocarcinoma is strongly associated with hardwood dust exposure. Non-intestinal-type adenocarcinoma is a rarer and less well-known subtype considered not to be related with wood dust exposure. We determined the relative numbers of these two tumor types in 56 sinonasal adenocarcinoma patients in France and Finland, relating them with carefully assessed wood dust exposure histories. Diagnostic workup including immunohistochemistry for the intestinal markers CDX2 and CK20 indicated that the proportions of the two tumors differed significantly between France and Finland. In Finnish samples non-intestinal adenocarcinomas were more common than intestinal-type adenocarcinomas (12 non-intestinal vs. nine intestinal), while in the French samples the reverse was true (six non-intestinal vs. 29 intestinal). Such remarkably dissimilar occurrence of these tumors in France and Finland presumably reflects different pathogenetic circumstances in the two countries, and perhaps their different patterns of wood dust exposure. In France the main source of wood dust is from hardwoods. In Finland it is derived from softwoods. This is the first systematic comparison of the occurrence of intestinal-type adenocarcinoma and non-intestinal-type adenocarcinoma in two countries with different wood usage. It appears to be the first systematic study on differences in wood dust exposure between intestinal-type adenocarcinoma and non-intestinal-type adenocarcinoma.

Decreasing recurrence and increasing survival rates in patients of ethmoid or sphenoid intestinal-type adenocarcinomas: Systematic review and meta-analysis with 1126 cases.

Background:Ethmoid or sphenoid intestinal-type adenocarcinomas (ITACs) form a distinct subtype of sinonasal adenocarcinomas that occur less than 1 case/100,000/yr. They have obvious exposure relationship to hardwood or leather dusts, infrequent metastasis, but a relatively high local-recurrence rate. They locate at sinuses close to vital structures listed as high-risk areas in surgeries. Even in expert hands, a craniofacial resection is associated with non-negligible mortality and morbidity. Management of these tumors, first or recurrent, needs to weigh these consequences versus the survival, regional-recurrence, and distant-recurrence rates. Due to the rareness of ethmoid or sphenoid ITACs, accurate overall survival and local- or regional-recurrence rates across diverse treatments are unclear. The aim of this study is to report the overall statistics of this cancer and the relationship between enrollment year versus age, recurrence, and survival.Methods:Systemic review and meta-analysis with 1126 cases across various treatments in the literature.Results:Here, we show that patients of ethmoid or sphenoid ITACs had overall local-, regional-, and distant-recurrence rates of 32.2%, 2.2%, and 10.3%, respectively, with a 5-year overall survival rate of 66.2%. The results present a significant correlation between age, local-recurrent rate, or overall survival rate versus enrollment year.Conclusion:This suggests that recent patients of ethmoid or sphenoid ITACs may present at an older mean age, have a lower local-recurrence rate, and have a better 5-year survival rate than before. There was a shifting trend of treating ethmoid ITACs from external approach to endoscopic resection. Clinicians may want to weigh mortality and morbidity rates of external surgeries and these data to share or decide a solution.

APPLICATION OF PHOTOMETRY IN DETERMINING THE DUST MASS CONCENTRATION OF HARDWOODS

Given the carcinogenicity of hardwood dust, the aim of this study was to determine the effectiveness of the photometric method for different types of woodworking machines and its application in determining the mass concentration of inhalable dust for raw and dry hardwoods. In addition to the optical part of the device, the input part of the measuring device contains the Institute of Occupational Medicine (IOM) inhalable dust filter holder. This correlation of gravimetric and photometric methods in determining the dust mass concentration showed that photometry underestimates the mass concentration measured gravimetrically. The results of this study recommend the application of a correction factor 2 for a timber band saw and a correction factor 3 for circular saws in determining the mass concentration of hardwood dust by the photometric method. It was showed that photometry can be used if the correction factor of the optical device has been previously tested for specific wood processing place.

Wood dust – inhalable fraction. Documentation of proposed values of occupational exposure limits (OELs)

Wood is a raw material of the wood industry. Exposure to dust from deciduous trees (hardwood) or from a mixture with coniferous species (softwood) is correlated with nasopharyngeal adenocarcinomas. Occupational asthma is the result of actions of the biologically active compounds pre¬sent in some wood species (both hardwood and softwood). Hardwood and softwood dusts may impair clear airway, resulting in chronic lung disease. Taking into account the health effects and the socio-economic conditions of enterprises presented by the European Commission, we propose to lower the current TLV value from 3 mg/m3 to 2 mg/m3 for the inhalable fraction of wood dust, with the note that the TLV value applies to all types of wood dust. The proposed value corresponds to the binding value proposed by the European Commission (BOELV) for the inhalable fraction of hardwood dusts set at 2 mg/m3, taking into account the socio-economic conditions of enterprises. This value will apply in Poland and EU countries from January 18, 2023. The Commission of the European Union included research on exposure to hard and mixed wood dust to technological processes classified as carcino¬genic to humans (Directive 2017/2398/EC) and indicating that if there is a mixture of hardwood dust with other wood dust then MAC refers to the total wood dust present in the mixture. Due to the fact that wood dusts are carcinogenic, mutagenic and cause pneumoco¬niosis, the determination of STEL values is unjustified. Wood dust was labeled as a carcinogen with Annex 1 to the Regulation of Ministry of Health, and with letter “A” because of possible sensitization.

Reliability of the measurement method in determining the mass concentration of hardwood dust

The reliability of the measurement method in determining the mass concentration of wood dust relates to the sampling time for the detection of wood particles in the ambient air of woodworking places. The aim of this study was to calculate the mass limit of detection (LOD), limit of quantification (LOQ), and the minimal sampling time (tLOD and tLOQ) for determination and quantification of samples, based on the hardwood dust mass concentration at various woodworking places in the sawmills, floor production factories, and carpentries. Determination of the mass concentration of respirable, inhalable, and total hardwood dust from ambient air was performed using personal sampling pumps and three types of filter holders: respirable dust cyclone, Institute of Occupational Medicine IOM inhalable dust sampler, and total dust open-faced filter holder. The average limit of detection amounts to 0.052, 0.083, and 0.167 mg for respirable, inhalable, and total hardwood dust, respectively. The minimal detection sampling time for collecting all observed types of dust fractions ranged between 1.12 h and 1.72 h. The minimal quantification time for all collected hardwood dust samples ranged from 3.75 h to 5.51 h. Pearson’s correlation test showed that the reliability of the measurements was affected more by the dustiness of the workspace than the real sampling time.

Assessing chainsaw operators’ exposure to wood dust during timber harvesting

Exposure to wood dust during logging operations is generally associated with a variety of adverse health effects. The aim of the present study is to determine the exposure of forestry workers to wood dust during timber harvesting tasks in a cutover. The concentrations of inhalable hardwood dust produced from Fagus sylvatica and Quercus petraea as well as softwood dust from Pinus brutia stands were examined. In total, 24 samples were collected with the use of a Personal SKC Button Sampler. Dust collection was performed every working day. The study also took into account the duration of each work phase in which the chainsaw was used (running time) as well as the delays, during which the chainsaw was either at idle or not running at all (downtime). Measurements were carried out throughout the daily work of the logger, which lasted from June to September. Mean concentration of inhalable dust for an 8 h exposure was found to be approximately 4.84 mg m−3. Fifty per cent of the samples showed dust concentrations lower than 3.00 mg m−3, while in approximately 20.8% of the samples, dust levels were higher than 5 mg m−3. Results also revealed that the concentration of inhalable dust is in inverse proportion to the increase in breast height diameter, implying that larger trees generated lower dust amounts. Furthermore, timbering activities in Quercus petraea stand were found to result in higher dust concentrations.

Carcinogenic or mutagenic chemical substances and technological processes in the workplace in Poland in 2013-2017

The aim of this paper was to present data on occupational exposure to carcinogens and mutagens in Poland in 2013-2017, based on information sent to the "Central Register of Data on Exposure to Carcinogenic or Mutagenic Chemical Substances, Mixtures, Agents or Technological Processes," kept by the Nofer Institute of Occupational Medicine, Łódź, Poland. The legal bases, purpose and scope of data collection were also discussed. Data on occupational exposure to carcinogenic and mutagenic substances, mixtures and technological processes, submitted to the Central Register by Polish employers in 2013- 2017, were analyzed. The data were shown in various configurations and presented in the form of spatial distribution of the exposure to and occurrence of selected occupational carcinogens and mutagens. The number of chemical substances reported to the Central Register in the reference period had increased gradually since 2013. In 2017, 368 substances were reported, i.e., an increase of 21.1% compared to 2013. Also, the number of reporting enterprises increased (to over 4000 enterprises in 2017). The most common chemical agents in the reference years were formaldehyde, particular polycyclic aromatic hydrocarbons (PAH), benzene and chromium( VI) compounds. Among the technological processes, most of the plants reported works in exposure to hardwood dust (about 800 plants and over 10 000 to almost 15 000 exposed workers). It is necessary to legally define the term "exposure" and its quantification so that there would be no doubts for employers and supervision services about the number of people exposed in the workplace. Exposure spatial distribution maps are a transparent and easy-to-understand way of presenting data on exposure to occupational carcinogens and mutagens. Med Pr. 2020;71(2):187-203.

Wood dust – aspiration fraction Documentation of proposed values of occupational exposure limits (OELs)

Wood dust – aspiration fraction Documentation of proposed values of occupational exposure limits (OELs)

Prioritising action on occupational carcinogens in Europe: a socioeconomic and health impact assessment

Background:Work-related cancer is an important public health issue with a large financial impact on society. The key European legislative instrument is the Carcinogens and Mutagens Directive (2004/37/EC). In preparation for updating the Directive, the European Commission commissioned a study to provide a socioeconomic, health and environmental impact assessment.Methods:The evaluation was undertaken for 25 preselected hazardous substances or mixtures. Estimates were made of the number of cases of cancer attributable to workplace exposure, both currently and in the future, with and without any regulatory interventions, and these data were used to estimate the financial health costs and benefits.Results:It was estimated that if no action is taken there will be >700 000 attributable cancer deaths over the next 60 years for the substances assessed. However, there are only seven substances where the data suggest a clear benefit in terms of avoided cancer cases from introducing a binding limit at the levels considered. Overall, the costs of the proposed interventions were very high (up to €34 000 million) and the associated monetised health benefits were mostly less than the compliance costs.Conclusions:The strongest cases for the introduction of a limit value are for: respirable crystalline silica, hexavalent chromium, and hardwood dust.

Intestinal-Type Adenocarcinoma: Classification, Immunophenotype, Molecular Features and Differential Diagnosis

Intestinal-type adenocarcinoma is the second most frequent sinonasal adenocarcinoma. High incidence of these tumors is seen among workers with occupational wood dust exposure, particularly of hardwood dusts. Intestinal-type adenocarcinoma has striking histomorphologic and immunophenotypic similarities with colorectal adenocarcinomas, but on the level of molecular pathologic mechanisms these tumors have their own specific features different from gastrointestinal tumors. This article provides an update on current histopathologic classification of intestinal-type adenocarcinomas, their immunophenotypic properties, recent advances in molecular pathologic features and differential diagnostic considerations.

Analysis of dust exposure during chainsaw forest operations

In 1999, the European Union proclaimed hardwood dust carcinogenic based on the classification of the International Agency for Research on Cancer (IARC) issued in 1995. The operational exposure limit (OEL) for inhalable wood dust has been set to 5 mg m-3 by EU directives, though in different countries the OEL ranges from 1 to 5 mg m-3. The objective of this study was to determine the exposure to wood dust of forest workers in chainsaw cutting and processing and suggest possible countermeasures. The study took into consideration different silvicultural treatments (coppice clear cut, conifer thinning, conifer pruning, and sanitary cut) and chainsaw fuel (normal two-stroke gasoline mix and two alkylate fuels). All the forest operations were carried out in forests located in Central Italy, on the Apennine mountain range. During the tests, 100 samples were collected by means of personal SKC Button Sampler (one sample per worker per day). The results showed that exposure to wood dust varied widely with forest operation type, while no significant difference were found for different type of chainsaw fuel. The average wood dust concentration was about 1.5 mg m-3 for all operations except coppicing, which showed a mean level of about 2.1 mg m-3. About 93% of the samples showed a concentration lower than 3 mg m-3, and in only two samples (one in conifer pruning and one in clear cut in coppice), the concentration was slightly higher than 5 mg m-3.