Wood Treatment Plant Research Articles

Determination of potentially toxic heavy metals in selected wood treatment sites in Uasin Gishu County and their associated health concerns

One of the monumental environmental and public health concerns of our time lies in the use of toxic preservatives in wood treatment plants. In this investigation, we report the results of potentially toxic heavy metals from wood treatment plants in Uasin Gishu County. A 20 g ground and sieved soil sample from each sampling site Cheplaskei (CK), Outspan (OS) and Sukunanga (SK) was weighed and treated with 0.5 M nitric acid for 2 h. The sample was then analyzed for potentially toxic metals using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The statistical treatment of the data was done using Principal component analysis (PCA) and Pearson’s correlation. The highest concentration of copper was observed at SK, which contributed approximately 37% of all the potentially toxic heavy metal content analyzed, whereas the concentration of lead was found to be about 33% of the total heavy metal content analyzed at the same sampling site. Furthermore, the most abundant metal in the sampled sites is manganese, which was found to be 390.0 ± 8.63, 279.0 ± 8.05and 44.5 ± 2.95 ppm in OS, CK, and SK, respectively. PCA showed that the heavy metals in the sample sites originated from two independent sources—natural and anthropogenic. Evidently from the concentration profile data, all the potentially toxic heavy metals had concentrations above the World Health Organization (WHO) acceptable limits, although, based on the contamination factors determined, the wood treatment sites are less polluted; however, there is need for regular monitoring to ensure adherence to proper public and environmental health practices.

Cancer risk associated with soil distribution of polycyclic aromatic hydrocarbons within three environmental justice neighborhoods in Houston, Texas.

Residents and advocacy groups began voicing concerns over the environmental quality located in the neighborhoods of Kashmere Gardens, Fifth Ward, and Denver Harbor in Houston, TX, following the confirmation of a cancer cluster in 2019 and another in 2021. These neighborhoods are in close proximity to a railyard and former wood treatment plant known to have utilized coal tar creosote and contain polycyclic aromatic hydrocarbons (PAHs). This research took core soil samples in September and October 2020 from 46 sites to assess for the presence and concentration of the U.S. Environmental Protection Agency's (USEPA) 7 Carcinogenic PAHs. Results showed the cumulative concentration of these PAHs in each sample was variable with a range of 13,767ng/g to 328ng/g and a mean of 2,517.2ng/g ± 3122. A regional soil screening evaluation revealed that 40 of the 46 soil samples were in excess of the USEPAs most conservative screening levels of 1.0 × 10-6 increased cancer risk, but none exceeding levels considered actionable for remediation. This study is a fundamental first step for quantifying the environmental pollutants in this minority-majority community. Findings revealed a low risk of cancer risk based on current PAH concentrations alone but cannot assess contributions from other contaminants or from past, possibly higher, levels of contamination. Further research is needed to identify the potential casual pathways of the observed cancer cluster and to explore possible remediation needs.

Histopathological Alterations in Gills of Neotropical Fish Cheirodon interruptus in an Environment Influenced by a Wood Treatment Plant

The gill epithelium has an important role in maintenance of ionic and osmotic balance of fish a getting as response to physiological and environmental factors. The aim of the present study was to evaluate the pathological alterations in the gills of the fish Cheirodon interruptus collected in the municipality of Triunfo – RS, in two consecutive years (2008 and 2009) from one point located inside the area of a wood treatment plant. The collected fish were fixed in formol 10% and preserved in 70% ethanol. The gills were removed and prepared using routine histological technique. The data demonstrated the occurrence of high frequency of moderate and severe changes in the two years of sampling in fishes. The Histopathological Alterations Index (HAI) demonstrated a small increase in 2009 as compared to 2008. The results suggest that individuals are suffering the action of stressors, but the gills may recover if there is an improvement of environmental conditions.

The role of lipopeptide biosurfactant on microbial remediation of aged polycyclic aromatic hydrocarbons (PAHs)-contaminated soil

Polycyclic aromatic hydrocarbons (PAHs) have been recognised as priority pollutants due to their carcinogenic, mutagenic and teratogenic properties. Bioremediation of PAHs is limited by low bioavailability of soil-bound PAHs due to their low aqueous solubility, high hydrophobicity and strong sorption to soil. The purpose of this study was to investigate the biodegradation enhancement potential of a heavy molecular mass lipopeptidal biosurfactant produced by Bacillus cereus SPL-4 on an aged wood treatment plant soil heavily contaminated with PAHs. In the laboratory scale batch treatments conducted (concentration of 6745.5mgkg−1, sum of 13PAHs) the high molecular weight PAHs removal rate was significantly enhanced in the biosurfactant supplemented microcosms than in the surfactant free controls. In the microcosms supplemented with 0.2 and 0.6% (w/w) lipopeptide, 51.2% of 4-ring and 55% of 5- and 6-ring PAHs; 64.1% of 4-ring and 79% of 5- and 6-ring PAHs were removed respectively, compared to 29% of 4-ring and 25.5% of 5- and 6-ring PAHs removal in the surfactant free control after 64daysof incubation. However, there was no statistically significant change in the degradation rates of low molecular weight PAHs in surfactant amended and surfactant free controls. Fitting the experimental data to two compartment model showed that the biosurfactant addition at 0.2 and 0.6% (w/w) increased the fast degradation fraction to 34.2 and 63% respectively, compared to 6% at the surfactant free controls. The degradation of 5 and 6 ring PAHs was significantly enhanced (p<0.05) in the higher surfactant dosage compared to the lower dosage. The results suggest that biosurfactant assisted degradation by microbial consortium may be a promising practical bioremediation strategy for aged PAH-contaminated soils.

Risk Perception And Communication F0llowing An Exposure Event At A Wood Treatment Plant: A before and after study.

Risk Perception And Communication F0llowing An Exposure Event At A Wood Treatment Plant: A before and after study.

Evaluation of area contaminated by wood treatment activities: Genetic markers in the environment and in the child population

Wood preservation activities and related compounds are a problem since these areas have major environmental contamination liabilities which compromise the health of the surrounding population and the integrity of ecological processes. The present study evaluated an area influenced by soil contamination arising from the activities of a deactivated wood treatment plant. The presence and effect of mutagenic compounds in environmental samples were used as markers of exposure together with the evaluation biomarkers of genetic damage in children. Organic extracts from samples of public source water and from fine atmospheric particulate matter (PM2.5) were evaluated for mutagenic potential using the Salmonella/microsome assay. Children living in the area surrounding the plant were analyzed for genetic damage assessed by the comet assay in lymphocytes and micronucleus test (MN) in lymphocytes and oral mucosa and compared to a group living in an area outside the preferential quadrant of atmospheric dispersion and in opposition to the drainage at the site. The mutagenic effect and PAHs concentrations found were similar to studies that evaluated intensely occupied urban areas and those under industrial influence. The MN frequencies in lymphocytes and binucleated cells in the oral mucosa were significantly higher in the risk group. No significant differences were observed in the other genetic damage biomarkers evaluated. The presence of pollutants with a mutagenic and carcinogenic effect on the PM2.5 and the increased in some biomarkers indicate that the population is potentially exposed to substances capable of causing adverse health effects and atmospheric airborne is a possible exposure route.

Biosurfactant from Paenibacillus dendritiformis and its application in assisting polycyclic aromatic hydrocarbon (PAH) and motor oil sludge removal from contaminated soil and sand media

A novel biosurfactant was produced by strain CN5, identified as Paenibacillus dendritiformis isolated from creosote contaminated wood treatment plant soil. The biosurfactant produced by the strain was identified as lipopeptidal after attenuated total reflectance Fourier transform infrared (ATR-FTIR), thin-layer chromatography (TLC), and liquid chromatography tandem mass spectrometry (LC–MS/MS) analysis. The MS/MS analysis of the biosurfactant showed that it has an amino acid sequence of Cys-Gly-Ala-Gly-Ile-Asn-Leu and a long chain fatty acid of molecular mass 522Da. The biosurfactant exhibited 74% and 82% emulsification index (E24) with hexane and cyclohexane respectively, and it showed high thermal, pH and saline stability over a wide range of temperature, pH and salinity. The ability of the biosurfactant to desorb PAH from spiked soils and motor oil from spiked sands was tested in batch experiments and it desorbed more than 96% of phenanthrene, 83% of pyrene from the contaminated soil in 5 days and 81% of heavy used motor oil sludge from the spiked sands in 24h. This suggests the potential application of the biosurfactant for the removal of PAHs and motor oil sludge from contaminated media and enhancing their bioremediation by increasing bioavailability and possible application of the biosurfactant for enhanced oil recovery.

The Elizabeth River Story: A Case Study in Evolutionary Toxicology

The Elizabeth River system is an estuary in southeastern Virginia, surrounded by the towns of Chesapeake, Norfolk, Portsmouth, and Virginia Beach. The river has played important roles in U.S. history and has been the location of various military and industrial activities. These activities have been the source of chemical contamination in this aquatic system. Important industries, until the 1990s, included wood treatment plants that used creosote, an oil-derived product that is rich in polycyclic aromatic hydrocarbons (PAH). These plants left a legacy of PAH pollution in the river, and in particular Atlantic Wood Industries is a designated Superfund site now undergoing remediation. Numerous studies examined the distribution of PAH in the river and impacts on resident fauna. This review focuses on how a small estuarine fish with a limited home range, Fundulus heteroclitus (Atlantic killifish or mummichog), has responded to this pollution. While in certain areas of the river this species has clearly been impacted, as evidenced by elevated rates of liver cancer, some subpopulations, notably the one associated with the Atlantic Wood Industries site, displayed a remarkable ability to resist the marked effects PAH have on the embryonic development of fish. This review provides evidence of how pollutants have acted as evolutionary agents, causing changes in ecosystems potentially lasting longer than the pollutants themselves. Mechanisms underlying this evolved resistance, as well as mechanisms underlying the effects of PAH on embryonic development, are also described. The review concludes with a description of ongoing and promising efforts to restore this historic American river.

Application of biosurfactant produced by Ochrobactrum intermedium CN3 for enhancing petroleum sludge bioremediation

The low water solubility of oil sludge and other petroleum hydrocarbon compounds is a major problem for their bioremediation. In this paper biosurfactant enhanced bioaviabability and subsequent degradation of oily sludge was investigated for that purpose, an efficient biosurfactant producing and oil sludge degrading bacterial strain CN3, identified as Ochrobactrum intermedium according to 16S rRNA gene sequencing, was isolated from wood treatment plant soil. The biosurfactant exhibited a high level of thermal stability, tolerance to extreme levels of salinity and a positive effect for increasing pH. The biosurfactant was identified as glycolipopeptidal after Fourier Transform Infrared (FT-IR) spectrometry, Thin Layer Chromatography (TLC), liquid chromatography/tandem mass spectrometry (LC–MS/MS) and biochemical compiosition analysis. The ability of the isolate to degrade petroleum sludge and the effect of its biosurfactant on biodegradation enhancement was tested in liquid culture experiments. The isolate degraded up to 40% of the hydrophobic long chain aliphatic and polycyclic aromatic hydrocarbons in liquid cultures with 4% (v/v) crude oil sludge while the biosurfactant amended microcosm showed up to 70% degradation of the most hydrophobic components of the petroleum sludge in 3 weeks. This suggests the potential application of the isolate and its biosurfactant in bioremediation of contaminated environment and microbial enhanced oil recovery.

Performance evaluation of anaerobic baffled reactor (ABR) treating pulp and paper wastewater in start-up period

This essay outlines the use of an anaerobic baffled reactor (ABR) treating pulp and paper wastewater during its start-up period. For this purpose, a pilot with four chambers and overall volume of 45 liters was fed continuously through the equalization tank of Mazandaran wood and paper wastewater treatment plant, in the north of Iran. The influent was classified as low strength slowly biodegradable wastewater. The average soluble chemical oxygen demand (SCOD) and biochemical oxygen demand (BOD) of the influent were about 1,130 and 320 mg/L, respectively. Results show that the start-up was accomplished in 90 days in which the ABR reached its maximum SCOD removal of 60%. This was achieved at the controlled mesophilic temperature (37 °C) and optimum hydraulic retention time (HRT) of 24 hours. In spite of the influent characteristics, the performance of ABR has not been inhibited and mostly influenced by HRT. The gradual hydrolysis and acidogenesis were observed within the ABR. The majority of chemical oxygen demand (COD) removal takes place in the first chamber. In addition, the concentrations of readily biodegradable organics (BOD to COD ratio) have been increased and doubled through the reactor. Moreover, the total values of pH, volatile fatty acids and alkalinity remained constant. Consequently, this system can be approved for application as a pretreatment unit for paper mill industrial wastewater treatment plants.

Petroleum Hydrocarbon Spills in the Environment and Abundance of Microbial Community Capable of Biosurfactant Production

Petroleum industries generate wastes, some of which may be considered hazardous because of the presence of toxic organics and heavy metals. The wastes can bioaccumulate in food chains where they disrupt biochemical or physiological activities of many organisms, thus causing carcinogenesis of some organs, mutagenesis in the genetic material, impairment in reproductive capacity. Bioremediation constitutes the primary mechanism for the elimination of hydrocarbons from contaminated sites by natural existing populations of microorganisms. In this work, microbial community composition and metabolic potential have been explored in petroleum-hydrocarbon contaminated wood treatment plant soil. A collection of strains, adapted to grow on minimal medium supplemented with coal tar creosote, was obtained and the diversity of the bacterial collection was analysed by 16S rRNA gene-based 454 pyrosequencing. Sequencing of the bands revealed a high proportion of Proteobacteria represented by the Alpha, Beta and Gamma subclasses, suggesting that Proteobacteria and especially Gamma subclass is a dominant group in coal tar creosote contaminated soils. The biotechnological potential of the operational taxonomic units (OUTs) revealed a significant degradation of creosote PAHs and production of biosurfactant with important emulsification activities during the bioremediation process.

Heterocyclic aromatic hydrocarbons show estrogenic activity upon metabolization in a recombinant transactivation assay.

Heterocyclic aromatic hydrocarbons (hetero-PAHs) are increasingly studied at contaminated sites; especially at former industrial facilities where coal tar-oil was handled, e.g., wood treatment plants, high concentrations of hetero-PAHs are frequently detected in groundwater plumes. In previous studies, fractions of groundwater with high estrogenic activity contained hetero-PAHs and their hydroxylated metabolites. To evaluate this preliminary evidence, selected hetero-PAHs were screened for their estrogenic activity in lyticase yeast estrogen screen (LYES) and ER CALUX. All tested substances were inactive in the LYES. Hetero-PAHs such as acridine, xanthene, indole, 2-methylbenzofuran, 2,3-dimethylbenzofuran, dibenzofuran, dibenzothiophene, quinoline, and 6-methylquinoline were positive in the ER CALUX, with estradiol equivalence factors (EEFs) from 2.85 × 10(-7) to 3.18 × 10(-5). The EEF values of these substances were comparable to those of other xenoestrogens (e.g., alkylphenols or bisphenol A) that are sometimes found in surface water. Chemical analyses revealed that T47Dluc cells could metabolize most of the substances. Among the metabolites (tentatively) identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) were hydroxides and their keto tautomers, sulfates, sulfoxides, and N-oxides. Because of their high concentrations measured in groundwater, we conclude that hetero-PAHs and metabolites may be a potential risk and should be the subject of further research.

Attic dust assessment near a wood treatment plant: Past air pollution and potential exposure

The wood treatment process uses substances that generate hazardous compounds that may contaminate environmental compartments. In the present study, an area under influence of a deactivated wood treatment plant was investigated to evaluate past air pollution and to try to understand local air dispersion. Attic dust samples were collected from eight residences around the plant and from two residences outside this area, as reference samples. The presence of copper, chromium, arsenic, pentachlorophenol, sixteen priority polycyclic aromatic hydrocarbons and mutagenic activity using Salmonella/microsome assay was evaluated. The residences close to the entrance to the plant were the most affected, according to potentially toxic elements analysis. The PCP concentration was 0.49mg/kg and the total PAHs content ranged from 0.40 to 13.31μg/g with greater dispersion than potentially toxic elements. The highest mutagenesis values were 15,905 and 10,399 revertants/g of dust in the absence and presence of S9 mix (mammalian metabolic activation), respectively. Samples in which the total PAHs concentration was less than 2μg/g no mutagenic effects were observed, including the residences in the reference area. The contribution of PAHs to mutagenesis was 10 percent, indicating that other compounds may contribute to the mutagenic effect. These results suggest that the population was or is potentially exposed to substances with strong effects on health.

Bacillus subtilis as a bioindicator for estimating pentachlorophenol toxicity and concentration

Pentachlorophenol (PCP) and its sodium salt (Na-PCP) are extremely toxic chemicals responsible for important soil and groundwater pollution, mainly caused by wastes from wood-treatment plants, because chlorinated phenols are widely used as wood preservatives. The methods most commonly used for routine analysis of pesticides such as PCP and Na-PCP are high-performance liquid chromatography (HPLC) and gas chromatography-mass spectroscopy (GC-MS). A variety of rapid biological screening tests using marine organisms, bioluminescent bacteria, and enzymes have also been reported. In this study, rapid biological screening analysis using Bacillus subtilis was developed, to assess the biodegradation of PCP and its by-products in liquid samples. An empirical model is proposed for spectrophotometric analysis of Na-PCP concentration after growth of Bacillus subtilis.

Occurrence and sources of polychlorinated dibenzo- p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls in surficial sediments of Lakes Superior and Huron

Concentrations and congener profile patterns of 2378-substituted PCDD/Fs and DLPCBs in offshore, nearshore and tributary sediments of Lakes Superior and Huron are reported, and spatial trends and source contributions assessed. PCDD/F concentrations ranged from 5 to 18 000 pg/g dw (Lake Superior) and 3 to 6100 pg/g dw (Lake Huron); DLPCBs ranged from 9 to 11 000 pg/g dw (Lake Superior) and 9 to 27 000 pg/g dw (Lake Huron). Our analysis indicated atmospheric deposition is a primary source to depositional areas of both lakes; however, greater PCDD/F and DLPCB concentrations were observed at several nearshore and tributary sites, and were attributed to corresponding land use in the watershed. Statistical analysis and pattern comparison suggested that industrial inputs mainly associated with wood treatment plants, pulp and paper mills, mining operations, and chlorine-based chemical manufacturing also contributed to contamination by PCDD/Fs and DLPCBs in certain nearshore and offshore areas of Lakes Superior and Huron.

Arsenic Exposure May Be a Risk Factor for Alzheimer's Disease

Arsenic Exposure May Be a Risk Factor for Alzheimer's Disease

Residential and biological exposure assessment of chemicals from a wood treatment plant

This paper evaluates the results of contamination of residents and residential homes located in close proximity to a Wood Treatment Plant. The plant has produced treated wood products continuously since 1904. The principle chemicals used to treat the wood, which is primarily used for railroad ties (oblong objects laid perpendicular to the rails to act as a base for the tracks), are creosote and pentachlorophenol. For a number of years, the plant burned treated waste wood products containing creosote and pentachlorophenol. First the plant pressure impregnates the wood with creosote and pentachlorophenol, and then the wood is stacked on open ground to allow it to air dry. Chemicals from recently treated wood ties are allowed to evaporate into the air or drip onto the ground surrounding the stacked wood. Small drainage ditches carry the liquid wastes into larger water channels where eventually the waste streams are discharged into a river adjacent to the plant. The river serves as a source of drinking water for the nearby community. Prevailing wind patterns favor a drift of air emissions from the plant's boiler stack over the nearby community and its residents. Over the past few years, the town's residents have become increasingly concerned about their health status and have voiced concerns regarding multiple health problems (including cancer), possibly associated with plant discharges. The intention of this study is to examine a representative sample of the potentially affected residents and to evaluate their residential environment for the presence of dioxin and/or its congeners. Data obtained from EPA's Toxic Release Information (TRI) database revealed the plant routinely discharged creosote, pentachlorophenol, dioxin and dioxin-like compounds into the ambient air via fugitive air emissions and surface waste waters. Sampling of household dust and water sediment within and outside of residences within a 2-mile radius of the plant revealed the presence of significantly elevated levels of dioxins, principally octachlorodibenzo-p-dioxin (OCDD) and 1,2,3,4,6,7,8-hepta-CDD. Biomonitoring of 29 subjects identified the presence of significantly elevated chlorinated dioxins and furan levels (OCDD=1049 ppt for exposed and 374 ppt for controls and 1,2,3,4,6,7,8-hepta CDD=132 ppt for exposed and 45.1 ppt for controls). These levels are consistent with exposures to pentachlorophenol in this group of subjects. And they confirm the presence of unsafe levels of chlorinated dioxins in these persons.

Biodegradation of phenol, o-cresol, m-cresol and p-cresol by indigenous soil fungi in soil contaminated with creosote

Seven non-basidiomycetic fungi, Aspergillus, Candida, Cladosporium, Fusarium, Monicillium, Trichoderma and Penicillium, and two basidiomycetic fungi, Pleurotus and Phanerochaete were isolated from a creosote-contaminated soil by using mineral salts medium and soil extract broth containing antibiotics. Soil contaminated with phenol, o-cresol, m-cresol and p-cresol was collected from the yard of a wood treatment plant in South Africa and inoculated with the strains of Aspergillus, Cladosporium, Fusarium, Monicillium, Penicillium and Phanerochaete, selected from the isolate. The soil in some of the treatment reactors was amended with nutrient supplements to give a C:N:P ratio of 25:5:1. A total of 18 duplicate treatments were established and incubated in the dark at 25°C for 70days. The soil in all the reactors was tilled weekly and moisture was maintained at 70% field capacity. Soil samples were collected every 2weeks for analysis of residual concentrations of the phenols tested, pH measurement and moisture content determination. The nutrient-supplemented treatments were more effective in degrading the phenols (between 84 and 100%) than those that were not supplemented. Barley, which was used as bulking agent enhanced the growth of the fungi and subsequently the degradation of the phenols. Inoculation with a mixture of the six fungal isolates promoted more phenol degradation than with single isolates.

631 National assessment of long-term use of paraquat for its food and environmental-safety in Korea

Polycyclic aromatic hydrocarbons (PAHs) have been recognised as priority pollutants due to their carcinogenic, mutagenic and teratogenic properties. Bioremediation of PAHs is limited by low bioavailability of soil-bound PAHs due to their low aqueous solubility, high hydrophobicity and strong sorption to soil. The purpose of this study was to investigate the biodegradation enhancement potential of a heavy molecular mass lipopeptidal biosurfactant produced by Bacillus cereus SPL-4 on an aged wood treatment plant soil heavily contaminated with PAHs. In the laboratory scale batch treatments conducted (concentration of 6745.5 mg kg−1, sum of 13 PAHs) the high molecular weight PAHs removal rate was significantly enhanced in the biosurfactant supplemented microcosms than in the surfactant free controls. In the microcosms supplemented with 0.2 and 0.6% (w/w) lipopeptide, 51.2% of 4-ring and 55% of 5- and 6-ring PAHs; 64.1% of 4-ring and 79% of 5- and 6-ring PAHs were removed respectively, compared to 29% of 4-ring and 25.5% of 5- and 6-ring PAHs removal in the surfactant free control after 64 days of incubation. However, there was no statistically significant change in the degradation rates of low molecular weight PAHs in surfactant amended and surfactant free controls. Fitting the experimental data to two compartment model showed that the biosurfactant addition at 0.2 and 0.6% (w/w) increased the fast degradation fraction to 34.2 and 63% respectively, compared to 6% at the surfactant free controls. The degradation of 5 and 6 ring PAHs was significantly enhanced (p < 0.05) in the higher surfactant dosage compared to the lower dosage. The results suggest that biosurfactant assisted degradation by microbial consortium may be a promising practical bioremediation strategy for aged PAH-contaminated soils.

Sources of interference in field studies of diesel exhaust emissions.

This article describes interferences encountered in a variety of occupational settings during industrial hygiene surveys of diesel particulate material (DPM) using the NIOSH 5040 Method. The method yields time-weighted-average measurements of elemental carbon (EC), organic carbon (OC), and total carbon (TC = EC + OC). NIOSH recommends EC as proxy for DPM, but other agencies (e.g., MSHA) regulate exposure as TC. Surveys were conducted in an engine factory and a wood treatment plant where diesel equipment was used, and in a foundry where its use was being considered. Full shift samples were collected using open-faced cassettes and cyclones fitted with 37-mm quartz fiber filters analyzed by the NIOSH 5040 Method. Non-DPM-related interferences were noted for both the OC and EC. In the engine factory and wood treatment facility, OC measurements were very high (range of 10.0-1600 microg/m(3)), while EC levels were mostly below the LOD. These findings almost certainly reflect interferences by cutting oil mists and airborne creosote respectively. In the foundry, EC levels were high and comprised mainly of larger (>4 microm) particles (open face samples: arithmetic mean = 136 microg/m(3), geometric mean = 74.0 microg/m(3); cyclone samples: arithmetic mean = 30.2 microg/m(3), geometric mean = 14.7 microg/m(3)). These findings suggest that OC interferences should be suspected if the EC:TC ratio is <0.35 and, if DPM surveys are performed with open-faced samplers, at least a small number of size-selective samplers should be employed to assure that results do not reflect EC interference by larger (i.e., >1-4 microm) particles. They also support the ACGIH decision to modify its proposed DPM TLV to specifically consider elemental carbon, rather than total carbon.