Available data on naphthalene exposures: strengths and limitations

Metal-Organic Frameworks in Surface Enhanced Raman Spectroscopy-Based Analysis of Volatile Organic Compounds

Volatile Organic Compounds (VOC) are a major class of environmental pollutants hazardous to human health, but also highly relevant in other fields including early disease diagnostics and organoleptic perception of aliments. Therefore, accurate analysis of VOC is essential, and a need for new analytical methods is witnessed for rapid on-site detection without complex sample preparation. Surface-Enhanced Raman Spectroscopy (SERS) offers a rapidly developing versatile analytical platform for the portable detection of chemical species. Nonetheless, the need for efficient docking of target analytes at the metallic surface significantly narrows the applicability of SERS. This limitation can be circumvented by interfacing the sensor surface with Metal-Organic Frameworks (MOF). These materials featuring chemical and structural versatility can efficiently pre-concentrate low molecular weight species such as VOC through their ordered porous structure. This review presents recent trends in the development of MOF-based SERS substrates with a focus on elucidating respective design rules for maximizing analytical performance. An overview of the status of the detection of harmful VOC is discussed in the context of industrial and environmental monitoring. In addition, a survey of the analysis of VOC biomarkers for medical diagnosis and emerging applications in aroma and flavor profiling is included.

Assessment and Biodegradation of Polycyclic Aromatic Hydrocarbons in Soil and Water Around Petroleum Products Depot Suleja, Nigeria

Petroleum contamination constitutes a frequent incidence in various petroleum depots in Nigeria. In this study, the polycyclic aromatic hydrocarbons (PAHs) present in soil and water in communities around Petroleum Products Marketing Company (PPMC) Suleja, Nigeria, were evaluated and degraded using indigenous microorganisms. The samples sites were divided into 7 plots from where samples of water and soil were obtained: one within the PPMC depot, five from communities surrounding the depot, and the control 93,000 km from the depot. The microbial counts were determined using spread plate inoculation technique on minimal salt media. The microbial isolates were characterized and identified based on their cultural, biochemical, and molecular characteristics. The potential of the microbial isolates to utilize 0.05 mL of diesel, kerosene, engine oil, and crude oil was determined in a Bushnell Haas Broth, and the biodegradation was determined by total viable cell counts and spectrophotometry. The ability of the isolates to mineralize PAHs was also evaluated in a minimum salt media. The bacterial isolates were species of Streptococcus, Pseudomonas, Staphylococcus, Proteus, Escherichia, and Bacillus, while species of Penicillium, Aspergillus, Mucor, and Rhizopus were isolated among the fungi. Aspergillus niger strain ATCC 1015 and Bacillus thuringiensis strain M43 showed high capacity to utilize the 16 priority PAHs. The pahE1 gene was used by Bacillus thuringiensis, Pseudomonas aeruginosa and A. niger, while Penicillium notatum used pahE2 gene for the degradation of the PAH. The current study identified microbial isolates that can utilize priority PAHs, making them beneficial for oil spill bioremediation in tropical environments.

Emission characteristics of naphthalene from ship exhausts under global sulfur cap

The global sulfur limit regulation mandates the use of 0.5 % low sulfur fuel oil (LSFO) to reduce emissions of sulfur oxides (SOx), nitrogen oxides (NOx), and particulate matter (PM). However, the addition of naphthalene (Nap) to LSFO to stabilize its quality has led to an increase in polycyclic aromatic hydrocarbons (PAHs), with Nap being the main pollutant. This study investigates the effects of Nap in ship exhaust by analyzing the emission concentrations of volatile organic compounds (VOCs) and Nap in the exhaust of 16 ships, including 2 container ships, 6 bulk carriers, 1 tanker, 2 ferries, 3 fishing vessels, and 2 harbor crafts, based on USEPA method TO-15A. The results show that the percentage of Nap emissions in the exhaust gases of the 16 ship engines ranged from 77 % to 97 % of the total volatile organic compound (TVOC). The Nap concentration in the exhaust of fishing vessels, tanker, and harbor craft exceeded the occupational exposure limit of 50,000 μg/m3, with fishing vessels having the highest TVOC and Nap concentrations. The enhanced Nap emission in the air degrades air quality in port cities and poses an obvious potential public health risk. While the benefits of the global sulfur cap are being secured, additional efforts should be made to reduce the undetected side effects. Alternative stabilizers of LSFO should be considered, or Nap emission control should be boosted to mitigate the potential negative impact on harbor air quality.

Solvent-Free Determination of Selected Polycyclic Aromatic Hydrocarbons in Plant Material Used for Food Supplements Preparation: Optimization of a Solid Phase Microextraction Method

The exploitation of waste and by-products in various applications is becoming a cornerstone of the circular economy. A range of biomasses can be employed to produce food supplements. An example is a particular extract obtained from plant buds (rich in bioactive molecules), which can be easily retrieved from cities' pruning. In order to safely use this material, its possible contamination by organic pollutants needs to be estimated. A green and simple method to detect priority polycyclic aromatic hydrocarbons (PAHs) in bud samples by head space solid phase microextraction coupled to GC-MS was developed. This strategy, optimized through experimental design and response surface methodology, requires a minimal sample pre-treatment and negligible solvent consumption. The final method was found to be accurate and sensitive for PAHs with mass up to 228 Da. For these analytes, satisfactory figures of merit were achieved, with detection limits in the range 1-4 ng g-1, good inter-day precision (relative standard deviation in the range 4-11%), and satisfactory accuracy (88-105%), along with specificity guaranteed by the selected ion monitoring detection. The method was applied to bud samples coming from differently polluted areas, thus helping in estimating the safety of their use for the production of food supplements.

Remediation of phthalate acid esters from contaminated environment—Insights on the bioremedial approaches and future perspectives

Phthalates are well-known emerging pollutants that are toxic to the environment and human health. Phthalates are lipophilic chemicals used as plasticizers in many of the items for improving their material properties. These compounds are not chemically bound and are released to the surroundings directly. Phthalate acid esters (PAEs) are endocrine disruptors and can interfere with hormones, which can cause issues with development and reproduction, thus there is a huge concern over their existence in various ecological surroundings. The purpose of this review is to explore the occurrence, fate, and concentration of phthalates in various environmental matrices. This article also covers the phthalate degradation process, mechanism, and outcomes. Besides the conventional treatment technology, the paper also aims at the recent advancements in various physical, chemical, and biological approaches developed for phthalate degradation. In this paper, a special focus has been given on the diverse microbial entities and their bioremedial mechanisms executes the PAEs removal. Critically, the analyses method for determining intermediate products generated during phthalate biotransformation have been discussed. Concluisvely, the challenges, limitations, knowledge gaps and future opportunities of bioremediation and their significant role in ecology have also been highlighted.

Effects of coal chemical industry on atmospheric volatile organic compounds emission and ozone formation in a northwestern Chinese city

Coal is well known as the primary energy consumption in China, and the coal chemical industry (CCI) can serve as an important source of volatile organic compounds (VOCs) emissions. However, the characteristics of VOCs emitted from CCI along with their environmental consequences are still poorly understood. To pin down this, an intensive field campaign was carried out at a typical CCI city in northwestern China (Yulin) from February 26 to March 7, 2021. Results showed that VOC compositions in Yulin were distinct from those in the megacities of China as well as in the typical oilfields over the world. The concentration of naphthalene (1.6 ± 1.1 ppbv), an important byproduct of CCI, was significantly higher than that in other cities (<0.2 ppbv). Positive matrix factorization (PMF) model analysis revealed that the direct contribution of the CCI source for VOC emissions is 8.8 ± 1.8%. More importantly, these VOCs emitted from the CCI can account for 17.9 ± 6.8% of ozone (O₃) formation potential and 16.9 ± 7.4% of OH reactivity of VOCs, suggesting the significant impacts of the CCI on the air quality and atmospheric oxidizing capacity. During the observation, a rapid increase in O₃ concentration after a snowfall was encountered. The changing rate of O₃ concentration in the daytime was significantly higher than in its peripheral cities. The increased O₃ formation was partially attributed to the CCI, and this enhancement can be further magnified by snow cover due to the increment of surface albedo. These findings deepen the understanding of the characteristics and air quality impact of VOCs related to the CCI and provide valuable insights for the development of air quality control measures in the region influenced by intensive coal chemical production.

Using an insulating fiber as the sampling probe and ionization substrate for ambient ionization-mass spectrometric analysis of volatile, semi-volatile, and polar analytes

A sharp metal needle used as the ionization emitter in conventional atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) is usually required for analyte ionization through corona discharge (i.e., gas discharge). Nevertheless, we herein demonstrate that an insulating fiber (tip diameter: 10-60 µm; length: ~ 1 cm) made of glass or bamboo can function as an APCI-like ionization emitter. Although no direct electric contact is made on the fiber, the ionization of volatiles and semi-volatiles occurs when the fiber is placed close (~ 1 mm) to the inlet of the mass spectrometer. No analyte ion signals can be observed without placing the insulating fiber in front of the mass spectrometer. The generation of ion species mainly relies on the electric field provided by the mass spectrometer. Presumably, owing to the high electric field provided by the mass spectrometer, the dielectric breakdown voltages of gas molecules in the air and the fiber are overcome, leading to the ionization of analytes in gas phase. In addition, the insulating fiber can function as a holder for sample solutions. Electrospray ionization-like processes derived from polar analytes such as amino acids, peptides, and proteins can readily occur when the insulating fiber deposited with a sample droplet is placed close to the inlet of the mass spectrometer. The feasibility of using the current approach for the detection of nonpolar and polar analytes from complex fetal bovine serum samples without tedious sample pretreatment is demonstrated in this work. The main advantage of using the suggested fiber is that the fiber can be used as the sampling probe to pick up samples and placed in front of a mass spectrometer for direct MS analysis. The application of using a robust, insulating, and disposable probe to pick up samples from real samples such as onion, honey, and pork samples followed by direct MS analysis is also demonstrated.

Profiling of Primary Metabolites and Volatile Determinants in Mahlab Cherry (Prunus mahaleb L.) Seeds in the Context of Its Different Varieties and Roasting as Analyzed Using Chemometric Tools

Mahlab cherry (Prunus mahaleb L.) is a plant native to the Mediterranean basin and Eastern Europe, with several health benefits and culinary uses. We explored the compositional heterogeneity in the aroma profile and nutrients of three P. mahaleb seeds in the context of its cultivar type, i.e., white and red, and in response to roasting. A holistic untargeted metabolomics approach was employed for the first time using solid-phase microextraction (SPME-GC-MS) profiles of seed volatiles and primary metabolites coupled with chemometrics. Around 65 peaks belonging to sugars, fatty acids, esters and organic acids were identified by GC-MS. White mahlab from Egypt is rich in fatty acids, e.g., oleic and α-linolenic acids. Some acyl esters, e.g., glycerylmonostearate and n-butylcaprylate, characterized mahlab cultivars from various origins. A total of 135 volatiles were identified, with organic acids and aldehydes the most abundant. Aldehydes were the most discriminatory in seed origin and in accounting for its distinct aroma. Several roasting indices were identified, viz. 1-octanol, γ-caprolactone and isomintlactone. A direct relationship between furans and fatty acids was rationalized by cyclic transformation of the latter into furan derivatives. This study provides the first chemical evidence supporting the nutritional and flavor determinants of mahlab seeds, suggesting novel uses as a functional food.

Investigation by mass spectrometry and 32P post-labelling of DNA adducts formation from 1,2-naphthoquinone, an oxydated metabolite of naphthalene

Naphthalene is the simplest representative of polycyclic aromatic hydrocarbons (PAHs). It is detected as major pollutant in the different compartments of the environment. This compound is considered by the international agency for research on cancer (IARC), the specialized cancer agency of the World Health Organisation (WHO), as a possible carcinogenic (group 2B) since 2002, mainly based on studies on chronic inhalation in rodent by the national toxicology program of the U.S. department of health and human services. In humans, its main metabolites correspond to derivatives substituted in position and 1 and 2 as 1,2-naphthoquinone (1,2-NphQ). Based on previous studies, 1,2-NphQ is supposed to react with DNA to form mostly depurinating adducts, a possible initiating step of carcinogenicity. To confirm this potentiality, adducts were synthetized by the reaction of 1,2-NphQ with 2'-deoxyguanosine (2'-dG) in N,N-dimethylformamide (DMF), water and calf thymus DNA. 2'-dG adducts were analyzed by ³²P post-labelling, HPLC with ultra-violet detection and ultra-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). We found stable DNA adducts detected in DNA. We proposed a formation mechanism by a 1,4-Michael addition with 2'-dG. Adducts with 2'-deoxyxanthosine are formed after a spontaneous deamination of 2'-dG. These adducts are good candidates as biomarkers allowing evaluation of exposure to naphthalene and its derivatives in the development of pathologies such as cancer.

Non-linear relationships between seasonal exposure to polycyclic aromatic hydrocarbons and urinary 8-hydroxy-2'-deoxyguanosine levels among Chinese young students

Limited data are available on seasonal associations of polycyclic aromatic hydrocarbons (PAHs) exposure with oxidative DNA damage. We conducted a pilot study with 20 postgraduates, and measured urinary levels of mono-hydroxyl PAHs (OH-PAHs) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) for 7 consecutive days in the four seasons. We assessed the relationships of urinary OH-PAHs with urinary 8-OHdG in the whole year as well as cold- and warm-seasons. Summed OH-PAHs (∑OH-PAHs) were higher in cold season than in warm season. Each ln-unit (ln-transformed unit) increase in ∑OH-PAHs in the whole year corresponded to a 34%, 16% or 23% increase in urinary 8-OHdG levels at lag0, lag1 or lag2 day as well as a 26% increase in urinary 8-OHdG levels at lag0-2 days (cumulative effects). Each ln-unit increase in ∑OH-PAHs corresponded to a 36%, 26% or 46% increase in urinary 8-OHdG levels in cold season at lag0 day, lag1 day or lag2 day as well as a 36% increase in urinary 8-OHdG in warm season at lag0 day. Distributed non-linear cumulative lag models (DLNMs) indicated that each ln-unit increase in ∑OH-PAHs within the range of 5.7-8.1 nmol/mmol Cr had a stronger effect (coefficient β: 1.11-2.97 nmol/mmol Cr) on urinary 8-OHdG rather than non-cumulative DLNMs (coefficient β: 1.08-1.43 nmol/mmol Cr) as well as the non-linear dose-response relationships of ∑OH-PAHs with urinary 8-OHdG. PAHs exposure exhibited the lagged and cumulative effects on urinary 8-OHdG levels.

Modeling and evaluating spatial variation of polycyclic aromatic hydrocarbons in urban lake surface sediments in Shanghai

To explore the influence of rapid urbanization development on the accumulation of 16 priority PAHs in urban environment, thirty-three surface sediments from city lakes in different urbanized areas of Shanghai were collected to evaluate the occurrence characteristic and source apportionment of PAHs. The concentrations of Σ₁₆PAHs in lake surface sediments ranged from 55.7 to 4928 ng g^-1 with a mean value of 1131 ng g^-1 (standard deviation, 1228 ng g^-1), of which 4-, 5- and 6-ring PAHs were the dominant components. Spatial distribution of PAHs in lake surface sediments showed a significantly declining trend along with a decreasing urbanization gradient (one-way ANOVA, p < .05). Two hotspots of sediment PAHs were mainly distributed at highly urbanized areas with intensive population density and heavy traffic activities and at burgeoning industrial towns in the suburb. Source apportionment of total PAHs identified by a constrained positive matrix factorization model revealed that vehicle emission and combustion of coal, biomass and natural gas were the absolutely predominant sources, respectively accounting for 55.0% and 40.45% of total PAHs burden in lake sediments. Land use regression (LUR) models were successfully developed to evaluate spatial variation of PAHs contamination in urban sediments based on their significant correlations with residential land, commercial land, traffic variables, industrial sources, and population density. All PAH compounds showed strong associations with one or two source indicators (the traffic congestion index and the number of industrial sources), with the fitting R² varying from 0.529 to 0.984. Our findings suggest that energy consumption related to land use activities obviously promoted PAH accumulations in urban sediment environment during rapid development of urbanization and industrialization in Shanghai.

Volatile compounds emission and health risk assessment during composting of organic fraction of municipal solid waste

Degradation of mechanically sorted organic fraction (MSOF) of municipal solid waste in composting facilities is among the major contributors of volatile compounds (VCs) generation and emission, causes nuisance problems and health risks on site as well as in the vicinages. The aim of current study was to determine the seasonal (summer and winter) variation and human health risk assessment of VCs in the ambient air of different processing units in MSOF at composting plant in China. Average concentration of VCs was 58.50 and 138.03mg/m³ in summer and winter respectively. Oxygenated compounds were found to be the highest concentration (46.78-91.89mg/m³) with ethyl alcohol as the major specie (43.90-85.31mg/m³) in the two seasons respectively. Nevertheless, individual non-carcinogenic (Hazard relation i.e HR<1) and carcinogenic risk (CR<1.0E-04) of the quantified VCs were within acceptable limit except naphthalene at biofilter unit. In addition, cumulative non-carcinogenic risk exceeded from the threshold limit both in summers and winters in all units except at biofilter unit during winter. Furthermore cumulative carcinogenic risk also exceeded at same unit during the summer season. Therefore special attention should be made to minimize cumulative non-carcinogenic and carcinogenic risk as people are well exposed to mixture of compounds, not to individual.

"Upstream Analysis": An Integrated Promoter-Pathway Analysis Approach to Causal Interpretation of Microarray Data

A strategy is presented that allows a causal analysis of co-expressed genes, which may be subject to common regulatory influences. A state-of-the-art promoter analysis for potential transcription factor (TF) binding sites in combination with a knowledge-based analysis of the upstream pathway that control the activity of these TFs is shown to lead to hypothetical master regulators. This strategy was implemented as a workflow in a comprehensive bioinformatic software platform. We applied this workflow to gene sets that were identified by a novel triclustering algorithm in naphthalene-induced gene expression signatures of murine liver and lung tissue. As a result, tissue-specific master regulators were identified that are known to be linked with tumorigenic and apoptotic processes. To our knowledge, this is the first time that genes of expression triclusters were used to identify upstream regulators.

Urinary and breast milk biomarkers to assess exposure to naphthalene in pregnant women: an investigation of personal and indoor air sources

BACKGROUND

Naphthalene exposures for most non-occupationally exposed individuals occur primarily indoors at home. Residential indoor sources include pest control products (specifically moth balls), incomplete combustion such as cigarette smoke, woodstoves and cooking, some consumer and building products, and emissions from gasoline sources found in attached garages. The study aim was to assess naphthalene exposure in pregnant women from Canada, using air measurements and biomarkers of exposure.

METHODS

Pregnant women residing in Ottawa, Ontario completed personal and indoor air sampling, and questionnaires. During pregnancy, pooled urine voids were collected over two 24-hour periods on a weekday and a weekend day. At 2-3 months post-birth, they provided a spot urine sample and a breast milk sample following the 24-hour air monitoring. Urines were analyzed for 1-naphthol and 2-naphthol and breast milk for naphthalene. Simple linear regression models examined associations between known naphthalene sources, air and biomarker samples.

RESULTS

Study recruitment rate was 11.2% resulting in 80 eligible women being included. Weekday and weekend samples were highly correlated for both personal (r = 0.83, p < 0.0001) and indoor air naphthalene (r = 0.91, p < 0.0001). Urine specific gravity (SG)-adjusted 2-naphthol concentrations collected on weekdays and weekends (r = 0.78, p < 0.001), and between pregnancy and postpartum samples (r = 0.54, p < 0.001) were correlated.Indoor and personal air naphthalene concentrations were significantly higher post-birth than during pregnancy (p < 0.0001 for signed rank tests); concurrent urine samples were not significantly different. Naphthalene in breast milk was associated with urinary 1-naphthol: a 10% increase in 1-naphthol was associated with a 1.6% increase in breast milk naphthalene (95% CI: 0.2%-3.1%). No significant associations were observed between naphthalene sources reported in self-administered questionnaires and the air or biomarker concentrations.

CONCLUSIONS

Median urinary concentrations of naphthalene metabolites tended to be similar to (1-naphthol) or lower (2-naphthol) than those reported in a Canadian survey of women of reproductive age. Only urinary 1-naphthol and naphthalene in breast milk were associated. Potential reasons for the lack of other associations include a lack of sources, varying biotransformation rates and behavioural differences over time.

Sources, concentrations, and risks of naphthalene in indoor and outdoor air

Naphthalene is a ubiquitous pollutant, and very high concentrations are sometimes encountered indoors when this chemical is used as a pest repellent or deodorant. This study describes the distribution and sources of vapor-phase naphthalene concentrations in four communities in southeast Michigan, USA. Outdoors, naphthalene was measured in the communities and at a near-road site. Indoors, naphthalene levels were characterized in 288 suburban and urban homes. The median outdoor concentration was 0.15 μg/m(3), and a modest contribution from rush-hour traffic was noted. The median indoor long-term concentration was 0.89 μg/m(3), but concentrations were extremely skewed and 14% of homes exceeded 3 μg/m(3), the chronic reference concentration for non-cancer effects, 8% exceeded 10 μg/m(3), and levels reached 200 μg/m(3). The typical excess individual lifetime cancer risk was about 10(-4) and reached 10(-2) in some homes. Important sources include naphthalene's use as a pest repellent and deodorant, migration from attached garages and, to lesser extents, cigarette smoke and vehicle emissions. Excessive use as a repellent caused the highest concentrations. Naphthalene presents high risks in a subset of homes, and policies and actions to reduce exposures, for example, sales bans or restrictions, improved labeling, and consumer education, should be considered.

PRACTICAL IMPLICATIONS

Long-term average concentrations of naphthalene in most homes fell into the 0.2-1.7 μg/m(3) range reported as representative in earlier studies. The highly skewed distribution of concentrations results in a subset of homes with elevated concentrations and health risks that greatly exceed US EPA and World Health Organization (WHO) guidelines. The most important indoor source is the use of naphthalene as a pest repellant or deodorant; secondary sources include presence of an attached garage, cigarette smoking, and outdoor sources. House-to-house variation was large, reflecting differences among the residences and naphthalene use practices. Stronger policies and educational efforts are needed to eliminate or modify indoor usage practices of this chemical.

Urinary naphthol metabolites and chromosomal aberrations in 5-year-old children

BACKGROUND

Exposure to naphthalene, an International Agency for Research on Cancer (IARC)-classified possible carcinogen and polycyclic aromatic hydrocarbon (PAH), is widespread, though resulting health effects are poorly understood. Metabolites of naphthalene, 1- and 2-naphthol, are measurable in urine and are biomarkers of personal exposure. Chromosomal aberrations, including translocations, are established markers of cancer risk and a biodosimeter of clastogenic exposures. Although prenatal (maternal) PAH exposure predicts chromosomal aberrations in cord blood, few studies have examined chromosomal aberrations in school-age children and none has examined their association with metabolites of specific PAHs.

METHODS

Using Whole Chromosome Paint Fluorescent in situ Hybridization, we documented chromosomal aberrations including translocations, in 113 five-year-old urban minority children and examined their association with concurrent concentrations of PAH metabolites measured in urine.

RESULTS

We report that in lymphocytes, the occurrence and frequency of chromosomal aberrations including translocations are associated with levels of urinary 1- and 2-naphthol. When doubling the levels of urinary naphthols, gender-adjusted OR for chromosomal aberrations are 1.63 [95% confidence interval (CI), 1.21-2.19] and 1.44 (95% CI, 1.02-2.04) for 1- and 2-naphthol, respectively; and for translocations OR = 1.55 (95% CI, 1.11-2.17) and 1.92 (95% CI, 1.20-3.08) for 1- and 2-naphthol, respectively.

CONCLUSION

Our results show that markers of exposure to naphthalene in children are associated with translocations in a dose-related manner, and that naphthalene may be a clastogen.

IMPACT

Indoor exposure to elevated levels of naphthalene is prevalent in large regions of the world. This study is the first to present an association between a marker of naphthalene exposure and a precarcinogenic effect in humans.

Determination of cytotoxic and genotoxic effects of naphthalene, 1-naphthol and 2-naphthol on human lymphocyte culture

Naphthalene, a bicyclic aromatic hydrocarbon, has toxic effects on animals and humans. Although recent studies stressed on the genotoxic and cytotoxic effects of naphthalene and its metabolites on eukaryotic cells, there is a big controversy among the results of these studies. The aim of this study is to investigate the effects of naphthalene and its metabolites on the cytotoxicity and genotoxicity in the human lymphocytes in the culture. The genotoxic and cytotoxic effects of naphthalene and its metabolites, 1-naphthol and 2-naphthol, were studied using cytotoxicity test (lactate dehydrogenase and cell proliferation (WST-1) assays) and DNA fragmentation assay (terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay). Naphthalene and its metabolites had no significant cytotoxic effect on treated samples when compared with untreated ones. This result was also confirmed by WST-1 assay. In the TUNEL assay, DNA fragmentation was induced significantly by all concentrations of naphthalene and 2-naphthol and 50 and 100 µM concentrations of 1-naphthol ( p < 0.05 or 0.001). In the DNA fragmentation, the most effective dose of 2-naphthol (63%) was 100 µM, when compared with negative control group (13%). These results suggest that naphthalene and its metabolites, 1-naphthol and 2-naphthol, may cause DNA damage on human lymphocytes.

Naphthalene animal carcinogenicity and human relevancy: overview of industries with naphthalene-containing streams

Bioassays in mice and rats exposed via inhalation to naphthalene show incidences of lung and nasal cancer, respectively. To address the question of human relevancy, a literature search for cancer case reports in workers exposed to naphthalene was performed, along with an evaluation of major studies from industries with naphthalene-containing streams having the highest naphthalene exposures and/or most extensive epidemiology data. Although no epidemiologic studies of workers exposed solely to naphthalene were found, a population-based case-control study of oral and oropharynx cancer found no relation with naphthalene exposure. Limited case reports of laryngeal and colorectal cancer and naphthalene exposure exist, but these data are inadequate for evaluating human cancer risk. No case reports of nasal tumors were found, which is informative because case reports have historically identified several occupational carcinogens. Combined with anatomic and metabolic differences between rodent and human upper airways and data suggesting that cancer potency based on the rat bioassay is overestimated, relevancy of rat nasal tumors to humans is questionable. For lung cancer, existing human studies are insufficient to make firm conclusions about the presence or absence of a potential naphthalene-related risk, although no occupationally-related lung cancer risks were identified in the industries evaluated.

p53 codon 271 CGT to CAT mutant fraction does not increase in nasal respiratory and olfactory epithelia of rats exposed to inhaled naphthalene

A 2-year rat tumor bioassay testing whole body exposure to naphthalene (NA) vapor found a significant increase in nasal respiratory epithelial adenomas in male rats and in olfactory epithelial neuroblastomas in female rats. To obtain mechanistic insight into NA-induced nasal carcinogenesis, NA dose-response was characterized in nasal epithelium using a tumor-relevant endpoint. Specifically, levels of p53 codon 271 CGT to CAT mutation were measured in nasal respiratory and olfactory epithelium of NA-exposed male and female rats by allele-specific competitive blocker-PCR (ACB-PCR). Male and female, 8-9 week-old F344 rats (5 rats/group) were exposed to 0, 0.1, 1.0, 10, and 30ppm NA vapor for 13 weeks (6h/day, 5 days/week). The geometric mean p53 mutant fraction (MF) levels in nasal epithelium of control treatment groups ranged between 2.05 × 10(-5) and 3.05 × 10(-5). No significant dose-related changes in p53 mutant fraction (MF) were observed in the olfactory or respiratory epithelia of female rats. However, statistically significant treatment-related differences were observed in male respiratory and olfactory epithelium, with the p53 MF in the respiratory epithelium of male rats exposed to 30ppm NA significantly lower than that in controls. Further, a significant trend of decreasing p53 MF with increasing dose was observed in the male respiratory epithelium. Of the tissue types analyzed, respiratory epithelium is the most sensitive to the cytotoxic effects of NA, suggesting cytotoxicity may be responsible for the loss of p53 mutation. Because ACB-PCR has been used successfully to detect the effects of known mutagenic carcinogens, the absence of any significant increases in p53 MF associated with NA exposure adds to the weight of evidence that NA does not operate through a directly mutagenic mode of action.

Environmental and biological monitoring of exposures to PAHs and ETS in the general population

The objective of this study was to analyse environmental tobacco smoke (ETS) and PAH metabolites in urine samples of non-occupationally exposed non-smoker adult subjects and to establish relationships between airborne exposures and urinary concentrations in order to (a) assess the suitability of the studied metabolites as biomarkers of PAH and ETS, (b) study the use of 3-ethenypyridine as ETS tracer and (c) link ETS scenarios with exposures to carcinogenic PAH and VOC. Urine samples from 100 subjects were collected and concentrations of monophenolic metabolites of naphthalene, fluorene, phenanthrene, and pyrene and the nicotine metabolites cotinine and trans-3'-hydroxycotinine were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to assess PAH and ETS exposures. Airborne exposures were measured using personal exposure samplers and analysed using GC-MS. These included 1,3-butadiene (BUT), 3-ethenylpyridine (3-EP) (a tobacco-specific tracer derived from nicotine pyrolysis) and PAHs. ETS was reported by the subjects in 30-min time-activity questionnaires and specific comments were collected in an ETS questionnaire each time ETS exposure occurred. The values of 3-EP (>0.25 microg/m(3) for ETS) were used to confirm the ETS exposure status of the subject. Concentrations as geometric mean, GM, and standard deviation (GSD) of personal exposures were 0.16 (5.50)microg/m(3) for 3-EP, 0.22 (4.28)microg/m(3) for BUT and 0.09 (3.03)ng/m(3) for benzo(a)pyrene. Concentrations of urinary metabolites were 0.44 (1.70)ng/mL for 1-hydroxypyrene and 0.88 (5.28)ng/mL for cotinine. Concentrations of urinary metabolites of nicotine were lower than in most previous studies, suggesting very low exposures in the ETS-exposed group. Nonetheless, concentrations were higher in the ETS population for cotinine, trans-3'hydroxycotinine, 3-EP, BUT and most high molecular weight PAH, whilst 2-hydroxyphenanthrene, 3+4-hydroxyphenanthrene and 1-hydroxyphenanthrene were only higher in the high-ETS subpopulation. There were not many significant correlations between either personal exposures to PAH and their urinary metabolites, or of the latter with ETS markers. However, it was found that the urinary log cotinine concentration showed significant correlation with log concentrations of 3-EP (R=0.75), BUT (R=0.47), and high molecular weight PAHs (MW>200), especially chrysene (R=0.55) at the p=0.01 level. On the other hand, low correlation was observed between the PAH metabolite 2-naphthol and the parent PAH, gas-phase naphthalene. These results suggest that (1) ETS is a significant source of inhalation exposure to the carcinogen 1,3-butadiene and high molecular weight PAHs, many of which are carcinogenic, and (2) that for lower molecular weight PAHs such as naphthalene, exposure by routes other than inhalation predominate, since metabolite levels correlated poorly with personal exposure air sampling.

A critical review of naphthalene sources and exposures relevant to indoor and outdoor air

Both the recent classification of naphthalene as a possible human carcinogen and its ubiquitous presence motivate this critical review of naphthalene's sources and exposures. We evaluate the environmental literature on naphthalene published since 1990, drawing on nearly 150 studies that report emissions and concentrations in indoor, outdoor and personal air. While naphthalene is both a volatile organic compound and a polycyclic aromatic hydrocarbon, concentrations and exposures are poorly characterized relative to many other pollutants. Most airborne emissions result from combustion, and key sources include industry, open burning, tailpipe emissions, and cigarettes. The second largest source is off-gassing, specifically from naphthalene's use as a deodorizer, repellent and fumigant. In the U.S., naphthalene's use as a moth repellant has been reduced in favor of para-dichlorobenzene, but extensive use continues in mothballs, which appears responsible for some of the highest indoor exposures, along with off-label uses. Among the studies judged to be representative, average concentrations ranged from 0.18 to 1.7 microg m(-3) in non-smoker's homes, and from 0.02 to 0.31 microg m(-3) outdoors in urban areas. Personal exposures have been reported in only three European studies. Indoor sources are the major contributor to (non-occupational) exposure. While its central tendencies fall well below guideline levels relevant to acute health impacts, several studies have reported maximum concentrations exceeding 100 microg m(-3), far above guideline levels. Using current but draft estimates of cancer risks, naphthalene is a major environmental risk driver, with typical individual risk levels in the 10(-4) range, which is high and notable given that millions of individuals are exposed. Several factors influence indoor and outdoor concentrations, but the literature is inconsistent on their effects. Further investigation is needed to better characterize naphthalene's sources and exposures, especially for indoor and personal measurements.

Screening-level population risk assessment of nasal tumors in the US due to naphthalene exposure

Several naphthalene Unit Risk Factors (URFs) were proposed by the US Environmental Protection Agency in 2004 using data on the development of olfactory epithelial neuroblastomas and nasal respiratory epithelial adenomas in rats, but these URFs may be inappropriate and unnecessarily conservative for estimating human cancer risks. The purpose of the present exercise was to perform a screening-level population risk assessment of the US population to compare the observed number of naphthalene-induced nasal tumors in the US to the number that would be predicted if the URFs for naphthalene were as proposed. Nine scenarios were evaluated to represent the range of exposures individuals have typically experienced. Results indicate that the total predicted burden of naphthalene-induced nasal tumors per year in the US (65,905 rare nasal tumors, of which 29,121 are olfactory epithelial neuroblastomas) is much greater than the number of these tumors actually observed per year (910 total nasal tumors, of which 66 are olfactory neuroblastomas) over the period 1973-2006. This suggests that using rat nasal tumor data to derive a naphthalene URF for humans should be re-evaluated.

Exposure, epidemiology and human cancer incidence of naphthalene

This report provides a summary of deliberations conducted under the charge for members of Module B participating in the Naphthalene State-of-the-Science Symposium (NS(3)), Monterey, CA, October 9-12, 2006. The panel's charge was to derive consensus estimates of human exposure to naphthalene under various conditions, cancer incidence plausibly associated with these exposures, and identify quintessential research that could significantly reduce or eliminate material uncertainties to inform human cancer risk assessment. Relying in large part on a commissioned paper [Price, P.S., Jayjock, M.A., 2008. Available data on naphthalene exposures: strengths and limitations, in this issue], exposure levels were estimated for background (0.0001-0.003 microg/m(3)), ambient air (0.001-1.0 microg/m(3)), vehicles (0.003-3.0 microg/m(3)), residences (0.1-10 microg/m(3)), mothball use (on-label: 1-100 microg/m(3); off-label: 10-100 microg/m(3)), and occupational (low: 3-100 microg/m(3); high: 30-1,000 microg/m(3)). There have been few published reports of human cancer associated with naphthalene exposure. Several research projects are suggested that could reduce uncertainty in our understanding of human exposure. Using best scientific judgment, it is reasonably certain that the largest non-occupational exposures to naphthalene are indoor/residential exposures, particularly in households that use naphthalene-based products such as mothballs. However, even the highest of these exposures is likely to fall one or more orders of magnitude below moderate or high-level occupational exposure levels experienced by the few known cohorts exposed occupationally to naphthalene alone or as part of chemical mixtures such as jet fuel.

A review of whole animal bioassays of the carcinogenic potential of naphthalene

This report provides a summary of deliberations conducted under the charge for members of Module A participating in the Naphthalene State-of-the-Science Symposium (NS3), Monterey, CA, October 9-12, 2006. Whole animal bioassays have been performed by the National Toxicology Program in mice and rats to ascertain the carcinogenic potential of naphthalene by inhalation exposure. A statistically significant increased incidence of pulmonary alveolar/bronchiolar adenoma (a benign lesion), was observed among female mice; an observed increase among the males did not reach statistical significance. No nasal tumors were observed in either sex. A tumorigenic response was observed in both sexes of rats, in males an increased incidence of nasal respiratory epithelium adenoma (a benign rather than malignant lesion) and in females, olfactory epithelial neuroblastoma. Interpretations of these studies vary. On the one hand, evidence of extensive non-neoplastic response in both sexes of both species indicates cytotoxicity occurred at all doses, and strongly suggests that cytotoxicity played a significant role in the tumor responses observed in the target tissues. On the other hand, olfactory epithelial neuroblastoma has rarely been observed in NTP bioassays. This review seeks to develop a consensus understanding of the scientific evidence provided by these studies, taking into account that they have been used as the basis for quantitative human cancer risk assessment, and suggests scientific studies that, if performed, could resolve scientific uncertainties.