Genotoxicity and apoptosis in Drosophila melanogaster exposed to benzene, toluene and xylene: attenuation by quercetin and curcumin

Monocyclic aromatic hydrocarbons (MAHs) such as benzene, toluene and xylene are being extensively used for various industrial and household purposes. Exposure to these hydrocarbons, occupationally or non-occupationally, is harmful to organisms including human. Several studies tested for toxicity of benzene, toluene and xylene, and interestingly, only a few studies looked into the attenuation. We used Drosophila model to test the genotoxic and apoptotic potential of these compounds and subsequently evaluated the efficiency of two phytochemicals, namely, quercetin and curcumin in attenuating test chemical induced toxicity. We exposed third instar larvae of wild type Drosophila melanogaster (Oregon R⁺) to 1.0-100.0 mM benzene, toluene or xylene, individually, for 12, 24 and 48 h and examined their apoptotic and genotoxic potential. We observed significantly (P < 0.001) increased apoptotic markers and genotoxicity in a concentration- and time-dependent manner in organisms exposed to benzene, toluene or xylene. We also observed significantly (P < 0.001) increased cytochrome P450 activity in larvae exposed to test chemicals and this was significantly reduced in the presence of 3′,4′-dimethoxyflavone, a known Aryl hydrocarbon receptor (AhR) blocker. Interestingly, we observed a significant reduction in cytochrome P450 activity, GST levels, oxidative stress parameters, genotoxic and apoptotic endpoints when organisms were exposed simultaneously to test chemical along with quercetin or curcumin. The study further suggests the suitability of D. melanogaster as an alternate animal model for toxicological studies involving benzene, toluene and xylene and its potential in studying the protective role(s) of phytochemicals.     

Use of the γH2AX assay for assessing the genotoxicity of polycyclic aromatic hydrocarbons in human cell lines

The development of in vitro genotoxic assays as an alternative method to animal experimentation is of growing interest in the context of the implementation of new regulations on chemicals. However, extrapolation of toxicity data from in vitro systems to in vivo models is hampered by the fact that in vitro systems vary in their capability to metabolize chemicals, and that biotransformation can greatly influence the experimental results. Therefore, much attention has to be paid to the cellular models used and experimental conditions. Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic ubiquitous pollutants. Human exposure to PAHs is mainly from food origin. In this study, a detailed analysis of the biotransformation capabilities of three human cell lines commonly used for in vitro testing (HepG2, ACHN and Caco-2) was undertaken using 3 model PAHs (benzo(a)pyrene [B(a)P], fluoranthene [FLA] and 3-methylcholanthrene [3-MC]). Concomitantly the genotoxicity of these PAHs was investigated in different cell lines, using a new genotoxic assay (H2AX) in 96-well plates. The metabolic rates of B(a)P, FLA and 3-MC were similar in HepG2 and Caco-2 cell lines, respectively, though with the production of different metabolites. The ACHN cell line was shown to express very limited metabolic capabilities. We demonstrated that the PAHs having a high metabolic rate (B(a)P and 3-MC) were genotoxic from 10⁻⁷ molar in both HepG2 and Caco-2 cells. The present study shows that H2AX measurement in human cell lines competent for the metabolism, is an efficient and sensitive genotoxic assay requiring less cells and time than other currently available tests.     

Evaluation of genotoxicity potential of household effluents from onsite wastewater treatment systems using umu test

ABSTRACT

Household effluents are predominantly treated by wastewater treatment plants (WWTPs). Other treatment methods, which were examined in this study, are also used in the countryside. These treatment modes include (1) onsite toilet wastewater treatment system (OTWTS), (2) onsite wastewater treatment system (OWTS), (3) community wastewater treatment system (CWTS), and (4) onsite vault toilet (OVT). Household effluents consist of excrements and urine released from toilets as well as wastewater released from kitchens and bathrooms. In the present study, household effluents that were discharged from the residential areas having undergone similar treatment methodologies were compared using the umu test, an in vitro bioassay to assess genotoxicity potential. The different treatment methodologies were categorized based upon whether the two kinds of wastewater were mixed or not mixed and treated or not treated. Treated wastewater containing excrements and urine from the OTWTS exhibited the strongest genotoxicity potential compared to other effluents, whereas most of the kitchen and bathroom wastewater from OVT did not display genotoxicity. Data indicated that the genotoxicants in the effluents originated primarily from excrements and urine, and may increase an adverse environmental risk.     

Polycyclic aromatic hydrocarbon levels in three pelagic fish species from Atlantic Ocean: inter-specific and inter-season comparisons and assessment of potential public health risks

The concentrations of 18 polycyclic aromatic hydrocarbons (PAHs) were determined in three commercially valuable fish species (sardine, Sardina pilchardus; chub mackerel, Scomber japonicus; and horse mackerel, Trachurus trachurus) from the Atlantic Ocean. Specimens were collected seasonally during 2007–2009. Only low molecular weight PAHs were detected, namely, naphthalene, acenaphthene, fluorene and phenanthrene. Chub mackerel (1.80–19.90 μg/kg ww) revealed to be significantly more contaminated than horse mackerel (2.73–10.0 μg/kg ww) and sardine (2.29–14.18 μg/kg ww). Inter-specific and inter-season comparisons of PAHs bioaccumulation were statistically assessed. The more relevant statistical correlations were observed between PAH amounts and total fat content (significant positive relationships, p ? 0.05), and season (sardine displayed higher amounts in autumn–winter while the mackerel species showed globally the inverse behavior). The health risks by consumption of these species were assessed and shown to present no threat to public health concerning PAH intakes.     

Formation of polycyclic aromatic hydrocarbons from tobacco: the link between low temperature residual solid (char) and PAH formation.

The formation of condensed ring polycyclic aromatic hydrocarbons (PAHs) from the pyrolysis of ground tobacco in helium over the temperature range of 350-600 degrees C was investigated. PAH yields in the ng/g range were detected and the maximum yields of all PAHs studied including benzo[a]pyrene (B[a]P) and benzo[a]anthracene (B[a]A) occurred between 500 and 550 degrees C. The pathway to PAH formation in the 350-600 degrees C temperature range is believed to proceed via a carbonization process where the residual solid (char) undergoes a chemical transformation and rearrangement to give a more condensed polycyclic aromatic structure that upon further heating evolves PAH moieties. Extraction of tobacco with water led to a two fold increase in the yields of most PAHs studied. The extraction process removed low temperature non-PAH-forming components, such as alkaloids, organic acids and inorganic salts, and concentrated instead (on a per unit weight basis) tobacco components such as cell wall bio-polymers and lipids. Hexane extraction of the tobacco removed lipophilic components, previously identified as the main source of PAH precursors, but no change in PAH yields was observed from the hexane-extracted tobacco. Tobacco cell wall components such as cellulose, hemicellulose, and lignin are identified as major low temperature PAH precursors. A link between the formation of a low temperature char that evolves PAHs upon heating is established and the observed ng/g yields of PAHs from tobacco highlights a low temperature solid phase formation mechanism that may be operable in a burning cigarette.     

Expression of cytochromes P450 1A1 and 1B1 in human lung from smokers, non-smokers, and ex-smokers

Cytochromes P450 1A1 and 1B1 are known to bioactivate procarcinogens such as polycyclic aromatic hydrocarbons (PAHs) found in cigarette smoke and are inducible via an Ah receptor-mediated mechanism. The aim of this study was to examine the levels of expression of CYP1A1 and CYP1B1 in samples of lung from smokers (n = 18), non-smokers (n = 7), and ex-smokers (n = 7). Using immunoglobulin preparations of highly specific polyclonal antibodies and immunoblot analysis of microsomes from lung tissues, we determined the specific content for CYP1A1 and CYP1B1. For CYP1A1, we found median expression levels of 15.5 pmol/mg microsomal protein in smokers, 6.0 pmol/mg microsomal protein in non-smokers, and 19.0 pmol/mg microsomal protein in ex-smokers. The difference in median expression levels of smokers and ex-smokers compared to non-smokers was statistically significant. For CYP1B1, we found median expression levels of 1.8 pmol/mg microsomal protein in smokers, 1.0 pmol/mg microsomal protein in non-smokers, and 4.4 pmol/mg microsomal protein in ex-smokers. The difference in median expression levels between ex-smokers and non-smokers was statistically significant. These results suggest that levels of expression of CYP1A1 and CYP1B1 protein in lung tissues from smokers and ex-smokers are quantitatively greater than in non-smokers. By immunohistochemical analysis, we demonstrated the expression of CYP1A1 and CYP1B1 in normal human alveolar type I and II cells, ciliated columnar epithelial cells lining bronchoalveolar airways, and alveolar macrophages. These results confirm that CYP1A1 is expressed in normal human lung, appears to be induced in smokers, and show interindividual variation; the similar characteristics of CYP1B1 are demonstrated.     

Polycyclic aromatic hydrocarbons in commercial squids from different geographical origins: Levels and risks for human consumption

The concentrations of 18 polycyclic aromatic hydrocarbons (PAHs) were determined in five commercially valuable squid species from different geographical origins (Atlantic, Indic and Pacific Oceans). Out of the 18 quantified PAHs (the 16 PAHs considered by US EPA as priority pollutants, dibenzo(a,l)pyrene and benzo(j)fluoranthene) only dibenz(a,h)anthracene was not detected. The total concentrations of PAHs varied by a factor of more than 100-fold, from 0.22 (Loligo gahi) to 60.9 μg/kg ww (Loligo reynaudii). Intra- and inter-specific variability of PAH levels was statistically assessed. Nine carcinogenic (probable/possible) PAHs accounted for 1% (L. reynaudii) to 26% (Loligo opalescens) of the total PAHs content being the main contributors naphthalene (in Loligo duvaucelii, L. reynaudii and Loligo vulgaris species), chrysene (in L. opalescens) and indeno(1,2,3-cd)pyrene (in L. gahi). PAHs source analysis indicated that four of the five zones of capture of the different squid species are significantly affected by both petrogenic and pyrolytic sources. Assessment of the target carcinogenic risks, established by the US EPA, suggested that L. gahi (Atlantic Ocean) and L. opalescens (from Pacific Ocean) may pose additional risks for consumers, if not eaten in moderation, derived from benzo(a)pyrene ingestion.     

Different biological effects of PM2.5 from coal combustion,gasoline exhaust and urban ambient air relate to the PAH/metal compositions

Few studies have compared the biological effects of PM_2.5 from coal combustion, gasoline exhaust and urban ambient air, and the roles of polycyclic aromatic hydrocarbons (PAHs) and metals playing in the process remain unclear. In this study, PM_2.5 samples from coal combustion, gasoline exhaust and urban ambient air were analyzed for 16 PAHs and 23 metals. Cytotoxic and inflammatory effects of different PM_2.5 were evaluated on differentiated THP-1 and A549 cells, respectively. We found that the coal combustion PM_2.5 samples induced stronger cytotoxic and inflammatory effects (p < 0.05). Pearson’s correlation and principal component analysis showed that the PAHs containing four or more benzenoid rings and specific metals of cadmium, thallium, zinc and lead were positively related to the biological effects. Our results suggested that coal combustion PM_2.5 might be a more serious health hazard. Specific PAHs and metals might be account for the PM_2.5 induced biological effects.     

Predicting risk of low birth weight offspring from maternal features and blood polycyclic aromatic hydrocarbon concentration

Prenatal exposure to organic pollutants increases the risk of low birth weight (LBW) offspring. Women involved in the plucking of tea leaves can be exposed to polycyclic aromatic hydrocarbons (PAHs) during pregnancy through inhalation and diet. Therefore, the aim of the study was to investigate the association of maternal socio-demographic features and blood PAH concentration with LBW; also to develop a model for predicting LBW risk. The study was performed by recruiting 55 women who delivered LBW and 120 women with NBW (normal birth weight) babies from Assam Medical College. The placental tissue, maternal and cord blood samples were collected. A total of sixteen PAHs and cotinine were analysed by HPLC and GC-MS. Association of PAH concentration with weight was determined using correlation and multiple logistic regression analyses. Predictive model was developed using SVM^light and Weka software. Maternal features such as age, education, food habits, occupation, etc. were found to be associated with LBW deliveries (p-value<0.05). Overall, 9 PAHs and cotinine were detected in the samples. A multiple logistic regression depicted an increased likelihood of LBW by exposure to PAHs (pyrene, di-benzo (a,h) anthracene, fluorene and fluoranthene) and cotinine. Models based on the features and PAHs/ cotinine predicted LBW offspring with 84.35% sensitivity and 74% specificity. LBW prediction models are available at http://dev.icmr.org.in/plbw/ webserver. With machine learning gaining more importance in medical science; our webserver could be instrumental for researchers and clinicians to predict the state of the fetus.     

Environmental risk assessment for excipients from galenical pharmaceutical production in wastewater and receiving water

Many different excipients are used in galenical pharmaceutical production, in addition to the active pharmaceutical ingredients. Excipients are little investigated regarding their environmental fate and impact, even though some of them are used in appreciable quantities. For 35 excipients used in galenical production at Roche Basle and Roche Kaiseraugst, both in Switzerland, in the years 2013 and 2014, the environmentally relevant properties were collated. A predicted environmental concentration (PEC) was calculated for the wastewater treatment plants (WWTPs) and the receiving water, the River Rhine for both sites, based on maximum daily losses of the single excipients to wastewater, derived by mass balance, and the site-specific dilution factor. Predicted no effect concentrations (PNECs) were derived for the WWTPs and the River Rhine. PECs and PNECs were compared for the WWTPs and the receiving water, in an environmental risk assessment. Additionally, to simulate a worst case scenario, certain galenical productions where given excipients are used in the highest amounts were assumed to take place in parallel on the same day, resulting in theoretical maximum excipient losses to wastewater. All PEC/PNEC risk characterisation ratios for the excipients currently used by Roche in Switzerland are well below 1 throughout. Together with the fact that based on biodegradability data many excipients will be removed in the WWTP, this indicates that the excipients currently used do not present a risk to the environment.     

Comparative potency approach based on H2AX assay for estimating the genotoxicity of polycyclic aromatic hydrocarbons

Polycyclic Aromatic Hydrocarbons (PAHs) constitute a family of over one hundred compounds and can generally be found in complex mixtures. PAHs metabolites cause DNA damage which can lead to the development of carcinogenesis. Toxicity assessment of PAH complex mixtures is currently expressed in terms of toxic equivalents, based on Toxicity Equivalent Factors (TEFs). However, the definition of new TEFs for a large number of PAH could overcome some limitations of the current method and improve cancer risk assessment. The current investigation aimed at deriving the relative potency factors of PAHs, based on their genotoxic effect measured in vitro and analyzed with mathematical models. For this purpose, we used a new genotoxic assay (γH2AX) with two human cell lines (HepG2 and LS-174T) to analyze the genotoxic properties of 13 selected PAHs at low doses after 24 h treatment. The dose-response for genotoxic effects was modeled with a Hill model; equivalency between PAHs at low dose was assessed by applying constraints to the model parameters. In the two cell lines tested, we observed a clear dose-response for genotoxic effects for 11 tested compounds. LS-174T was on average ten times more sensitive than HepG2 towards PAHs regarding genotoxicity. We developed new TEFs, which we named Genotoxic Equivalent Factor (GEF). Calculated GEF for the tested PAHs were generally higher than the TEF usually used. Our study proposed a new in vitro based method for the establishment of relevant TEFs for PAHs to improve cancer risk assessment.     

Evaluation of polycyclic aromatic hydrocarbons (PAHs) in fish: a review and meta-analysis

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are a group of pollutants which occur in considerable amounts in the environment and food. In this study, a meta-analysis study was conducted on PAHs concentrations in fish in different parts of the world. The results showed that the PAHs were observed and quantified in fish in the most considered studies. The maximum and minimum concentration of PAHs was found in Cynoglossus Bilineatus fish of Persian Gulf (3970?ng/kg) and Cyprinus Carpio fish of Caspian Sea (0.004?ng/kg), respectively. These values are below the maximum value currently allowed by European Union regulations (12.0?μg/kg wet weight).     

Comparison of polycyclic aromatic hydrocarbons (PAHs) between smoked marc spirits and whiskies.

The presence of polycyclic aromatic hydrocarbons (PAHs) in three brands of smoked marc spirits, the only actually on the market, was studied and compared with literature PAHs concentrations reported for whiskies. In two brands of smoked marc spirit the higher-molecular-weight PAHs concentrations (5 and 6 rings PAHs) resulted higher (0.09-0.3 microg L (-1)) than in whiskies (0.00-0.02 microg L(-1)) and consequently higher resulted the carcinogenic potential expressed using the toxicity equivalent factor (TEF).     

Effect of charcoal types and grilling conditions on formation of heterocyclic aromatic amines (HAs) and polycyclic aromatic hydrocarbons (PAHs) in grilled muscle foods

Grilling muscle foods involves high temperatures that lead to production of cooking toxicants, such as heterocyclic aromatic amines (HAs) and polycyclic aromatic hydrocarbons (PAHs). To obtain realistic exposure levels of these two groups of mutagens analyses of the same samples using similar separation/detection techniques were performed. HAs and PAHs were quantified in well-done meat and fish samples grilled with wood and coconut shell charcoal at 200 °C. Quantitative HAs and PAHs profiles were different for beef and salmon using the same type of charcoal. Higher levels of HAs and PAHs were found in salmon samples. No significant differences were observed for HAs and PAHs in beef samples grilled with both charcoal types, whereas salmon grilled with coconut shell charcoal presented significantly lower amounts of HAs and PAHs than salmon grilled with usual wood charcoal. Continuous barbecuing with the same charcoal shown that combustion of fat that dropped along the grilling period contributed to higher formation of HAs and PAHs. Special attention must be given to the intake of barbecued foods since high amounts of HAs and PAHs can be taken in a single meal.     

Testing of different plants to determine influence of physico–chemical properties and contaminants content on municipal sewage sludges phytotoxicity

This study attempts to evaluate the Phytotoxkit? as a tool for measuring the toxicity of municipal sewage sludges using 10 common plants: mustard, turnip, cress, red clover, cucumber, tomato, radish, sorrel, and spinach. The results were used to determine a germination index (GI) and a median effective concentration (EC) value for each plant. The trace metal and polycyclic aromatic hydrocarbon (PAH) contaminant content and the physical–chemical properties were examined. Most sewage sludges were characterized by an unfavorable electrical conductivity value of about 5.2 mS/cm^?1. The most abundant trace metals were zinc (Zn) at 871–1680 mg kg^?1, manganese (Mn) at 245–661 mg kg^?1, and copper (Cu) at 88.2–161.0 mg kg^?1. The lowest values were determined for cobalt (Co) at 2.9–3.8 mg kg^?1 and cadmium (Cd) at 0.7–3.7 mg kg^?1. The PAH sum was based on 10 individual compounds (USE EPA), and the PAH content ranged from 4.76 to 27.95 mg kg^?1, most of the sewage sludges showing a predomination by carcinogenic PAHs. The GI values, based on seed germination and root growth inhibition bioassays, showed increasing plant sensitivity to the tested sewage sludges in the following order: cress > turnip > mustard > sorrel > tomato > sorgo > red clover > radish > cucumber > spinach. The EC50 sewage sludge values lay in the range 31–404 g/kg of soil, and significant relationships were found for most of the plants between EC50 and the magnesium content (Mg²⁺: α = 0.888–0.924, P = 0.05), calcium content (Ca²⁺: α = 0.813–0.911, P ≤ 0.05), and pH (α = ?0.913–0.948, P = 0.05). In the case of sewage sludge pollutants, significant relationships were found for trace metals such as: strontium (Sr: α = 0.851–0.948, P ≤ 0.05), chromium (Cr: α = 0.858, P ≤ 0.05), and nickel (Ni: α = 0.955, P = 0.05), as well as pyrene (PAHs). © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010.     

Formation of carcinogenic and inactive chrysene metabolites by rat liver microsomes of various monooxygenase activities

Microsomal oxidation of chrysene in rat liver occurs at various positions (1,2-; 3,4-; 5,6-). This has been verified by means of gas chromatography/mass spectrometry (GC/MS) and comparison with synthetic reference substances. After various rat pretreatments with inducers of the monooxygenase system the oxidation at the 3,4-position predominated in isolated microsomes. The formation of the ultimate carcinogen of chrysene—1, 2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydrochrysene — was not detectable in untreated rats. However, it was observed as 1,2,3-trihydroxy-1,2,3,4-tetrahydrochrysene-TMS-ether formed under workup and derivatisation conditions after pretreating the rats with phenobarbital, polychlorinated biphenyl, benzoflavone, or various polycyclic aromatic hydrocarbons. Polychlorinated biphenyls and benzoflavone were the most potent inducers for the formation of this metabolite.Abbreviations BjF Benzo(j)fluoranthene - BNF 5,6-benzoflavone - GC gas-liquid chromatography - HPLC high-pressure liquid chromatography - MS mass spectrometry - PAH polycyclic aromatic hydrocarbons - PCB polychlorinated biphenyl - TCBP 3,3,4,4-tetrachlorobiphenyl - TMS trimethylsilyl Assessment of environmental compounds by carcinogenspecific tests, part 1     

Comparative survey of PAHs incidence in Portuguese traditional meat and blood sausages

Sixteen polycyclic aromatic hydrocarbons (PAHs) in representative traditional sausages produced in “Trás-os-Montes” and “Alentejo”, were determined. Light PAHs represented similar overall contents in both regions and showed close decreasing order patterns (ACY, PHE, FLR and NAP), irrespective of the product type considered. Amongst the carcinogenic/mutagenic PAHs analyzed (PAH8), both regions also had greater contents associated to BaA and CHR, with slightly higher values for the former compound in “Alentejo” and, oppositely, for the later in “Trás-os-Montes”. However, their quantitative comparison showed that the general mean total PAH content found in “Trás-os-Montes” was almost 3-fold higher than in similar products from “Alentejo” and this factor was about 8-fold superior when the PAH8 and PAH4 indicators were compared, expressing benzo[a]pyrene toxic equivalencies (BaPE), 15 times (total mean toxicity), 34 times (PAH8) and 9 times (PAH4) higher. In general terms, the mean BaP content of all analyzed samples from “Alentejo” was 0.41 μg kg⁻¹. Differently that value in “Trás-os-Montes” reached 3.57 μg kg⁻¹, expressing concerning average contents of 5.35, 5.87 and 4.51 μg kg⁻¹ in Chouriço de Carne, Moura and Salpicão sausages, respectively.     

Mutagenicity testing in the Salmonella typhimurium assay of phenolic compounds and phenolic fractions obtained from smokehouse smoke condensates

Smokehouse smoke, which is used for flavouring meat products, was investigated for its mutagenic activity in the Salmonella typhimturium assay. We chiefly concerned with the fractions free of polycyclic aromatic hydrocarbons but containing phenol compounds, which are responsible for the preservative and aromatizing properties of the smoke. The most abundantly occurring phenol compounds (phenol, cresols, 2,4-dimethylphenol, brenzcatechine, syringol, eugenol, vanilline and guaiacol) gave negative results when they were tested for mutagenicity at five concentrations up to 5000 μg/plate, with and without S-9 mix, using five strains of S. typhimurium. Even when phenol was further investigated in a variety of test conditions, no induction of his⁺ revertants was observed. When smokehouse smoke was condensed and fractionated the majority of the various phenolic fractions also gave negative results when tested at five concentrations using five strains of S. typhimurium. However there was a slight increase in the number of revertants in a few cases. The presence in the phenolic fractions of very small amounts of mutagenic impurities, the nature of which needs further investigation, cannot be excluded. These results support the further development of non-hazardous smoke-aroma preparations, based on the phenolic components of smokehouse smoke.     

Quality characteristics and safety of smoke-flavoured water.

Smoke-flavoured water is produced in Ghana by filling a previously smoked container with potable water and allowing the water to condition with the smoke to attain a characteristic rain water flavour. Owing to the current knowledge on the toxicity, carcinogenicity and other safety issues of some smoke-constituents, the commercial production of the product is becoming a public health concern. This study sought to determine the effects of the smoke-flavouring process on the quality characteristics of smoke-flavoured water to predict the safety of the product. A traditional and a commercial protocol for the production of smoke-flavoured water were simulated in the laboratory and at the site of a company which used to produce the product, respectively. Samples of the flavoured water produced were analyzed for pH, colour, turbidity, conductivity, total hardness, dissolved oxygen content (DO), biochemical oxygen demand (BOD), the polycyclic aromatic hydrocarbon constituents (PAHs), coliform count, and flavour acceptability. Data obtained were evaluated in reference to data on control samples prepared during the investigations. The results obtained suggested that the smoke-flavouring process may not significantly change most of the physico-chemical and microbiological characteristics of the water processed, and thus not affect the drinking quality characteristics of the water. The process however has the potential of adding some organic compounds, which could include polycyclic aromatic hydrocarbons (PAHs), the group that may have the toxicity and carcinogenic effects. The types of PAHs and their concentrations are expected to vary with the process characteristics, but could be insignificantly low to affect the safety of the water. The results suggest a need for some standardization of the process.     

Toxicity and EROD-inducing potency of 24 polycyclic aromatic hydrocarbons (PAHs) in chick embryos

The toxicities (embryolethality) of 24 polycyclic aromatic hydrocarbons (PAHs) were determined in chick embryos using a 72-h test. The substances, dissolved in peanut oil, were injected into the air sacs of eggs preincubated for 7 days. LD₅₀ values were determined for the four most toxic of the 24 compounds. Benzo [k] fluoranthene proved to be the most potent, with an LD₅₀ of 14 g (56 nmol)/kg egg. Dibenz[a,h]anthracene, benz[a]anthracene and benzo[b]naphtho[2,3-d]thiophene were a few times less toxic [LD₅₀=39 g (140 nmol)/kg, 79 g (349 nmol)/kg and 82 g (350 nmol)/kg, respectively]. The LD₅₀ of benzo [k] fluoranthene was only about 5 times higher than that previously found for the most potent coplanar polychlorinated biphenyl (PCB), 3,3,4,4,5-pentachlorobiphenyl [LD₅₀=3.1 g (9.4 nmol)/kg], in the same kind of test. The toxicities of 18 of the PAHs in this study have also been evaluated previously using a 2-week test in chick embryos. Dibenz[a,h]anthracene, which had not been studied earlier in the 2-week test, proved to be almost as toxic as previously found for benzo [k] fluoranthene in that test. Several of the PAHs studied induced EROD activity in chick embryos, and, in general, the most toxic PAHs were also the most potent inducers of EROD. The highest enzyme activities were found after treatment with indeno[1,2,3-c,d]pyrene (12 times the control value) and dibenz[a,h]anthracene (8 times the control value). However, due to the high toxicity of dibenz[a,h]anthracene, the dose used was 7 times lower than that of indeno [1,2,3-c,d]pyrene. Following injection of PAHs on day 7, the EROD activities on day 10 were considerably lower than those obtained after a corresponding treatment with coplanar PCBs in an earlier study. Of the PAHs studied, some exhibited very high embryotoxicity. The most toxic PAHs induced EROD activity, suggesting that their toxicity was at least partly mediated via binding to the Ah receptor.