Current situation of polycyclic aromatic hydrocarbons (PAH) in PM2.5 in a receptor site in Mexico City and estimation of carcinogenic PAH by combining non-real-time and real-time measurement techniques.

Air pollution is a public health concern. Polycyclic aromatic hydrocarbons (PAH) are ubiquitous atmospheric pollutants contained in the atmospheric aerosol. PAH in particulate matter with diameters ≤2.5 µm (PM2.5) represent a human health risk due to their toxic properties. In this study, PAH in PM2.5 at a receptor site of Mexico City during the dry cold season were determined. The most abundant PAH (median, 10-90th percentile, pg m-3) were benzo[ghi]perylene (467, 291-697), followed by pyrene (427, 218-642). A decrease around 40% in the carcinogenic PAH onto PM2.5 was calculated with respect to the same PAH measured a decade ago, at the same receptor site, despite of increase in vehicle fleet. The PAH decrease trend agrees with the decrease trend of CO, NO and NO2, released into the air by similar emission sources than PAH. Control emissions strategies implemented by local and federal authorities are discussed. PAH analyses were carried out by non-real-time and real-time methods. The PAH non-real-time method involved PM2.5 sampling, sample treatment and gas chromatography-mass spectrometry analysis. The PAH real-time method involved the use of a photoelectric aerosol sensor (PAS). The PAH determination by non-real time method was selective and efficient, with recoveries between 75 ±â€¯14% and 98 ±â€¯26%. By combining non-real-time and real-time methodologies, multivariate regression models were obtained based on PAS response, NO2 and wind speed to estimate PAH in PM2.5 at low-cost (r2 = 0.59 to r2 = 0.89). Fossil fuel combustion from vehicles was the major source around the sampling site. Diagnostic ratios (DR) based on retene, chrysene, and triphenylene, suggested biomass burning emission sources. Photo-oxidation in sunny months was observed based on benzo[a]pyrene, benzo[ghi]perylene, benz[a]anthracene, indeno[1,2,3-cd]pyrene and black carbon. The correlation analyses suggested transport of PM2.5, O3, BC and SO2 to the sampling site, and local emissions of PAH, NO and CO.

An innovative ultrasound assisted extraction micro-scale cell combined with gas chromatography/mass spectrometry in negative chemical ionization to determine persistent organic pollutants in air particulate matter.

New clean technologies are needed to determine concentration of organic pollutants without generating more pollution. A method to extract Persistent Organic Pollutants (POPs) from airborne particulate matter was developed using a novel technology recently patented called ultrasound assisted extraction micro-scale cell (UAE-MSC). This technology extracts, filters, collects the sample, and evaporates the solvent, on-line. No sample transfer is needed. The cell minimizes sample manipulation, solvent consumption, waste generation, time, and energy; fulfilling most of the analytical green chemistry protocol. The methodology was optimized applying a centred 23 factorial experimental design. Optimum conditions were used to validate and determine concentration of 16 organochlorine pesticides (OCls) and 6 polybrominated diphenyl ethers (PBDEs). The best conditions achieved were 2 extractions with 5mL (each) of dichloromethane over 5min (each) at 60°C and 80% ultrasound potency. POPs were determined by gas chromatography/mass spectrometry in negative chemical ionization (GC/MS-NCI). Analytical method validation was carried out on airborne particles spiked with POPs at seven concentration levels between 0.5 and 26.9pgm-3. This procedure was done by triplicate (N=21). Recovery, ranged between 65.5±2.3% and 107.5±3.0% for OCls and between 79.1±6.5% and 105.2±3.8% for PBDEs. Linearity (r2) was ≥0.94 for all compounds. Method detection limits, ranged from 0.5 to 2.7pgm-3, while limits of quantification (LOQ), ranged from 1.7 to 9.0pgm-3. A Bias from -18.6% to 9% for PBDEs was observed in the Standard Reference Material (SRM) 2787. SRM 2787 did not contain OCls. OCls recoveries were equivalent by UAE-MSC and Soxhlet methods UAE-MSC optimized extraction conditions reduced 30 times less solvent and decreased the extraction time from several hours to ten minutes, respect to Soxhlet. UAE-MSC was applied to 15 samples of particles less than 2.5µm (PM2.5) from three seasons (warm dry, rainy, and cold dry) collected in five sites around Mexico City. OCls (4,4'-DDE and endrin aldehyde) concentrations ranged from

Organochlorine pesticide residue levels in blood serum of inhabitants from Veracruz, Mexico.

The objective of the present study was to monitor the levels of organochlorine pesticides HCB; α-, ß-, γ-HCH; pp'DDE; op'DDT; and pp'DDT in blood serum of Veracruz, Mexico inhabitants. Organochlorine pesticides were analyzed in 150 blood serum samples that constituted that which remained after clinical analyses, using gas chromatography-electron-capture detection (GC-ECD). The results were expressed as milligrams per kilogram on fat basis and micrograms per liter on wet weight. Only the following pesticides were detected: p,p'-DDE was the major organochlorine component, detected in 100% of samples at mean 15.8 mg/kg and 8.4 µg/L; p,p'-DDT was presented in 41.3.% of monitored samples at mean 3.1 mg/kg and 1.4 µg/L; ß-HCH was found in 48.6% of the samples at mean 4.9 mg/kg and 2.7 µg/L; op'DDT was determined to be in only 3.3% of monitored samples at mean 2.7 mg/kg and 1.4 µg/L. The pooled samples divided according to sex showed significant differences of ß-HCH and pp'DDE concentrations in females. The samples grouped according to age presented the third tertile as more contaminated in both sexes, indicating age as a positively associated factor with serum organochlorine pesticide levels in Veracruz inhabitants.

Organochlorine pesticide gradient levels among maternal adipose tissue, maternal blood serum and umbilical blood serum.

The objective of the present study was to determine levels and calculate ratios of copartition coefficients among organochlorine pesticides ß-HCH, pp'DDE, op'DDT and pp'DDT in maternal adipose tissue, maternal blood serum and umbilical blood serum of mother-infant pairs from Veracruz, Mexico. Organochlorine pesticides were analyzed in 70 binomials: maternal adipose tissue, maternal serum and umbilical cord serum samples, using gas chromatography with electron capture detection (GC-ECD). The results were expressed as mg/kg on fat basis. p,p'-DDE was the major organochlorine component, detected in every maternal adipose tissue (0.770 mg/kg), maternal serum sample (5.8 mg/kg on fat basis) and umbilical cord blood sample (6.9 mg/kg on fat basis). p,p'-DDT was detected at 0.101 mg/kg, 2.2 mg/kg and 5.9 mg/kg respectively, according to the order given above. ß-HCH was detected at 0.027 mg/kg, 4.2 mg/kg and 28.0 mg/kg respectively. op'DDT was detected only in maternal adipose tissue at 0.011 mg/kg. The copartition coefficients among samples identify significant increases in concentrations from adipose tissue to maternal blood serum and to umbilical blood serum. The increase indicated that maternal adipose tissue released organochlorine pesticides to blood serum and that they are carried over to umbilical cord blood.

Comparison of organochlorine pesticide levels in human adipose tissue of inhabitants from Veracruz and Puebla, Mexico.

Since the discovery of insecticide properties of DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) and HCH (hexachlorocyclohexane), they have provided great benefits to humans in sanitary actions to combat the spread of infection-borne disease vectors. Public Health Programs in Mexico used DDT and HCH until 1999 as the insecticides of choice to control disease-transmitting organisms. Because of their persistence and accumulative properties, organochlorine pesticides bioconcentrate in lipids of the human body, reflecting the rate of environmental exposure. Eighty human abdominal adipose tissue samples from Veracruz and 80 samples from Puebla were analyzed and the obtained results were compared among both populations. The results from Veracruz showed higher contamination levels (mg/kg on lipid base) compared to Puebla: beta-HCH, 0.072 vs. 0.029; pp'DDE (Dichlorodiphenyldichloroethylene), 2.364 vs. 0.726; op'DDT, 0.022 vs. 0.025; pp'DDT, 0.192 vs. 0.061; and Sigma-DDT, 2.589 vs. 0.806. The population from Veracruz and from Puebla divided by sex, origin, and cause of death presented no statistical differences. The comparison between sexes (women and men groups) at Veracruz and Puebla indicated significantly higher levels in Veracruz and statistical significant differences. Calculating possible risks (odds ratios, OR), pp'DDE (OR = 5.04) and op'DDT (OR = 2.93) revealed significantly higher risk for the Veracruz population. The study indicated prolonged DDT exposure of Mexicans caused by the past sanitary use and persistence of its residues in soils and air.

Breast milk excretion Kinetic of b-HCH, pp'DDE and pp'DDT.

Breast milk is considered the most important route in the elimination of deposited organochlorine pesticides in a mother's body. The equilibrium of organochlorine pesticides in the human body considers the elements of internal transport processes, the equilibrium pattern between pesticides and tissue fat contents, and the mobilization of lipids and lipoproteins among body parts. The aim of this study was to determine organochlorine pesticide levels in breast milk samples from the 4th to the 30th day of lactation and the trend in their concentration time so as to forecast the time tendency of residue levels and the pesticide excretion pattern. Milk samples were taken from forty participants and analyzed by GLC-ECD. The organochlorine pesticide residues determined in the breast milk samples during lactation decreased: ß-HCH from 0.095 to 0.066 mg/kg, pp'DDE from 1.807 to 1.423 mg/kg and pp'DDT from 0.528 to 0.405 mg/kg, at the characteristic rate for each compound. The obtained results compared with the calculated fits of forecasts were parallel and did not exhibit significant differences. The newborn baby exposed during lactation had organochlorine pesticide residues whose levels decreased permanently. The levels depended not only on the breast milk nutrition, but also on the total environmental exposures which included air pollution as a significant contamination source.

DDT and HCH isomer levels in soils, carrot root and carrot leaf samples.

Agricultural cultivation assists organochlorine pesticide migration from contaminated soils to growing plants. This phenomenon is caused by retention processes that modify volatile pesticide exchange between soil, air and plants. The aim of the study was to monitor organochlorine pesticide (HCB, alpha- and gamma-HCH, pp'DDE, op'DDT, pp'DDT) levels and compare these concentrations in soil, carrot roots and carrot leaves. Fifty soil samples, 50 carrot root and 50 carrot leaf samples were taken from the same fields and analyzed by GLC-ECD. The results reveal organochlorine pesticide diffusion from agricultural soils to growing carrot plants and their vapors adsorption by leaves. Within the carrot plant, organochlorine pesticides accumulate especially in carrot root peel, 3-7 times more than in root flesh.

Cell proliferation kinetics and genotoxicity in lymphocytes of smokers living in Mexico City.

Genotoxicity caused by tobacco smoke was assessed in peripheral blood lymphocytes of smokers living in Mexico City by determining sister chromatid exchange (SCE), cell proliferation kinetics (CPK), replication index (RI) and mitotic index (MI). Nicotine levels, and its major metabolite cotinine, were also estimated in urine samples using gas-chromatography-mass spectrometry to quantify smoking intensity. The outcome of the analysis and the comparison of the 77-smoker group with a non-smoking control group showed that moderate and heavy smokers exhibited significant differences (P < 0.001 and P < 0.05, respectively) in CPK, with an underlying delay in the cellular cycle; similarly, RI was significantly different in these groups (P < 0.001 and P < 0.0001, respectively). There were significant correlations (P < 0.05) between age and number of years the subject had been smoking, as well as between RI and nicotine and cotinine levels and between CPK (M1, M2 and M3) and nicotine and cotinine levels. Smokers were classified for the analysis according to the nicotine levels (it is in relation to number of cigarettes smoked per day) found in urine (ng/mL) as: light (10-250), moderate (251-850) and heavy (851-4110). Significant differences in CPK were found (P < 0.05) between moderate and heavy smokers and non-smokers. Significant differences in RI were found between moderate (P < 0.001) and heavy smokers (P < 0.0001) and non-smokers, but not for the light smoking group. MI was determined in 57 of the smokers, whereas SCE frequency was only recorded in 34 smokers. Both parameters yielded no significant differences, nor correlations with any of the assessed variables. In conclusion, cytokinetic and cytostatic effects were mainly detected in heavy and moderate smokers. Cell cycle delay and RI decrease were found in all ;healthy' smokers. The nicotine and cotinine exposure (causing oxidative damage to DNA) may have implications in the decrease in cell replication due to direct damage to DNA and/or a decrease in the DNA repair mechanisms. Alternatively, nicotine and cotinine may possibly induce apoptosis.

Persistent organochlorine pesticide levels in bovine fat from Mexico.

Organochlorine pesticides have been used in Mexico in agriculture as a seed dresser, in sanitation, in malaria control programmes and in livestock to combat ectoparasites. The pesticides applied drift to areas where cattle graze and plants grow. Because of their chemical stability, they accumulate in the lipid-rich tissues of the body. In the body, they circulate throughout all compartments and accumulate in adipose fat. The aim was to monitor the organochlorine pesticide levels in bovine muscle fat and kidney fat from cows living in an endemic malaria zone, where the environmental contamination can be suspected as being higher. Two hundred samples (100 muscle fat, 100 kidney fat) were analysed by gas chromatography. From the pesticides, only hexachlorobenzene (HCB), beta-hexachlorocyclohexane (HCH), gamma-HCH, pp'-1.1.1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT), op'-DDT and pp'-DDE, were detected frequently and at levels above the detection limits. The HCB mean level was low at 0.009 mg kg(-1) on a fat basis. From the HCH isomers, beta-HCH mean concentration was 0.039 mg kg(-1) and gamma-HCH was 0.025 mg kg(-1) on a fat basis. Among DDTs, pp'-DDT was the major constituent (0.032 mg kg(-1) on a fat basis) followed by pp'-DDE (0.025 mg kg(-1) on a fat basis) and op'-DDT (0.023 mg kg(-1) on a fat basis). The DDT total (sigma DDT) level was 0.067 mg kg(-1) on a fat basis. Comparing the previous study (1994) and the present one (2002-03), organochlorine pesticide levels were decreased. HCB decreased 3.7 times from 0.033 to 0.009 mg kg(-1) on a fat basis; beta-HCH decreased 3.8 times from 0.149 to 0.039 mg kg(-1) on a fat basis; pp'-DDE did not reveal a significant difference at 0.026 versus 0.025 mg kg(-1) on a fat basis. However, pp'-DDT decreased substantially, 6.7 times from 0.215 to 0.032 mg kg(-1) on a fat basis. The DDT total decreased 3.5 times from 0.236 to 0.067 mg kg(-1) on a fat basis. The tendency for reduced concentrations in organochlorine pesticide levels in Mexican cows is caused by their substitution with pyrethroids used in agriculture and by the Mexican Ministry of Health in sanitary programmes.

Persistent organochlorine pesticides in Mexican butter.

Organochlorine pesticides have been used in Mexico in malaria control programmes against ectoparasites and as seed dresser. Owing to their chemical stability, they tend to accumulate in the lipid part of the organisms. The stored pesticides are excreted with the endogenous fat during milk production. The aim was to monitor the organochlorine pesticide levels in butter manufactured in Mexico. From the pesticides, only HCB, beta-HCH, pp'-DDT, op'-DDT and pp'-DDE with major frequency and levels were detected. The HCB mean level was low at 0.008 mg kg(-1) on a fat basis. From the HCH isomer, only the beta-HCH at 0.065 mg kg(-1) on a fat basis was determined, remaining as the main contaminant of the monitored butters. Among DDTs, pp'-DDE was the major constituent (0.043 mg kg(-1) on a fat basis) followed by pp'-DDT (0.036 mg kg(-1)) and op'-DDT (0.009 mg kg(-1)). Comparing the previous study (1994) and this one (2001), all organochlorine pesticides had a descendent tendency; beta-HCH decreased from 0.095 to 0.065 mg kg(-1) on a fat basis, whereas the total DDT decreased from 0.056 to 0.047 mg kg(-1), pp'-DDT from 0.050 to 0.036 mg kg(-1), op'-DDT from 0.018 to 0.009 mg kg(-1), while pp'-DDE increased from 0.032 to 0.043 mg kg(-1). The decreased DDT levels in Mexican butters is caused by the substitution of organochlorine insecticides with pyrethroids used by the Mexican Ministry of Health since 1999 in sanitary programmes.

Persistent organochlorine pesticide levels in cow's milk samples from tropical regions of Mexico.

Organochlorine pesticides have been used in agriculture as a seed dresser, in sanitation, in malaria control programmes and in livestock to combat ectoparasites. Their residues accumulate in lipid-rich tissues due to their chemical stability and persistence. In the body they circulate throughout all compartments, deposit themselves in adipose fat and can be excreted during lactation. These pesticides are applied in tropical zones and drift to areas where cattle graze. Therefore, analyses of cow's milk samples can serve as an indicator of environmental and cows' exposure to them. One hundred and fifty milk samples were taken each year in 1998 and 2001 and analysed to determine concentrations of HCB, beta-HCH, pp"-DDE, op'-DDT and pp'-DDT. Results obtained indicate that beta-HCH is one of the main contaminants (0.106 and 0.087 mg x kg(-1) on fat basis) followed by pp'-DDT (0.078 and 0.037 mg x kg(-1) on fat basis) and pp'-DDE (0.051 and 0.033 mg x kg(-1) on fat basis). The HCB and op'-DDT were detected in lower quantities respectively (0.008 and 0.006 mg x kg(-1), and 0.031 and 0.010 mg x kg(-1) on fat basis). When comparing the results obtained with those from the previous study, it was noted that DDT levels decreased significantly in 2001 as a result of the substitution of the organochlorine insecticides with pyrethroids sprayed by the Mexican Ministry of Health to combat malaria since 1999.

Metabolic activation of three arylamines and two organophosphorus insecticides by coriander (Coriandrum sativum) a common edible vegetable.

Organophosphorus insecticides and arylamines, widely distributed in the environment, can be activated into mutagens by plants. Plant activation of three aromatic amines, 4-nitro-o-phenylenediamine (NOP), m-phenylenediamine (m-PDA) and 2-aminofluorene (2AF), and two organophosphorus insecticides, dimethoate and methyl parathion has been the focus of this study. The plant cell/microbe coincubation assay was used employing coriander (Coriandrum sativum) suspended cell cultures as the activating system. Interestingly, this vegetable is included in the Mexican diet and ingested generally uncooked and could have epidemiological consequences. As a genetic end point, the Salmonella typhimurium tester strain TA98 was used. Protein contents, as well as peroxidase activity and peroxidase activity inhibited by diethyldithiocarbamate (DEDTC) of coriander cultures were determined after the coculture. Coriander cells highly activated three aromatic amines, NOP, m-PDA and 2-AF to mutagenic products detected in Salmonella. On the other hand, insecticides were only lightly activated, probably because peroxidase activity of coriander cells was inhibited, corroborated by DEDTC peroxidase inhibition. In all the assays, NOP was the more potent mutagenic compound. The results demonstrated that coriander cells were metabolically competent and suitable for a plant cell microbe coincubation assay, developed to analyze the promutagen activation by plant systems and can be used as a indicator of potential genetic effects.

Cytogenetic biomonitoring in a Mexican floriculture worker group exposed to pesticides.

The cytogenetic damage in floriculturists of Morelos State, Mexico, exposed to pesticides, was evaluated by mean of biological tests based on sister chromatid exchanges (SCE) in lymphocytes of peripheral blood and micronuclei (MN) in exfoliated cells of the buccal mucosa. Besides the cytogenetic analysis, the effects of pesticides exposure on the cell proliferation kinetics (CPK) by the replication index (RI) were also studied. The mitotic index (MI) to detect cytotoxic effects was also determined. Greenhouses of the towns of Santa Catarina, Jiutepec and Yecapixtla were selected for the study, because the application of chemicals to the flowers is uncontrolled. As non-exposed group, people of the town of Temisco were chosen; their activity was not related to pesticides. The SCE were analyzed in the peripheral blood of 30 persons, 22 women and 8 men, with 10 and 1.5 years of exposure to pesticides, respectively, and of 30 persons, 28 women and 2 men, that were considered as the non-exposed group. Samples of buccal mucosa were also taken from each person. Significant differences between exposed and non-exposed groups were found in SCE, CKP and MI. Besides, the MN frequencies in the exposed group were three times higher than in the non-exposed group.

Genetic effects observed in tetrads of Tradescantia induced by radon.

Inflorescences of Tradescantia clone 4430 were exposed to different concentrations of radon (Rn) gas (0.85, 12.10, 36.50 and 98.16 kBq/m3) from plants placed in an acrylic chamber that received radon from a container with pitchblende (containing uranium mineral). The exposure time was 24 h, afterwards the plants were left for 6 h in water and constantly aerated. Positive control plants were irradiated with gamma rays (0.8 Gy) and negative control plants received ambient air only (the background measurement had a mean of 0.38 kBq/m3). Micronuclei (MCN) in the tetrads induced by alpha particles emitted from Rn were tabulated and a linear concentration response was obtained. The potency of radon to induce MCN from the slope of the regression line was 0.13 MCN/kBq/m3 of alpha-radiation. Radon could reach the anthers by diffusion through the aerial spaces within the buds.

Genotoxicity of organic extracts of airborne particles in somatic cells of Drosophila melanogaster.

Complex mixtures extracted from air filters exposed for 24 h in two sessions (27 July and 02 August 1991) and at two locations (Merced, downtown, and Pedregal de San Angel, south-west) in Mexico City were analysed. The organic extracts were from airborne particles equal or smaller than 10 microns (PM10), and from total suspended particles (TSP). These organic extracts were assayed in the somatic mutation and recombination test (SMART) in wings of Drosophila melanogaster using two different crosses as well as in the Salmonella/microsome assay using strain TA98 with and without S9 fraction. The presence of polycyclic aromatic hydrocarbons (PAH) in the extracts was determined by gas chromatography. The genotoxic activities observed in the two test systems were comparable with the indirect mutagens producing greater response than the direct mutagens. The quantities of particulate matter as well as the genotoxic activities were higher on 02 August than on 27 July 1991 for both locations. The amounts of airborne particles and the resulting genotoxic activities were higher at Merced than at Pedregal. In both biological systems, PM10 were more genotoxic than TSP. These results demonstrate the sensitivity of the Drosophila wing SMART-which is an in vivo eukaryotic genotoxicity assay-as a biological monitor of environmental pollution related to airborne particles.

In vivo and in vitro promutagen activation by Vicia faba of thiocarbamate herbicides molinate and butylate to products inducing sister chromatid exchanges in human lymphocyte cultures.

Molinate and butylate treatments for 4 h of Vicia faba root tip meristems, showed that both thiocarbamate herbicides increased significantly SCE frequency. Direct treatments of molinate and butylate on human lymphocytes applied 24 h after the beginning of culture did not induce SCE. When S10 extracts of the Vicia roots, treated for 4 h with molinate and butylate (in vivo activation) were added to lymphocytes (24 h after of the beginning of culture), SCE were induced in a concentration-response manner. The in vitro assays, in which molinate and butylate was added at 48 h lymphocyte cultures for 4 h, showed a negative response, however, in the treatment where the S10 metabolic mix was added the SCE frequencies were significantly different to the control, and the concentration-response relationship was not observed with molinate, but it was obtained with butylate. The results showed that both herbicides needed the V. faba metabolism to produce SCE in human lymphocyte culture.

Sister chromatid exchanges in Vicia faba induced by arsenic-contaminated drinking water from Zimapan, Hidalgo, Mexico.

Sister chromatid exchanges (SCE) in Vicia faba root tips were used to examine well water containing high levels of arsenic. The increased amount of arsenic was contained in well water from different towns of Zimapan, Hidalgo, Mexico. Treatments of 3 h were applied followed by the differential staining technique of Tempelaar et al. (Mutation Res. 103 (1982) 321-326). Concentrations of arsenic from 0.267 up to 1.070 mg/l were determined by colorimetry in the polluted samples used for this study. These values were above the permissible limit of 0.05 mg/l in drinking water. In all cases, except one in which the As concentration was 0.021, the arsenic-contaminated water produced significant increases of SCE compared with the control (p < 0.001) and a concentration-response relationship was observed. The SCE potency factor of 33 per mg/l of arsenic was calculated as the slope of a common regression line, pooling data previously obtained in the Comarca Lagunera and the results observed in Zimapan.

Genotoxic activity of environmentally important polycyclic aromatic hydrocarbons and their nitro derivatives in the wing spot test of Drosophila melanogaster.

The genotoxicity of three polycyclic aromatic hydrocarbons (PAHs) and of three of their nitro derivatives was evaluated in the wing Somatic Mutation And Recombination Test (SMART) in Drosophila melanogaster. Two crosses were used, i.e. the standard cross (ST) and the improved high bioactivation cross (HB) which is characterised by an increased sensitivity to the genotoxic effects of promutagens and procarcinogens. Larvae trans-heterozygous for the two recessive wing cell markers multiple wing hairs (mwh) and flare (flr3) were fed with the test compounds for 48 h. The wings of the surviving flies were analysed for the occurrence of single and twin spots. Naphthalene, 1-nitronaphthalene and 1,5-dinitronaphthalene proved to be more genotoxic in the HB cross than in the ST cross. Anthracene showed a clear genotoxic activity only in the HB cross whereas it was negative in the ST cross. 9-Nitroanthracene gave inconsistent results in both crosses. Phenanthrene was negative in the ST cross, but weakly positive in the HB cross. These results demonstrate that the genotoxic activity of these PAHs and their nitro derivatives can be detected with the somatic cells of the wing imaginal discs of larvae with high bioactivation capacity.