Marta Adonis

Susceptibility and exposure biomarkers in people exposed to PAHs from diesel exhaust

Xenobiotic metabolizing enzymes, especially CYP1A1 and GSTM1, are involved in the activation and conjugation of PAHs and are controlled by polymorphic genes. PAHs released from diesel emissions in many cities of the world, especially in developing countries, contribute significantly to the toxic effects of airborne inhalable particles. We have evaluated the gene-environment interaction in Santiago of Chile, studying the contribution of CYP1A1 and GSTM1 polymorphisms on 1-OH-P urinary levels used as the PAHs exposure biomarker. The study was performed on 59 diesel exposed (38 diesel revision workers and 21 subjects working in an urban area as established street vendors) and 44 non-exposed subjects living in a rural area. The 1-OH-P urinary levels of the urban (P=0.043) and rural (P=0.040) populations showed, without considering the genotypes, significant differences between smokers and non-smokers, but no significant differences were found between smokers and non-smokers among the diesel plant workers (P=0.33). Non-smoking subjects of the diesel plants and the urban area showed similar 1-OHP levels (P=0.466) which were significantly higher than those of the subjects living in the rural area (P<0.05). When 1-OH-P levels were related with genotypes, an association was observed for the CYP1A1*2A genotype, so that the diesel-exposed workers carrying the CYP1A1*2A allele showed significantly higher 1-OH-P levels than the subjects from the rural area with the same genotype (P=0.008). On the other hand, there was no significant correlation between urinary 1-OH-P levels and GSTM1 null genotype, although higher levels of the urinary metabolite were found in individuals carrying the combined CYP1A1*2A and GSTM1 null genotype (P=0.055). These results may suggest an association between levels of the exposure biomarker 1-OH-P and presence of the CYP1A1*2A genotype, a potential genetic susceptibility biomarker which might be useful in identifying individuals at higher risk among people exposed to high PAH levels in diesel exhaust.

Arsenic Biotransformation as a Cancer Promoting Factor by Inducing DNA Damage and Disruption of Repair Mechanisms

Chronic exposure to arsenic in drinking water poses a major global health concern. Populations exposed to high concentrations of arsenic-contaminated drinking water suffer serious health consequences, including alarming cancer incidence and death rates. Arsenic is biotransformed through sequential addition of methyl groups, acquired from s-adenosylmethionine (SAM). Metabolism of arsenic generates a variety of genotoxic and cytotoxic species, damaging DNA directly and indirectly, through the generation of reactive oxidative species and induction of DNA adducts, strand breaks and cross links, and inhibition of the DNA repair process itself. Since SAM is the methyl group donor used by DNA methyltransferases to maintain normal epigenetic patterns in all human cells, arsenic is also postulated to affect maintenance of normal DNA methylation patterns, chromatin structure, and genomic stability. The biological processes underlying the cancer promoting factors of arsenic metabolism, related to DNA damage and repair, will be discussed here.

Mutagenicity of organic extracts from Santiago (Chile) airborne particulate matter.

The Ames test has been used to detect the mutagenic activity of organic extracts from Santiago (Chile) airborne particles collected in 1990 and 1991 in one of the monitoring net system stations (MACAM). The samples were assayed with the strains TA98, TA98-NR, and TA98/1,8-DNP6 of Salmonella typhimurium, in the presence and in the absence of liver S9 fraction obtained from rats treated with Aroclor 1254. With the strain TA98 all the samples showed a very high mutagenic response either in the presence or in the absence of S9 fraction, suggesting that Santiago airborne particles contain both indirect-acting (polycyclic aromatic hydrocarbons) and direct-acting mutagenic agents. The mutagenicity of Santiago airborne particles was much higher than that reported in studies performed in other countries. Results obtained with the strains TA98-NR and TA98/1,8-DNP6 suggest that the extracts also contain mononitro and dinitroarenes. These nitroarenes have been described as very potent mutagenic agents, that can be generated by photochemical reactions under certain atmospheric conditions, or in the combustion of fuel, especially of diesel motors. The presence of polycyclic aromatic hydrocarbons and nitroarenes in Santiago airborne particles, as well as the high levels of mutagenicity detected, suggest that the inhabitants permanent exposure to these kinds of compounds represents a high risk for human health.

CYP1A1 and GSTM1 genetic polymorphisms in lung cancer populations exposed to arsenic in drinking water

Region II of Chile is the most important copper mining area in the world and it shows the highest lung cancer mortality rate in the country (35/100 000). The population in Antofagasta, the main city of Region II, was exposed from 1958 to 1970 to 860 µg m−3 arsenic (As) in drinking water and has currently been declining to 40 µg m−3. Glutathione serves as a reducing agent and glutathione S-transferase (GST) may have an important role in As methylation capacity and body retention. In the current study, the null genotype of GSTM1 and the MspI polymorphism of CYP450 1A1 were investigated in lung cancer patients and in healthy volunteers of Region II. In males, the 2A genotype of MspI represented a highly significant estimated relative lung cancer risk (OR = 2.60). Relative lung cancer risk for the combined 2A/null GSTM1 genotypes was 2.51, which increased with the smoking habit (OR = 2.98). In Region II, the cancer mortality rate for As-associated cancers at least partly might be related to differences in As biotransformation. Genetic biomarkers such as 2A and GSTM1 polymorphisms in addition to DR70 as screening biomarkers might provide relevant information to identify individuals with a high risk for lung cancer as prevention and protection actions to protect public health.

PAHs and Mutagenicity of Inhalable and Respirable Diesel Particulate Matter in Santiago, Chile

Delayed human effects such as cancer could be a consequence of chronic exposure, over long periods of time, to inhalable (PM10) and respirable (PM2.5) particles containing environmental carcinogen mixtures. Air pollution in Santiago, Chile, is a major public health problem due to the high levels of regulated pollutants such as PM10, CO, and ozone. In this work, we studied the levels of polycyclic aromatic hydrocarbons (PAHs) onto PM10 and PM2.5 collected in diesel revision plants, in an urban area with a high flow of buses and trucks and in a rural area not exposed to diesel emissions. The PM10 average levels in diesel emission plants were higher than the Chilean PM10 standard and higher than those found in the urban and rural areas. In the urban area the PM10 average levels were lower than the Chilean PM10 standard, although some 24 h levels surpassed the levels established to decree preemergency or emergency and in some cases were higher than the levels reported by all the official monitoring stations. The levels of total PAHs onto PM10 were higher in the diesel plants than in the urban area and rural area, but the levels of six carcinogenic PAHs were similar in the diesel plants to those found in the urban area. Organic extracts from PM10 collected in diesel plants in Salmonella typhimurium TA98 in the presence and in the absence of an S9 activation system were significantly higher than in the urban area and rural area. Mutagenic activity with and without S9 in diesel plants and the urban area showed that indirect (PAHs) and direct (nitro-PAHs) mutagenic compounds are present in organic extracts from PM10. In conclusion, these results showed that in Santiago diesel emission particles were highly mutagenic and contain carcinogenic PAHs. This might represent a risk for long-term respiratory effects in Santiagos inhabitants.

Polycyclic Aromatic Hydrocarbon Levels and Mutagenic Activities of Organic Extracts from Airborne Particles in Santiago de Chile

The levels of 16 polycyclic aromatic hydrocarbons (PAHs) in airborne parti cles were determined by high-pressure liquid chromatography (HPLC) in 97 samples collected in downtown Santiago de Chile. The mean annual concen tration was 260 ng·m -3 (range 71.80-1,345 ng·m-3). Six PAHs classified as carcinogenic by the WHO comprised 45% of the total PAHs. The annual mean concentration for benzo(a)pyrene was 18.25 ng·m-3 (range 2.08-130.30 ng·m -3), much higher than reported levels for several European and American cities. Levels in the cold season were, on average, 2.87 times higher than in the hot season. Principal component analysis and Pearson correlation analysis were used to analyse the PAHs profiles. Organic extracts of particulate matter were examined by the Ames test using strain TA 98 ± S9 and all samples showed a very high mutagenic response both ± S9. The mutagenicity of the extracts was much higher than reported from studies in other countries. Ear lier work with the strains TA 98 NR and TA 98/1,8 DNP6 had suggested that the extracts also contained mononitro- and dinitro-arenes. Continual expo sure to particulates containing carcinogenic PAHs and nitroarenes represents a health risk for Santiago residents.

Indoor Air Pollution in a Zone of Extreme Poverty of Metropolitan Santiago, Chile

Few studies have been done on indoor air pollution in areas of extreme poverty in developing countries. In such countries, for economic reasons, people use solid fuel for cooking and heating fuels which by incomplete combustion generate high levels of toxic pollutants. These represent an important risk factor for human health. We have investigated the levels of carbon monoxide (CO), sulphur dioxide (SO2), respirable particulate matter (PM10 ), polycyclic aromatic hydrocarbons (PAHs) and mutagenicity in the PM5 fraction, as well as temperature and humidity, in the interior of 24 houses in La Pintana, Santiago. In addition, we have conducted a survey about symptoms, signs and respiratory diseases possibly associated with socio-economic factors in the area. The survey showed that in children younger than 2 years, most respiratory diseases occur during winter (75%), the most frequent complaint being bronchitis (62%) and obstructive bronchitis (50%). The higher pollutant concentrations were observed during heating hours, in houses that used coal (mean PM10 250 µg·m–3, CO 42 ppm, SO2 192 ppb) or firewood (mean PM10 489 µg·m–3, CO 57 ppm, SO2 295 ppb). PAHs were detected in all houses and we concluded that they came from inside the house and not from outdoor infiltration. Coal, firewood and cigarette smoke were important sources of mutagenic and carcinogenic PAHs, whereas kerosene and gas contributed mainly to the non-carcinogenic PAH fraction. In the houses studied, the population was exposed to levels of toxic pollutants that are much higher than those found outdoors in the highly polluted city of Santiago. In addition, overcrowding, excessive indoor humidity, very low indoor temperatures when the heating system was turned off, the presence of domestic animals, cats and dogs indoors and general lack of hygiene (with attendant bacteria and fungi) are risk factors to explain the high incidence of respiratory diseases in children.

Occupational and environmental levels of mutagenic PAHs and respirable particulate matter associated with diesel exhaust in Santiago, Chile.

Learning ObjectivesDescribe the relationship between exposure to diesel emissions and levels of inhalable particulate matter (PM10) in this study from Santiago, Chile.Discuss the mutagenic potential of PM10 and the role played by polycyclic aromatic hydrocarbons (PAHs) absorbed onto PM10.Compare urinary levels of 1-hydroxypyrine (1-OH-P) in workers exposed and those not exposed to diesel emissions, and consider the relation of 1-OH-P levels (a marker of PAH uptake) to the CYP1A1*2A and GSTMI polymorphisms. This work studied the mutagenic potential and polycyclic aromatic hydrocarbon (PAH) levels onto PM10 collected in diesel revision plants, in an urban area as well as in a rural area in Santiago, Chile. The PM10 average levels in diesel emission plants during working hours (there is no occupational PM10 Chilean standard) were significantly higher than the atmospheric Chilean PM10 standard and highly mutagenic and with high PAHs levels. Additionally, we evaluated the contribution of CYP1A1 and GSTM1 polymorphisms on 1-OH-pyrene urinary levels. The diesel-exposed workers carrying the CYP1A1*2A allele showed significantly higher 1-OH-P levels than the subjects from the rural area with the same genotype. The higher levels of 1-OH-P were found in individuals carrying the combined CYP1A1*2A and GSTM1 null genotype. This kind of information might be relevant to establish prevention, protection, and mitigation actions to protect public health.

Whole-Genome Sequencing Analysis Identifies a Distinctive Mutational Spectrum in an Arsenic-Related Lung Tumor

Introduction: Arsenic exposure is a significant cause of lung cancer in North America and worldwide. Arsenic-related tumors are structurally indistinguishable from those induced by other carcinogens. Because carcinogens, like tobacco, induce distinctive mutational signatures, we sought to characterize the mutational signature of an arsenic-related lung tumor from a never smoker with the use of whole-genome sequencing. Methods: Tumor and lung tissues were obtained from a never smoker with lung squamous cell carcinoma (LUSC), without familiar history of lung cancer and chronically exposed to high levels of arsenic-contaminated drinking water. The Illumina HiSeq-2000 platform was used to sequence each genome at approximately 30-fold haploid coverage. The mutational signature was compared with those observed in previously characterized lung tumors. Results: The arsenic-related tumor exhibited alterations common in LUSC, such as the increased number of copies at 3q26 (SOX2 locus). However, the arsenic-related genome not only harbored a lower number of point mutations, but also had a remarkably high fraction of T>G/A>C mutations and low fraction of C>A/G>T transversions, which is uncharacteristic of LUSCs. Furthermore, at the gene level, we identified a rare G>C mutation in TP53, which is uncommon in lung tumors in general (<0.2%) but has been observed in other arsenic-related malignancies. Conclusions: We generated the first whole-genome sequence of an LUSC from a never-smoker patient chronically exposed to arsenic, and identified a distinct mutational spectrum associated with arsenic exposure, providing novel evidence supporting the hypothesis that arsenic-induced lung tumors arise through molecular mechanisms that differ from those of the common lung cancer.

Influence of Atmospheric Air Pollution on Indoor Air Quality: Comparison of Chemical Pollutants and Mutagenicity Levels in Santiago (Chile):

The influence of atmospheric pollution on indoor air quality (IAQ) was studied in downtown Santiago (Chile). Carbon monoxide (CO), nicotine, the mass of respirable particulate matter below 5 μm (PM5 fraction) and total and carcinogenic polycyclic aromatic hydrocarbons (PAHs) were simultaneously monitored indoors and outdoors in restaurants, offices and oth er places. The levels of CO changed simultaneously outdoors and indoors (r = 0.89), especially during traffic rush hours, masking the contribution of other indoor sources and showing the importance of infiltration of outdoor air indoors. CO concentrations ranged from 1.0 to 73 ppm and 0.5 to 93 ppm for indoors and outdoors, respectively. The highest running 8-hour average levels measured were 16 and 18 ppm, respectively. These levels exceeded the Chilean 8-hour standard of 9 ppm to the extent of 178% indoors and by more than 200% outdoors. PM5 concentrations were high and showed no significant differences (p > 0.05) between indoors and outdoors: levels in restaurants, offices and other places were not significantly different from each other. The concentrations of total and carcinogenic PAHs were also high indoors and outdoors, outdoor levels being higher than those indoors although no significant differences (p > 0.05) in indoor levels were found between restaurants and offices and between offices and other places. Nicotine levels showed significant differences (p < 0.05) between indoor and outdoor levels. In addition, great differences (p < 0.05) in indoor levels were also found between offices and restaurants, and offices and other places. Mutagenic response in Salmonella typhimurium by organic extracts from PM 5 collected in downtown Santiago in Bandera street and in a rural area showed that the extracts from the Santiago samples are highly mutagenic. These results suggest that in downtown Santiago, infiltration might be the main source of indoor pollution. Symptoms and health effects probably related to air pollution in people working in Bandera street and in Curacavi, a rural area located 45 km from Santiago were surveyed. This showed clearly that people working in downtown Santiago have greater frequency of eye complaints, sneezing attacks, cough, throat dryness and rhinitis.