Early Biological Effects Research Articles

Association between plasma BPDE-Alb adduct concentrations and DNA damage of peripheral blood lymphocytes among coke oven workers

Objectives: Coke oven emissions COE containing polycyclic aromatic hydrocarbons PAHs can induce both benzoapyrene-r-7, t-8, t-9,c-10-tetrahydotetrol-albumin BPDE-Alb adducts and DNA damage. However, the relation between these biomarkers for early biological...

Cell markers, cytokines, and immune parameters in cement mason apprentices

Cement masons are known to have significant silica exposure, and silica exposure and silicosis are thought to increase risk of autoimmune disease. Because the mechanisms remain obscure, with inconclusive reports of systemic immune effects following silica exposure, our goal was to identify potential early markers of silica-related immunologic and respiratory effects. We conducted a cross-sectional study of cement mason apprentices and electrician (control) apprentices. Demographics, dust exposure history, symptoms, spirometry, exhaled nitric oxide, and blood (for immunoglobulins, cytokines, cell counts, and surface markers) were obtained from 11 cement mason apprentices and a comparison group of 21 electrician apprentices. Masons had significantly higher (P < 0.05) masonry dust exposure (42 versus 9 dust-hour-years), serum interleukin-1beta (IL-1beta; 12 versus 9 pg/ml), IL-2 (20 versus 8 pg/ml), IL-4 (193 versus 67 pg/ml), IL-10 (44 versus 21 pg/ml), and interferon-gamma (139 versus 65 pg/ml) compared with electricians. In contrast, masons had significantly lower percentages of CD25+ (12% versus 20%) and CD69+ (4% versus 9%) lymphocytes. Mason apprentices had higher levels of serum proinflammatory cytokines and lower percentages of CD25+ and CD69+ lymphocytes than did electrician apprentices. These preliminary findings suggest that mason apprentices may be at greater risk of a systemic proinflammatory state that is potentially linked to immune dysregulation. Although distinct limitations of this preliminary data are recognized, this is consistent with early biologic effects leading to increased incidence of autoimmune disease among silica-exposed workers. Prospective studies are needed to validate these initial findings and clarify the temporal sequence of observed relationships.

Exposure to genotoxic agents, host factors, and lifestyle influence the number of centromeric signals in micronuclei: A pooled re-analysis

We pooled data from three biomonitoring studies using the cytokinesis-block micronucleus assay in peripheral blood lymphocytes in combination with fluorescence in situ hybridization. Centromere-positive micronuclei (C + MN) were classified in two groups: those containing one centromere (C1 + MN) and those with two or more (C x + MN). The three studies evaluated untreated cancer patients, welders, and pathologists/anatomists exposed to formaldehyde. The total number of subjects included in the pooled re-analysis was 113. A higher frequency of C + MN was observed in cancer patients and exposed workers, who showed significant differences from controls in all studies. C1 + MN were particularly increased in the group of pathologists/anatomists, who showed a 3.29 times higher frequency than controls (95% CI: 2.04–5.30). A borderline increase in C x + MN was observed in welders when compared to the corresponding control group (FR: 1.31; 95% CI: 0.99–1.74). An evident effect of gender was found, with significantly increased frequencies of all endpoints measuring aneuploidy in females (C + MN, C1 + MN, and C x + MN). Alcohol consumption had a significant effect on total MN frequency and particularly on C + MN and C1 + MN. In conclusion, scoring the number of centromeric signals in the micronucleus assay provides additional information about the mechanism of action of various genotoxic agents, and the role of confounding factors may be more specifically accounted for. Indeed, C + MN could be efficiently used in biomonitoring studies as an independent biomarker of exposure and early biological effect. The use of centromeric signals allows the identification of two further endpoints, representing two alternative pathways of chromosome loss, i.e., impaired chromosome migration, leading to increased C1 + MN frequency, and centrosome amplification, possibly leading to C x + MN with two or more centromeric signals.

Assessment of potential cancer risk in children exposed to urban air pollution in Bangkok, Thailand

Urban air pollution resulting from traffic is a major problem in many cities in Asia, including Bangkok, Thailand. This pollution originates mainly from incomplete fossil fuel combustion, e.g. transportation, and the composition of which is very complex. Some of the compounds are carcinogenic in experimental animals and in man. Polycyclic aromatic hydrocarbons (PAHs) and benzene are among the major carcinogenic compounds found in urban air pollution from motor vehicle emissions. In major cities in Asia, the levels of PAHs and benzene are relatively high compared with those in Europe or in the United States and thus people are exposed to higher levels. Biomarkers of exposure and early biological effects have been used to study the potential health effects of exposure to PAHs and benzene in air pollution in school children attending schools in inner-city Bangkok compared to those attending schools in rural areas. Bangkok school children are exposed to total PAHs at levels 3.5-fold higher than those in the rural area. Urinary 1-hydroxypyrene, a metabolite of PAH, was also significantly higher, while PAH–DNA adducts in lymphocytes were five-fold higher in Bangkok school children than rural school children. Benzene exposure in Bangkok school children was approximately two-fold higher than in rural school children. This is in agreement with the levels of biomarkers of internal benzene dose, i.e. blood benzene and urinary t, t-muconic acid. The potential health risks from exposure to genotoxic substances were assessed through DNA-damage levels and DNA repair capacity. DNA strand breaks were significantly higher, whereas DNA repair capacity was significantly reduced in Bangkok children. Genetic polymorphisms have been detected in glutathione- S-transferases (GSTs) and cytochrome P450 (CYP450) enzymes involved in the metabolism of benzene and PAHs, but these polymorphisms had no significant effects on the biomarkers of PAH exposure. Our results indicate that children living in a mega city such as Bangkok may have an increased health risk of the development of certain diseases due to exposure to genotoxic substances in air pollution compared to children living in suburban/rural areas.

Exposure assessment of benzene in Thai workers, DNA-repair capacity and influence of genetic polymorphisms

Exposure to benzene can cause DNA damage and the subsequent development of cancer. In this study, study subjects were 31 laboratory workers at a petrochemical factory and 31 gasoline service attendants. Control subjects were 34 workers from a mail sorting service center. Occupational exposures to benzene were assessed using biomarkers of exposure in blood and urine. Induction of DNA-repair capacity was assessed as a biomarker of early effect. The effects of polymorphisms in a metabolizing gene ( CYP2E1), in detoxification genes ( NQO1 and GSTT1), and in a DNA-repair gene ( XRCC1, codon 399) on biomarker levels were evaluated. The mean individual benzene exposure of laboratory workers (24.40 ± 5.82 ppb) and that of gasoline service attendants (112.41 ± 13.92 ppb) were significantly higher than in controls (1.39 ± 0.17 ppb, p < 0.001). Blood benzene levels of laboratory workers (169.12 ± 30.60 ppt) and gasoline service attendants (483.46 ± 59.62 ppt) were significantly higher than those of the controls (43.30 ± 4.89 ppt, p < 0.001). Trans, trans-muconic acid levels in post-shift urine samples collected from laboratory workers (0.14 ± 0.02 mg/g creatinine) and gasoline service attendants (0.20 ± 0.02 mg/g creatinine) were significantly higher than in urine samples of controls (0.04 ± 0.01 mg/g creatinine, p < 0.001). The level of benzene exposure was correlated with blood benzene levels ( R 2 = 0.65, p < 0.01) and post-shift urinary trans, trans-muconic acid concentrations ( R 2 = 0.49, p < 0.01). As a biomarker of early effect, DNA-repair capacity was assessed by use of the cytogenetic challenge assay, i.e., chromosomal aberrations in peripheral lymphocytes were assessed after challenging blood cultures with 1 Gy gamma radiation. A significantly lower DNA-repair capacity – determined as dicentrics in laboratory workers (0.17 per metaphase cell) and in gasoline service attendants (0.19 per metaphase cell) compared with controls (0.12 per metaphase cell, p < 0.001) – was observed. The frequency of deletions in laboratory workers (0.22 per metaphase cell) and gasoline service attendants (0.39 per metaphase cell) were significantly higher than in control workers (0.16 per metaphase cell, p < 0.01 and p < 0.001, respectively). An increase in radiation-induced dicentrics and deletions indicate a lower DNA-repair capacity in benzene-exposed workers. The influence of genetic polymorphisms on the biomarkers was assessed. Benzene-exposed workers who carried CYP2E1*1/*5 or *5/*5 genotypes excreted slightly higher levels of trans, trans-muconic acid than workers who carried the CYP2E1*1/*1 genotype. In this study, NQO1 and GSTT1 genotypes did not have any effect on the levels of trans, trans-muconic acid. In the case of XRCC1, laboratory workers with 399Arg/Gln or Gln/Gln had a lower DNA-repair capacity – measured as radiation-induced frequency of dicentrics and deletions – than those with the 399Arg/Arg genotype ( p < 0.01). Our results show that biomarkers of internal dose and early biological effect in people occupationally exposed to benzene are influenced by genetic polymorphisms in susceptibility genes.

Carboxyhemoglobin and thiocyanate as biomarkers of exposure to carbon monoxide and hydrogen cyanide in tobacco smoke

The determination of biomarkers in human body fluids is a useful tool, which allows the quantitative assessment of the exposure to chemicals or complex mixtures of chemicals and of early biological effects as a result of the exposure. Biomarkers require validation before their successful application in human studies. This review describes some general purposes of human biomonitoring and biomarkers including the requirements for validation. Risk assessment and harm reduction of smoking and tobacco products, respectively, is a very suitable field for the application of biomarkers. A brief historical review shows that the application of biomarkers of exposure and effect in human smoking goes back more than 150 years. Two ‘classical’ biomarkers of exposure to tobacco, namely carboxyhemoglobin (COHb and its equivalent carbon monoxide in exhalate, COex) and thiocyanate (SCN) in body fluids are discussed in terms of sources of exposure, metabolism, disposition kinetics and influencing host factors. Data on COHb/COex and SCN in nonsmokers and smokers as well as the power to discriminate between smokers and nonsmokers are presented. Both biomarkers are significantly correlated with the daily cigarette consumption. Smoking machine-derived yields of the precursors carbon monoxide and hydrogen cyanide were not correlated with COHb/COex and SCN, respectively. It is concluded that, while COHb/COex is a useful biomarker for assessing the smoke inhalation, preferably in controlled studies, the application of SCN in body fluids as a biomarker for smoking is limited, mainly due to the abundance of other sources for SCN.

Environmental Impacts on Children's Health in Southeast Asia

Air pollution is a serious problem in many countries in Southeast Asia, particularly in major metropolises with high levels of traffic congestion generating significant amounts of genotoxic substances. The contribution of such environmental exposure to children's illnesses, such as respiratory diseases and cancer, is a public health concern. Inner-city children may have higher levels of exposure to genotoxic substances in the air than those living in rural areas. This study was conducted in Bangkok, where ambient levels of polycyclic aromatic hydrocarbons (PAHs) and benzene are relatively high. Bangkok school children were exposed to total PAHs at about sixfold higher levels than those in rural areas, with levels of urinary 1-hydroxypyrene (1-OHP) also being significantly higher. PAH-DNA adduct levels in lymphocytes were fivefold higher in Bangkok children. Benzene exposure in Bangkok school children was more than twofold higher than the levels measured in children from the rural areas. This is in agreement with the biomarkers of internal dose, that is, blood benzene and urinary trans, trans-muconic acid (t,t-MA) levels. The potential health risks from exposure to PAHs and benzene were assessed through the use of DNA damage and DNA repair capacity as markers of early biological effect. DNA strand breaks were significantly higher in Bangkok school children, while DNA repair capacity was significantly lower. It appears that children in major cities in developing countries may have an increased health risk for the development of certain diseases, such as cancer due to exposure to genotoxic substances in their environment.

Cytogenetic effects in children and mothers exposed to air pollution assessed by the frequency of micronuclei and fluorescence in situ hybridization (FISH): A family pilot study in the Czech Republic

A family pilot study was conducted in the Czech Republic to test the hypothesis that exposure to air pollution with particulate matter (PM) in children results in detectable effects indicated by a number of biomarkers of exposure and early effects. The frequency of micronuclei (MN) in peripheral blood lymphocytes (PBLs) was analysed to assess the cytogenetic effects in children and mothers living in two different areas. From each area two groups of children from a total of 24 families (mean age: 6.0 ± 0.6 and 9.0 ± 1.2 years) in a total of 47 children and 19 mothers (mean age: 33.6 ± 3.9 years) participated. Chromosome aberrations determined with fluorescence in situ hybridization (FISH) painting for chromosomes #1 and #4 were analysed in 39 children and 20 parents. Teplice, a mining district, in Northern Bohemia was selected for the analyses of the effects in a population exposed to high levels of air pollution, especially during winter, and compared with a population from the rural area of Prachatice in Southern Bohemia. Significant higher frequencies of MN were found in the younger children living in the Teplice area as compared with those living in the Prachatice area (7.0 ± 2.3‰ versus 4.9 ± 2.0‰, p = 0.04). Higher levels of MN were also measured in the older children and the mothers from the Teplice area (9.2 ± 3.7‰ versus 6.6 ± 4.4‰) and (12.6 ± 3.4‰ versus 10.1 ± 4.0‰). The increased MN frequency may be associated with elevated carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) concentration of the PM 2.5 measured in the ambient Teplice air, but other factors like genotoxic compounds from the diet or protective effect of micronutrients, which was not addressed in this pilot study, may also differ between the two areas. MN frequencies were found to increase with age in children. Lower MN frequency was found in boys as compared to girls. The result of the FISH analyses showed a low number of individuals with detectable levels of aberrations and no significant increases in genomic frequency of stable chromosome exchanges ( F G/100) were found in children or parents from the Teplice area in comparison with those from the Prachatice area. The family pilot study indicates that MN is a valuable and sensitive biomarker for early biological effect in children and adults living in two different areas characterised with significant exposure differences in c-PAHs concentrations during winter.

Different pathways of centromeric micronuclei formation in peripheral blood lymphocytes of cancer patients and workers occupationally exposed to mutagens/carcinogens?

We pooled data from three biomonitoring studies using the cytokinesis-block micronucleus assay in peripheral blood lymphocytes in combination with fluorescence in situ hybridization. Centromere-positive micronuclei (C + MN) were classified in two groups: those containing one centromere (C1 + MN) and those with two or more (Cx + MN). The three studies evaluated untreated cancer patients, welders, and pathologists/anatomists exposed to formaldehyde. The total number of subjects included in the pooled re-analysis was 113. A higher frequency of C + MN was observed in cancer patients and exposed workers, who showed significant differences from controls in all studies. C1 + MN were particularly increased in the group of pathologists/anatomists, who showed a 3.29 times higher frequency than controls (95% CI: 2.04–5.30). A borderline increase in Cx + MN was observed in welders when compared to the corresponding control group (FR: 1.31; 95% CI: 0.99–1.74). An evident effect of gender was found, with significantly increased frequencies of all endpoints measuring aneuploidy in females (C + MN, C1 + MN, and Cx + MN). Alcohol consumption had a significant effect on total MN frequency and particularly on C + MN and C1 + MN. In conclusion, scoring the number of centromeric signals in the micronucleus assay provides additional information about the mechanism of action of various genotoxic agents, and the role of confounding factors may be more specifically accounted for. Indeed, C + MN could be efficiently used in biomonitoring studies as an independent biomarker of exposure and early biological effect. The use of centromeric signals allows the identification of two further endpoints, representing two alternative pathways of chromosome loss, i.e., impaired chromosome migration, leading to increased C1 + MN frequency, and centrosome amplification, possibly leading to Cx + MN with two or more centromeric signals.

Decreased levels of CXC-chemokines in serum of benzene-exposed workers identified by array-based proteomics

Benzene is an important industrial chemical and environmental contaminant that causes leukemia. To obtain mechanistic insight into benzene's mechanism of action, we examined the impact of benzene on the human serum proteome in a study of exposed healthy shoe-factory workers and unexposed controls. Two sequential studies were performed, each using sera from 10 workers exposed to benzene (overall mean benzene air level >30 ppm) and 10 controls. Serum samples were subjected to anion-exchange fractionation and bound to three types of ProteinChip arrays (Ciphergen Biosystems, Fremont, CA) [hydrophobic (H50), metal affinity (IMAC3-Cu), and cation exchange (WCX2)]. Protein-expression patterns were detected by surface-enhanced laser desorption/ionization (SELDI)-TOF MS. Three proteins (4.1, 7.7, and 9.3 kDa) were consistently down-regulated in exposed compared with control subjects in both studies. All proteins were highly inversely correlated with individual estimates of benzene exposure (r > 0.75). The 7.7- and 9.3-kDa proteins were subsequently identified as platelet factor (PF)4 and connective tissue activating peptide (CTAP)-III. Initial proteomic results for PF4 and CTAP-III were subsequently confirmed in a single experiment using a ProteinChip-array-based immunoassay(Ciphergen Biosystems). The altered expression of the platelet-derived CXC-chemokines (40% and 63% for PF4 and CTAP-III, respectively) could not be explained by changes in absolute platelet counts. Thus, SELDI-TOF analysis of a limited number of exposed and unexposed subjects revealed that lowered expression of PF4 and CTAP-III proteins is a potential biomarker of benzene's early biologic effects and may play a role in the immunosuppressive effects of benzene.

Nonclassical Action of Retinoic Acid on the Activation of the cAMP Response Element-binding Protein in Normal Human Bronchial Epithelial Cells

Vitamin A (retinol) is essential for normal regulation of cell growth and differentiation. We have shown that the retinol metabolite retinoic acid (RA) induces mucous cell differentiation of normal human tracheobronchial epithelial (NHTBE) cells. However, early biological effects of RA in the differentiation of bronchial epithelia are largely unknown. Here, we showed that RA rapidly activated cAMP response element-binding protein (CREB). However, RA did not use the conventional retinoic acid receptor (RAR)/retinoid X receptor (RXR) to activate CREB. RA activated CREB in NHTBE and H1734 cells in which RARs/RXR were silenced with small interfering RNA (siRNA) targeting RAR/RXR expression or deactivated by antagonist. Inhibition of protein kinase C (PKC) or extracellular regulated kinase (ERK1/2) blocked the RA-mediated activation of CREB. In addition, depletion of p90 ribosomal S6 kinase (RSK) via siRSK1/2 completely abolished the activation, suggesting that PKC, ERK, and RSK are required for the activation. Altogether, this study provides the first evidence that RA rapidly activates CREB transcription factor via PKC, ERK, and RSK in a retinoid receptor-independent manner in normal bronchial epithelial cells. This noncanonical RA signaling pathway may play an important role in mediating early biological effects in the mucociliary differentiation of bronchial epithelia.

Possible genetic damage in the Czech nuclear power plant workers

The aim of our study was to identify occupational risk of irradiation exposure in the Czech nuclear power plant workers. We analyzed levels of chromosomal aberrations, a well-known biomarker of early biological effects and a predictor of cancer risk. We applied the conventional method of cytogenetic analysis and fluorescence in situ hybridization (FISH, whole chromosome painting for chromosomes 1 and 4, combined with a pancentromeric probe) to three groups: 123 subjects in the Temelin nuclear power plant (2 years in use), 114 subjects in the Dukovany nuclear power plant (20 years in use), and 53 matched controls from Ceske Budejovice. Nuclear power plant workers were divided into two groups: subjects with admittance into the monitored zone, and others. Following factors were also analyzed: GSTM1, GSTT1, GSTP1, XPD, XRCC1, hOGG1, p53, MTHFR, and MS gene polymorphisms, levels of vitamins A, C, E, and folate in plasma, and level of cotinine in urine. Long-term exposure to ionizing radiation in the monitored zone was 0.47 ± 1.50 mSv (miliSievert) in the Temelin nuclear power plant and 5.74 ± 9.57 mSv in the Dukovany nuclear power plant. Using the conventional cytogenetic analysis, we observed 1.90 ± 0.95 and 1.82 ± 1.19% AB.C. (percent of aberrant cells) in the Temelin nuclear power plant, and 2.39 ± 1.01 and 2.33 ± 1.04% AB.C. in the Dukovany nuclear power plant, for monitored zone workers and others, respectively. In the control group, we found 2.25 ± 0.82% AB.C. Genomic frequency of translocations F G/100 measured by FISH was 1.89 ± 1.40 and 2.01 ± 1.68 in the Temelin nuclear power plant, and 2.48 ± 1.93 and 2.14 ± 1.62 in the Dukovany nuclear power plant for monitored zone workers and others, respectively. In the control group, F G/100 was 1.83 ± 1.19. Following factors were identified as potential confounders by the conventional cytogenetic analysis: XPD-6, by the FISH: age, GSTP1 and p53Bst genotypes, long-term use of medication, alcohol consumption, and smoking. No association between the dose of irradiation and the level of chromosomal aberrations in any nuclear power plant was detected either by the conventional cytogenetic analysis or by FISH.

Health status of Mya arenaria bivalves collected from contaminated sites in Canada (Saguenay Fjord) and Denmark (Odense Fjord) during their reproductive period

The purpose of this study was to examine the health status and gametogenetic activity in Mya arenaria clams collected at various sites in the St. Lawrence Estuary (Quebec, Canada) and in the Odense Fjord (Denmark). Clam soft tissues were analyzed for metals/metalloids and organotin compounds to confirm their exposure to these contaminants. Their health status was assessed by a test battery of biomarkers designed to measure the early biological effects of contaminants, which include expression of defence mechanisms such as xenobiotic conjugation (glutathione S-transferase), expression of stress proteins (i.e., heme oxygenase and metallothioneins), changes in gametogenetic activity, and individual morphometric characteristics. Clam tissues were also examined for the presence of oxidative damage to lipids, formation of DNA strand breaks, and alterations in heme metabolism. The results showed that clams sampled from sites with either ferry activity or intensive boat traffic in marinas were contaminated by metals/metalloids such as Ag, Al, As, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sn, V, and Zn. The clams also contained relatively high amounts of tributyltin (TBT) in their tissues (in the ng TBT/g range for both areas), with digestive glands containing more organotins than did gonadal tissues. Moreover, clams collected from TBT-contaminated sites had higher amounts of tin–heme adducts and lower total heme in their digestive glands. Condition factor, age distribution, and sex ratio were significantly altered in clams from impacted sites in the Saguenay Fjord and accompanied by an increased male/female sex ratio. Gametogenetic activity was also negatively affected, as revealed by reductions in gonadosomatic index, maturation index, aspartate transcarbamylase activity, and vitellogenin-like proteins. The Saguenay Fjord clams displayed a complex pattern of stress responses and damage such as increased heme oxygenase activity, phase 2 conjugation enzyme activity, lipid peroxidation, and altered DNA strand breaks. The integration of biomarker response data into a biomarker index at the whole-individual level (morphometric characteristics) and for various organs (gill, digestive gland, and gonad) revealed that, relative to the control site, morphological characteristics and gonadal activity were most affected at the most contaminated site, while the effects were more pronounced in the digestive gland and gill at moderately impacted sites. We conclude that the health status of M. arenaria clams at these contaminated sites is compromised, with obvious disruption of reproductive activity.

Aging and the environment: a research framework.

The rapid growth in the number of older Americans has many implications for public health, including the need to better understand the risks posed to older adults by environmental exposures. Biologic capacity declines with normal aging; this may be exacerbated in individuals with pre-existing health conditions. This decline can result in compromised pharmacokinetic and pharmacodynamic responses to environmental exposures encountered in daily activities. In recognition of this issue, the U.S. Environmental Protection Agency (EPA) is developing a research agenda on the environment and older adults. The U.S. EPA proposes to apply an environmental public health paradigm to better understand the relationships between external pollution sources → human exposures → internal dose → early biologic effect → adverse health effects for older adults. The initial challenge will be using information about aging-related changes in exposure, pharmacokinetic, and pharmacodynamic factors to identify susceptible subgroups within the diverse population of older adults. These changes may interact with specific diseases of aging or medications used to treat these conditions. Constructs such as “frailty” may help to capture some of the diversity in the older adult population. Data are needed regarding a) behavior/activity patterns and exposure to the pollutants in the microenvironments of older adults; b) changes in absorption, distribution, metabolism, and excretion with aging; c) alterations in reserve capacity that alter the body’s ability to compensate for the effects of environmental exposures; and d) strategies for effective communication of risk and risk reduction methods to older individuals and communities. This article summarizes the U.S. EPA’s development of a framework to address and prioritize the exposure, health effects, and risk communications concerns for the U.S. EPA’s evolving research program on older adults as a susceptible subpopulation.

Differential Gene Expression in Human Peripheral Blood Mononuclear Cells Induced by Cigarette Smoke and Its Constituents

In current molecular epidemiology studies, a wide range of methods are used to monitor early biological effects after exposure to xenobiotic agents. Gene expression profiling is considered a promising tool that may provide more sensitive, mechanism-based biomarkers. As a first step toward obtaining information on the applicability of gene expression profiles as a biomarker for early biological effects of carcinogen exposure, we conducted in vitro studies on human peripheral blood mononuclear cells (PBMC). We used cigarette smoke condensate (CSC) and a selection of its genotoxic constituents as model agents, applying cDNA microarray technology to investigate modulated gene expression. In independent experiments using cells from several donors, quiescent PBMC were exposed for 18 h, followed by gene expression analyses on a microarray containing 600 toxicologically relevant genes. The search for candidate biomarker genes was binomial: first we looked for genes responding similarly to all agents; second, for agent-specific genes. Many genes were significantly deregulated by all compounds, but as the direction of deregulation frequently differed per agent, they are not useful as generic biomarkers. Cigarette smoke condensate modulated the expression of many more genes than any of its constituents, with the largest effect in SERPINB2. The affected genes are involved in immune or stress responses, but surprisingly no genes involved in DNA damage response were modulated, and only a few in DNA repair. In conclusion, several genes have been identified as potential biomarkers for population studies on early biological effects caused by cigarette smoke exposure, but no genes were identified that represent a generic biomarker.

Biomarkers of exposure, effect, and susceptibility of arsenic-induced health hazards in Taiwan

Long-term exposure to inorganic arsenic from drinking water has been documented to induce cancers and vascular diseases in a dose-response relationship. A series of molecular environmental epidemiological studies have been carried out to elucidate biomarkers of exposure, effect, and susceptibility for arsenic-related health hazards in Taiwan. Arsenic levels in urine, hair, and nail are biomarkers for short-term (<1 year) internal dose, skin hyperpigmentation and palmoplantar hyperkeratosis are for long-term (many years) internal dose, and percentage of monomethylarsonic acid in total metabolites of inorganic arsenic in urine may be considered as an exposure marker for biologically effective dose. The biomarkers of early biological effects of ingested inorganic arsenic included blood levels of reactive oxidants and anti-oxidant capacity, genetic expression of inflammatory molecules, as well as cytogenetic changes including sister chromatid exchange, micronuclei, and chromosome aberrations of peripheral lymphocytes. Both mutation type and hot spots of p53 gene were significantly different in arsenic-induced and non-arsenic-induced TCCs. The frequency of chromosomal imbalances analyzed by comparative genomic hybridization and the frequency of loss of heterozygosity were significantly higher in arsenic-induced TCC than non-arsenic-induced TCC at specific sites. Biomarkers of susceptibility to arsenic-induced health hazards included genetic polymorphisms of enzymes involved in xenobiotic metabolism, DNA repair, and oxidative stress, as well as serum level of carotenoids. Gene–gene and gene–environment interactions are involved in arsenic-induced health hazards through toxicological mechanisms including genomic instability and oxidative stress.

Spectrophotometric Determination of Plasma and Red Blood Cell Cholinesterase Activity of 53 Fruit Farm Workers Pre- and Post-Exposed Chlorpyrifos for One Fruit Crop

We sought to investigate the early biological effects of chlorpyrifos among 53 Thai fruit farm workers by measuring the plasma cholinesterase (PChE) and red blood cell cholinesterase (AChE) activities, a biomarker of organophosphate (OPs) pesticide during one fruit crop. The ChE activity (V(m)/K(m)) was spectrophotometrically analyzed before and after exposing to chlorpyrifos. The V(m)/K(m) values of both non-spraying and spraying seasons are found as normal distribution pattern. The median PChE and AChE activities among farm workers in the non-spraying season were 2.3 x 10(-3) s(-1) and 7.26 x 10(-5) s(-1), respectively. The median PChE and AChE activities of the farm workers in the spraying season were 2.02 x 10(-3) s(-1) and 5.95 x 10(-5) s(-1), respectively. The mean V(m)/K(m) values of PChE shifted left (t-test, p=0.013), indicating a decrease in PChE activity in the farm workers exposed to chlorpyrifos. However, the V(m)/K(m) values of AChE in nonspraying season and in the spraying season were not different (t-test, p=0.246). We propose that PChE activity can be used as a biomarker for monitoring early toxicity induced by chlorpyrifos insecticide.

PCB Exposure and in Vivo CYP1A2 Activity among Native Americans

Cytochrome P-450 1A2 (CYP1A2) is an enzyme involved in the metabolic activation of some carcinogens and is believed to be induced by xenobiotics. Very few studies, however, have investigated the association between environmental exposures and in vivo CYP1A2 activity in humans. To address this issue, a study was conducted of CYP1A2 activity among Native Americans exposed to polychlorinated biphenyls (PCBs) from the consumption of fish from the St. Lawrence River. At the Mohawk Nation at Akwesasne (in New York and in Ontario and Quebec, Canada), 103 adults were interviewed, and they donated blood for serum PCB analysis and underwent the caffeine breath test (CBT), a safe and noninvasive procedure that uses caffeine as a probe for CYP1A2 activity in vivo. The results supported the findings of other studies that CBT values are higher among smokers and men and lower among women who use oral contraceptives. Despite a relatively low average total PCB body burden in this population, the sum of serum levels for nine mono- or di-ortho-substituted PCB congeners showed positive associations with CBT values (p = 0.052 wet weight and p = 0.029 lipid adjusted), as did toxic equivalent quantities (TEQs; p = 0.091 for wet weight and 0.048 for lipid adjusted). Regarding individual congeners, serum levels of PCB-153, PCB-170, and PCB-180 were significantly correlated with CBT values. The results support the notion that CYP1A2 activity may be a marker of an early biological effect of exposure to PCBs in humans and that the CBT may be a useful tool to monitor such effects.

Assessing Biomarker use in Risk Assessment—A Survey of Practitioners

Advances in molecular epidemiology and mechanistic toxicology have provided increased opportunities for incorporating biomarkers in the human health risk assessment process. For years, the published literature has lauded the concept of incorporating biomarkers into risk assessments as a means to reduce uncertainty in estimating health risk. For all the potential benefits, one would think that markers of effective dose, markers of early biological effects, and markers of human susceptibility are frequently selected as the basis for quantitative human health risk assessments. For this article, we sought to determine the degree to which this evolution in risk assessment has come to pass. The extent to which biomarkers are being used in current human health risk assessment was determined through an informal survey of leading risk assessment practitioners. Case studies highlighting the evolution of risk assessment methods to include biomarkers are also described. The goal of this review was to enhance the implementation of biomarker technology in risk assessment by (1) highlighting successes in biomarker implementation, (2) identifying key barriers to overcome, and (3) describing evolutions in risk assessment methods.

Detailed exposure assessment for a molecular epidemiology study of benzene in two shoe factories in China.

We carried out a detailed exposure assessment of benzene and toluene in two shoe factories in Tianjin, China. Our goal was to identify workers with a broad range of benzene exposures, for an epidemiologic study relating exposure to early biologic effects. A comprehensive exposure survey program was initiated. Over a period of 16 months, 2783 personal solvent exposure samples were collected in two workplaces from 250 workers. Mixed-effects models were used to identify factors affecting exposure. Principal component analyses (PCA) and subsequent regression analyses on the scores of the identified principal components were used to relate potential co-exposures to various exposure sources present in the workplace. The mean benzene exposure level was 21.86 p.p.m. (10th-90th percentiles 5.23-50.63 p.p.m.) in the smaller shoe factory (factory A) and 3.46 p.p.m. (10th-90th percentiles 0.20-7.00 p.p.m.) in the larger shoe factory (factory B). Within-factory exposure levels differed among job titles and were higher for subjects directly involved in handling glues. In contrast, mean toluene levels were relatively similar in the two factories (factory A, 9.52 p.p.m.; factory B, 15.88 p.p.m.). A seasonal trend was identified for both benzene and toluene in factory B. This could be explained in part by changes in air movement and ventilation patterns occurring during the year. A seasonal trend was not present in the smaller shoe factory, where general ventilation was absent. Supplemental analysis showed that exposure levels to other hydrocarbons were low (< or =5 p.p.m.), less than 5% of their respective ACGIH threshold limit values, and generally comparable in the two factories. PCA showed that co-exposures in factory B could largely be explained by glue sources that were used in distinct areas in the workplace. We demonstrated the occurrence of a broad range of benzene exposure levels in two shoe manufacturing factories in Tianjin, China. Benzene and toluene exposures were determined in part by the degree of contact with glues, the benzene and toluene content of each glue, air movement and ventilation patterns. The availability of long-term monthly personal monitoring data provides an excellent opportunity to estimate individual exposures at different times during the 1 yr period of observation.