The light at the end of the tunnel for chemical-specific biomarkers: daylight or headlight?

Fifty Years of Aflatoxin Research in Qidong, China: A Celebration of Team Science to Improve Public Health

The Qidong Liver Cancer Institute (QDLCI) and the Qidong Cancer Registry were established in 1972 with input from doctors, other medical practitioners, and non-medical investigators arriving from urban centers such as Shanghai and Nanjing. Medical teams were established to quantify the extent of primary liver cancer in Qidong, a corn-growing peninsula on the north side of the Yangtze River. High rates of liver cancer were documented and linked to several etiologic agents, including aflatoxins. Local corn, the primary dietary staple, was found to be consistently contaminated with high levels of aflatoxins, and bioassays using this corn established its carcinogenicity in ducks and rats. Observational studies noted a positive association between levels of aflatoxin in corn and incidence of liver cancer across townships. Biomarker studies measuring aflatoxin B1 and its metabolite aflatoxin M1 in biofluids reflected the exposures. Approaches to decontamination of corn from aflatoxins were also studied. In 1993, investigators from Johns Hopkins University were invited to visit the QDLCI to discuss chemoprevention studies in some townships. A series of placebo-controlled clinical trials were conducted using oltipraz (a repurposed drug), chlorophyllin (an over-the-counter drug), and beverages prepared from 3-day-old broccoli sprouts (rich in the precursor phytochemical for sulforaphane). Modulation of biomarkers of aflatoxin DNA and albumin adducts established proof of principle for the efficacy of these agents in enhancing aflatoxin detoxication. Serendipitously, by 2012, aflatoxin exposures quantified using biomarker measurements documented a many hundred-fold reduction. In turn, the Cancer Registry documents that the age-standardized incidence rate of liver cancer is now 75% lower than that seen in the 1970s. This reduction is seen in Qidongese who have never received the hepatitis B vaccination. Aflatoxin mitigation driven by economic changes switched the dietary staple of contaminated corn to rice coupled with subsequent dietary diversity leading to lower aflatoxin exposures. This 50-year effort to understand the etiology of liver cancer in Qidong provides the strongest evidence for aflatoxin mitigation as a public health strategy for reducing liver cancer burden in exposed, high-risk populations. Also highlighted are the challenges and successes of international team science to solve pressing public health issues.

65 Years on-Aflatoxin Biomarkers Blossoming: Whither Next?

Aflatoxins are mycotoxins produced by Aspergillus flavus and several other related organisms and are common contaminants of numerous grains and nuts, especially maize (corn) and peanuts. Although, undoubtedly, aflatoxins have been present in the food of humans for millennia, their toxic effects were not discovered until 1960, first becoming evident as a non-infectious outbreak of poisoning of turkeys (Turkey X disease) arising from contaminated groundnut meal. The elucidation of specific chemical structures in 1963 led to the rapid characterization of aflatoxins as among the most potent chemical carcinogens of natural origin ever discovered. As a frontispiece to the Special Issue "65 Years on from Aflatoxin Discovery-A Themed Issue in Honor of Professor John D. Groopman", we highlight many of Professor Groopman's important contributions utilizing urinary (aflatoxin-N7-guanine) and, especially, serum (aflatoxin-albumin adducts) biomarkers; this work focused on over 40+ years of the development of analytical methods to measure biomarkers of aflatoxin exposure and their application in experimental and clinical studies. Collectively, this work serves as a template for using chemical-specific biomarkers as key tools to probe 'exposure-disease relationships'-in this instance, dietary aflatoxins and liver cancer. New approaches to measuring carcinogen biomarkers will build upon this 'aflatoxin paradigm' to inform the public health implications of diverse exposures around the world.

Development of a protocol of isolation of nanoparticles from patients' broncho-alveolar lavages for their in vitro toxicity assessment

To investigate potential correlations between human exposure to inhaled particles and pathological effects, the biological monitoring of nanoparticles in broncho-alveolar lavages (BAL) from patients has been proposed. To better understand the underlying mechanisms of toxicity, we propose to couple this biomonitoring of nanoparticles to their in vitro toxicity assessment. However, BAL obtained from regular clinical practice are conditioned with sodium hypochlorite solution (in a 50% v/v ratio), which is toxic to cells. The aim of this study was to develop a protocol to neutralize sodium hypochlorite, allowing to properly investigate the toxicity of the nanoparticles BAL contain. We first tried to neutralize chemically the sodium hypochlorite using H2O2, ascorbic acid or sodium ascorbate but this approach was unsuccessful. In addition, standard toxicology assays (MTT, LDH) could not be used because of interference with neutralizing solutions. We thus changed strategy and used ultracentrifugation to isolate nanoparticles from the sodium hypochlorite solution, with satisfactory extraction yields (88 to 100%). We then incubated the extracted nanoparticles with macrophages from the RAW264.7 cell line and assessed the cell viability and pro-inflammatory response. This study can be used as a proof-of-concept for further study of the biological impact of nanoparticles. This approach paves the way for studies aiming at a better understanding of the aetiology of some idiopathic diseases and underlying mechanisms.

PINK1/Parkin-mediated mitophagy is activated to protect against AFB1-induced immunosuppression in mice spleen

Aflatoxin B₁ (AFB₁) can cause mitochondrial malfunction and immunosuppression in spleen. Mitochondrial damage can lead to oxidative stress and aggravate immune cell dysfunction. Phosphatase and tensin homolog (PTEN)-induced putative kinase1 (PINK1)/ E3 ubiquitin ligase PARK2 (Parkin)-mediated mitophagy can scavenge damaged mitochondria and alleviate oxidative stress to maintain cellular homeostasis. However, the role of PINK1/Parkin-mediated mitophagy in AFB₁-induced immunosuppression in spleen is unclear. In this study, sixty male mice were sensibilized orally with AFB₁ at different concentrations [0, 0.5, 0.75, and 1 mg/kg body weight (BW)] for 28 days, and AFB₁ caused splenic structure injury and immunosuppression, also led to upregulation of PINK1/Parkin-mediated mitophagy in a dose-dependent manner. Subsequently, thirty male WT C57BL/6 N mice and thirty male Parkin knockout (Parkin^-/-) C57BL/6 N mice were sensibilized orally with AFB₁ at 0 or 1 mg/kg BW for 28 days, and Parkin^-/- inhibited mitophagy and further aggravated AFB₁-induced splenic structure injury, immunosuppression, mitochondrial damage and oxidative stress. Collectively, these results indicate that AFB₁ exposure activates PINK1/Parkin-mediated mitophagy, which protects against immunosuppression in spleen.

Experimental and Computational Nanotoxicology-Complementary Approaches for Nanomaterial Hazard Assessment

The growing development and applications of nanomaterials lead to an increasing release of these materials in the environment. The adverse effects they may elicit on ecosystems or human health are not always fully characterized. Such potential toxicity must be carefully assessed with the underlying mechanisms elucidated. To that purpose, different approaches can be used. First, experimental toxicology consisting of conducting in vitro or in vivo experiments (including clinical studies) can be used to evaluate the nanomaterial hazard. It can rely on variable models (more or less complex), allowing the investigation of different biological endpoints. The respective advantages and limitations of in vitro and in vivo models are discussed as well as some issues associated with experimental nanotoxicology. Perspectives of future developments in the field are also proposed. Second, computational nanotoxicology, i.e., in silico approaches, can be used to predict nanomaterial toxicity. In this context, we describe the general principles, advantages, and limitations especially of quantitative structure–activity relationship (QSAR) models and grouping/read-across approaches. The aim of this review is to provide an overview of these different approaches based on examples and highlight their complementarity.

Relationship between Occupational Exposure to Airborne Nanoparticles, Nanoparticle Lung Burden and Lung Diseases

The biomonitoring of nanoparticles in patients’ broncho-alveolar lavages (BAL) could allow getting insights into the role of inhaled biopersistent nanoparticles in the etiology/development of some respiratory diseases. Our objective was to investigate the relationship between the biomonitoring of nanoparticles in BAL, interstitial lung diseases and occupational exposure to these particles released unintentionally. We analyzed data from a cohort of 100 patients suffering from lung diseases (NanoPI clinical trial, ClinicalTrials.gov Identifier: NCT02549248) and observed that most of the patients showed a high probability of exposure to airborne unintentionally released nanoparticles (>50%), suggesting a potential role of inhaled nanoparticles in lung physiopathology. Depending on the respiratory disease, the amount of patients likely exposed to unintentionally released nanoparticles was variable (e.g., from 88% for idiopathic pulmonary fibrosis to 54% for sarcoidosis). These findings are consistent with the previously performed mineralogical analyses of BAL samples that suggested (i) a role of titanium nanoparticles in idiopathic pulmonary fibrosis and (ii) a contribution of silica submicron particles to sarcoidosis. Further investigations are necessary to draw firm conclusions but these first results strengthen the array of presumptions on the contribution of some inhaled particles (from nano to submicron size) to some idiopathic lung diseases.

Analysis of Aflatoxin Biomarkers in the Hair of Experimental Animals

Analysis of body fluids and tissues of aflatoxin exposed individuals for the presence of aflatoxins and aflatoxin metabolites has emerged as a reliable indicator of exposure and metabolism of aflatoxins. However, current aflatoxin biomarkers are not appropriate for investigating the long-term effects of aflatoxin exposure. In this explorative study, we investigated the analysis of hair as a complementary or alternative matrix for the assessment of biomarkers of long-term aflatoxin exposure. Three groups of guinea pigs were orally dosed with 5 ugkg⁻¹bw⁻¹, 50 ugkg⁻¹bw⁻¹, and 100 ugkg⁻¹bw⁻¹ of AFB1. Urine and hair samples were collected on days 0, 1, 2, 3, 7, 30, 60, and 90 and analysed for AFB1 and AFM1 using UHPLC-MS/MS. AFB1 and AFM1 were detected in 75% and 13.6%, respectively, of the day 1 to day 7 urine samples. AFB1 was detected in hair samples collected from day 3 up to day 60. This is the first report to confirm the deposition of AFB1 in the hair of experimental animals. These findings indicate that hair analysis has the potential to provide an accurate long-term historical record of aflatoxin exposure with potentially important implications for the field of aflatoxin biomarkers.

The Health Impacts of Hazardous Chemical Exposures among Child Labourers in Low- and Middle-Income Countries

Of 218 million working children worldwide, many are suspected to be exposed to hazardous chemicals. This review aims to synthesize reported evidence over the last two decades on chemical exposure and adverse health consequences in children labourers in low- and middle-income Countries (LMIC). Included studies investigated health outcomes related to chemical exposures among child labourers aged 5-18 in LMIC. Twenty-three papers were selected for review, focusing on pesticides (n = 5), solvents (n = 3), metals (n = 13) and persistent organic pollutants (POPs) (n = 2). Adverse health effects identified among child labourers included abnormal biomarkers, for example elevated blood and urine chemical concentrations, neurobehavioural deficits and neurological symptoms, mental health issues, oxidative stress and DNA damage, poor growth, asthma, and hypothyroidism. Workplace exposure to chemicals has pernicious health effects on child labourers. Large research gaps exist, in particular for long-term health impacts through chronic conditions and diseases with long latencies. A sizeable disease burden in later life is likely to be directly attributable to chemicals exposures. We urge national and international agencies concerned with child labour and occupational health, to prioritize research and interventions aiming to reduce noxious chemical exposures in workplaces where children are likely to be present.

Predicting the Acute Liver Toxicity of Aflatoxin B1 in Rats and Humans by an In Vitro-In Silico Testing Strategy

SCOPE

High-level exposure to aflatoxin B1 (AFB1) is known to cause acute liver damage and fatality in animals and humans. The intakes actually causing this acute toxicity have so far been estimated based on AFB1 levels in contaminated foods or biomarkers in serum. The aim of the present study is to predict the doses causing acute liver toxicity of AFB1 in rats and humans by an in vitro-in silico testing strategy.

METHODS AND RESULTS

Physiologically based kinetic (PBK) models for AFB1 in rats and humans are developed. The models are used to translate in vitro concentration-response curves for cytotoxicity in primary rat and human hepatocytes to in vivo dose-response curves using reverse dosimetry. From these data, the dose levels at which toxicity would be expected are obtained and compared to toxic dose levels from available rat and human case studies on AFB1 toxicity. The results show that the in vitro-in silico testing strategy can predict dose levels causing acute toxicity of AFB1 in rats and human.

CONCLUSIONS

Quantitative in vitro in vivo extrapolation (QIVIVE) using PBK modeling-based reverse dosimetry can predict AFB1 doses that cause acute liver toxicity in rats and human.

Retrospective and Prospective Look at Aflatoxin Research and Development from a Practical Standpoint

Among the array of structurally and toxicologically diverse mycotoxins, aflatoxins have attracted the most interest of scientific research due to their high toxicity and incidence in foods and feeds. Despite the undeniable progress made in various aspects related to aflatoxins, the ultimate goal consisting of reducing the associated public health risks worldwide is far from being reached due to multiplicity of social, political, economic, geographic, climatic, and development factors. However, a reasonable degree of health protection is attained in industrialized countries owing to their scientific, administrative, and financial capacities allowing them to use high-tech agricultural management systems. Less fortunate situations exist in equatorial and sub-equatorial developing countries mainly practicing traditional agriculture managed by smallholders for subsistence, and where the climate is suitable for mould growth and aflatoxin production. This situation worsens due to climatic change producing conditions increasingly suitable for aflatoxigenic mould growth and toxin production. Accordingly, it is difficult to harmonize the regulatory standards of aflatoxins worldwide, which prevents agri-foods of developing countries from accessing the markets of industrialized countries. To tackle the multi-faceted aflatoxin problem, actions should be taken collectively by the international community involving scientific research, technological and social development, environment protection, awareness promotion, etc. International cooperation should foster technology transfer and exchange of pertinent technical information. This review presents the main historical discoveries leading to our present knowledge on aflatoxins and the challenges that should be addressed presently and in the future at various levels to ensure higher health protection for everybody. In short, it aims to elucidate where we come from and where we should go in terms of aflatoxin research/development.

Assessment of mycotoxin exposure and risk characterization using occurrence data in foods and urinary biomarkers in Brazil

This study aimed to assess the exposure of Brazilian residents (N = 86) from rural areas to multiple mycotoxins and characterize the associated risk in two sampling periods (SP) (April-May and December/2016). Mycotoxins in food and urine samples were determined by liquid chromatography coupled to tandem mass spectrometry. Mean probable daily intake (PDI) values based on occurrence data in foods in both SP varied from 0.007 to 0.013, 0.069 to 1.002, 0.119 to 0.321 and 0.013-0.156 μg kg^-1 body weight (bw) day^-1 for aflatoxins (AFs), deoxynivalenol (DON), fumonisins (FBs) and zearalenone (ZEN), respectively. Mean PDI values based on urinary biomarkers were 0.001, 84.914, 0.031, 0.377 and 0.002 μg kg^-1 bw day^-1 for AFB₁, DON, ochratoxin A (OTA), FB₁ and ZEN, respectively. Hazard quotient (HQ) calculated using food data revealed a potential health concern for ZEN in 2nd SP. HQ > 1 based on urinary biomarkers were observed for DON in the two SP. Although OTA was not detected in any food sample, the HQ based on urinary OTA levels was >1 in the 1st SP. Margin of exposure values for AF from food and urine data in the 1st SP were below 10,000, indicating potential health risks.

Quantitative relationships between lacZ mutant frequency and DNA adduct frequency in Muta™Mouse tissues and cultured cells exposed to 3-nitrobenzanthrone

The frequency of stable DNA adducts in a target tissue can be used to assess biologically effective dose; however, the utility of the metric in a risk assessment context depends on the likelihood that the DNA damage will be manifested as mutation. Previously, we employed the Muta™Mouse system to examine the induction of lacZ mutants and DNA adducts following exposure to the well-studied mutagenic carcinogen 3-nitrobenzanthrone (3-NBA). In this follow-up work, we examined the empirical relationships between total adduct frequency and mutant frequency (MF) in tissues and cultured cells following acute 3-NBA exposure. The results show a significant induction of DNA damage and lacZ mutants in liver, colon and bone marrow, as well as FE1 pulmonary epithelial cells. In contrast, lung and small intestine samples had low, but significantly elevated adduct levels, with no significant increases in lacZ MF. Additional analyses showed a significant relationship between the mutagenic efficiency of total adducts, measured as the slope of the relationships between MF and total adduct frequency, and tissue-specific mitotic index (MI). The lack of mutation response in lung, in contrast to the high in vitro MF in FE-1 lung cells, is likely related to the 100-fold difference in MI. The lack of small intestine mutagenic response may be related to limited metabolic capacity, differences in DNA repair, and /or chemically induced apoptosis that has been observed for other potent mutagens. The results indicate that interpretation of adduct frequency values in a risk assessment context can be improved by considering the MI of the target tissue; however, more generalised interpretation is hampered by tissue-specific variations in metabolic capacity and damage processing. The work provides a proof of principle regarding the use of the Muta™Mouse system to critically examine the health risks associated with tissue-specific adduct loads.

Linking DNA adduct formation and human cancer risk in chemical carcinogenesis

Over two centuries ago, Sir Percival Pott, a London surgeon, published a pioneering treatise showing that soot exposure was the cause of high incidences of scrotal cancers occurring in young men who worked as chimney sweeps. Practicing at a time when cellular pathology was not yet recognized, Sir Percival nonetheless observed that the high incidence and short latency of the chimney sweep cancers, was fundamentally different from the rare scrotal cancers typically found in elderly men. Furthermore, his diagnosis that the etiology of these cancers was related to chimney soot exposure, was absolutely accurate, conceptually novel, and initiated the field of "occupational cancer epidemiology." After many intervening years of research focused on mechanisms of chemical carcinogenesis, briefly described here, it is clear that DNA damage, or DNA adduct formation, is "necessary but not sufficient" for tumor induction, and that many additional factors contribute to carcinogenesis. This review includes a synopsis of carcinogen-induced DNA adduct formation in experimental models and in the human population, with particular attention paid to molecular dosimetry and molecular cancer epidemiology. Environ. Mol. Mutagen. 57:499-507, 2016. © 2016 Wiley Periodicals, Inc.

The effects of season and gender on the serum aflatoxins and ochratoxin A levels of healthy adult subjects from the Central Anatolia Region, Turkey

PURPOSE

This study was undertaken to determine the effects of season and gender on serum aflatoxin (AF) levels (AFG1, AFB1, AFG2 and AFB2) and ochratoxin A (OTA) concentrations of healthy adult population living in Central Anatolia Region of Turkey.

METHODS

AF levels were measured by high-performance liquid chromatography (HPLC) and OTA levels were measured by enzyme-linked immunosorbent assay (ELISA) in serum samples of healthy adults (n = 233).

RESULTS

In summer and winter, total AF levels in females were 0.98 ± 0.10 and 0.94 ± 0.12 ng/ml and in males 1.35 ± 0.17 and 0.93 ± 0.11 ng/ml, respectively. Male subjects had significantly higher serum total AF levels in summer compared with females (~38%). There was no marked seasonal change in AFG1, AFB1 and AFG2 concentrations in the whole population, except AFB2. Both of the genders had significantly higher OTA levels in winter compared with summer (~60%).

CONCLUSIONS

Overall results suggest that Central Anatolia residents are continuously exposed to AFs and OTA. Besides, season and gender can be effective in mycotoxin exposure.

Effects of dietary selenium on histopathological changes and T cells of spleen in broilers exposed to aflatoxin B1

Aflatoxin B1 (AFB1), which causes hepatocellular carcinoma and immune-suppression, is commonly found in feedstuffs. To evaluate the ability of selenium (Se) to counteract the deleterious effects of AFB1, two hundred 1-day-old male avian broilers, divided into five groups, were fed with basal diet (control group), 0.3 mg/kg AFB1 (AFB1 group), 0.3 mg/kg AFB1+0.2 mg/kg Se (+Se group I), 0.3 mg/kg AFB1+0.4 mg/kg Se (+Se group II) and 0.3 mg/kg AFB1+0.6 mg/kg Se (+Se group III), respectively. Compared with control group, the relative weight of spleen in the AFB1 group was decreased at 21 days of age. The relative weight of spleen in the three +Se groups was higher than that in the AFB1 group. By pathological observation, the major spleen lesions included congestion in red pulp and vacuoles appeared in the lymphatic nodules and periarterial lymphatic sheath in the AFB1 group. In +Se groups II and III, the incidence of major splenic lesions was decreased. The percentages of CD3+, CD3+CD4+ and CD3+CD8+ T cells in the AFB1 group were lower than those in control group from 7 to 21 days of age, while there was a marked increase in the three +Se groups compared to the AFB1 group. The results indicated that sodium selenite could improve the cellular immune function impaired by AFB1 through increasing the relative weight of spleen and percentages of splenic T cell subsets, and alleviating histopathological spleen damage.

A review on aflatoxin contamination and its implications in the developing world: a sub-Saharan African perspective

Mycotoxins contamination in some agricultural food commodities seriously impact human and animal health and reduce the commercial value of crops. Mycotoxins are toxic secondary metabolites produced by fungi that contaminate agricultural commodities pre- or postharvest. Africa is one of the continents where environmental, agricultural and storage conditions of food commodities are conducive of Aspergillus fungi infection and aflatoxin biosynthesis. This paper reviews the commodity-wise aetiology and contamination process of aflatoxins and evaluates the potential risk of exposure from common African foods. Possible ways of reducing risk for fungal infection and aflatoxin development that are relevant to the African context. The presented database would be useful as benchmark information for development and prioritization of future research. There is need for more investigations on food quality and safety by making available advanced advanced equipments and analytical methods as well as surveillance and awareness creation in the region.

Development and validation of a rapid multi-biomarker liquid chromatography/tandem mass spectrometry method to assess human exposure to mycotoxins

RATIONALE

Mycotoxins regularly occur in food worldwide and pose serious health risks to consumers. Since individuals can be exposed to a variety of these toxic secondary metabolites of fungi at the same time, there is a demand for proper analytical methods to assess human exposure by suitable biomarkers.

METHODS

This study reports on the development of a liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method for the quantitative measurement of 15 mycotoxins and key metabolites in human urine using polarity switching. Deoxynivalenol (DON), DON-3-O-glucuronide, DON-15-O-glucuronide (D15GlcA), de-epoxy DON, nivalenol (NIV), T-2 toxin, HT-2 toxin, zearalenone, zearalenone-14-O-glucuronide, α- and β-zearalenol, fumonisins B(1) and B(2) (FB(1), FB(2)), ochratoxin A (OTA) and aflatoxin M(1) (AFM(1)) were determined without the need for any cleanup using a rapid and simple dilute and shoot approach.

RESULTS

Validation was performed in the range of 0.005-40 µg L(-1) depending on the analyte and expected urinary concentration levels. Apparent recoveries between 78 and 119% and interday precisions of 2-17% relative standard deviation (RSD) were achieved. The applicability of the method was demonstrated by the analysis of urine samples obtained from Cameroon. In naturally contaminated urine samples up to six biomarkers of exposure (AFM(1), DON, D15GlcA, NIV, FB(1), and OTA) were detected simultaneously.

CONCLUSIONS

We conclude that the developed LC/MS/MS method is well suited to quantify multiple mycotoxin biomarkers in human urine down to the sub-ppb range within 18 min and without any prior cleanup. The co-occurrence of several mycotoxins in the investigated samples clearly emphasizes the great potential and importance of this method to assess exposure of humans and animals to naturally occurring mycotoxins.

In vitro studies on chemoprotective effect of borax against aflatoxin B1-induced genetic damage in human lymphocytes

A common dietary contaminant, aflatoxin B1 (AFB1), has been shown to be a potent mutagen and carcinogen in humans and many animal species. Since the eradication of AFB1 contamination in agricultural products has been rare, the use of natural or synthetic free radical scavengers could be a potential chemopreventive strategy. Boron compounds like borax (BX) and boric acid are the major components of industry and their antioxidant role has recently been reported. In the present report, we evaluated the capability of BX to inhibit the rate of micronucleus (MN) and sister chromatid exchange (SCE) formations induced by AFB1. There were significant increases (P < 0.05) in both SCE and MN frequencies of cultures treated with AFB1 (3.12 ppm) as compared to controls. However, co-application of BX (1, 2 and 5 ppm) and AFB1 resulted in decreases of SCE and MN rates as compared to the group treated with AFB1 alone. Borax gave 30-50 % protection against AFB1 induced SCEs and MNs. In conclusion, the support of borax was especially useful in aflatoxin-toxicated blood tissue. Thus, the risk on target tissues of AFB1 could be reduced and ensured early recovery from its toxicity.

Comparison of standard methods for assessing dietary intake of benzo[a]pyrene

BACKGROUND

Inconsistent presence and strength of associations between dietary benzo[a]pyrene (BaP) exposure and cancers may be due to differences in exposure assessment methods. Thus, we determined correlations of usual meat and BaP intake among three methods: food frequency questionnaires (FFQ), diet diaries, and a biomarker.

METHODS

Thirty-six nonsmokers were recruited in Baltimore, MD during 2004-2005. Meat and BaP intake estimated from baseline and follow-up FFQs combined with a BaP residue database (FFQ-RD), mean meat and BaP intake estimated from three diet diaries coupled with the residue database (Diary-RD), and mean of three urinary 1-hydroxypyrene glucuronide (1-OHPG) measurements were compared using Spearman correlations. Collections spanned approximately nine months.

RESULTS

BaP intakes from meat from the baseline [median = 6.4, interquartile range (IQR) = 13.9 ng/d] and follow-up FFQ-RD (median = 7.3, IQR = 35.7 ng/d) were higher than the Diary-RD (median = 1.1, IQR = 7.4 ng/d). Mean 1-OHPG concentration was weakly correlated with mean meat intake (r = 0.33, P = 0.05) and BaP intake from meat (r = 0.27, P = 0.11) from the Diary-RD. Mean BaP intake estimated from the Diary-RD was positively correlated with the follow-up (r = 0.35, P = 0.04) but not baseline (r = 0.20, P = 0.24) FFQ; the converse was true for meat intake.

CONCLUSIONS

Diary-RD estimates were supported by biomarker measurements, but considerable unexplained variability remained. Limited correlation among the dietary BaP exposure assessment methods could be due to differences in timeframes covered by the assessments, interpersonal variability in metabolism, deficiencies in the residue database, or nondietary exposures to BaP.

IMPACT

Limited correlation in estimated BaP intake among standard methods may contribute to inconsistent epidemiology of BaP and cancer.

Aflatoxin: a 50-year odyssey of mechanistic and translational toxicology

Since their discovery 50 years ago, the aflatoxins have become recognized as ubiquitous contaminants of the human food supply throughout the economically developing world. The adverse toxicological consequences of these compounds in populations are quite varied because of a wide range of exposures leading to acute effects, including rapid death, and chronic outcomes such as hepatocellular carcinoma. Furthermore, emerging studies describe a variety of general adverse health effects associated with aflatoxin, such as impaired growth in children. Aflatoxin exposures have also been demonstrated to multiplicatively increase the risk of liver cancer in people chronically infected with hepatitis B virus (HBV) illustrating the deleterious impact that even low toxin levels in the diet can pose for human health. The public health impact of aflatoxin exposure is pervasive. Aflatoxin biomarkers of internal and biologically effective doses have been integral to the establishment of the etiologic role of this toxin in human disease through better estimates of exposure, expanded knowledge of the mechanisms of disease pathogenesis, and as tools for implementing and evaluating preventive interventions.

Aflatoxin B1 in poultry: toxicology, metabolism and prevention

Aflatoxins (AF) are ubiquitous in corn-based animal feed and causes hepatotoxic and hepatocarcinogenic effects. The most important AF in terms of toxic potency and occurrence is aflatoxin B1 (AFB1). Poultry, especially turkeys, are extremely sensitive to the toxic and carcinogenic action of AFB1, resulting in millions of dollars in annual losses to producers due to reduced growth rate, increased susceptibility to disease, reduced egg production and other adverse effects. The extreme sensitivity of turkeys and other poultry to AFB1 is associated with efficient hepatic cytochrome P450-mediated bioactivation and deficient detoxification by glutathione S-transferases (GST). Discerning the biochemical and molecular mechanisms of this extreme sensitivity of poultry to AFB1, will contribute in the development of novel strategies to increase aflatoxin resistance. Since AFB1 is an unavoidable contaminant of corn-based poultry feed, chemoprevention strategies aimed at reducing AFB1 toxicity in poultry and in other animals have been the subject of numerous studies. This brief review summarizes many of the key recent findings regarding the action of aflatoxins in poultry.

Boric acid: a potential chemoprotective agent against aflatoxin b(1) toxicity in human blood

Aflatoxin B(1) is the most potent pulmonary and hepatic carcinogen. Since the eradication of Aflatoxin B(1) contamination in agricultural products has been difficult, the use of natural or synthetic free radical scavengers could be a potential chemopreventive strategy. Boric acid is the major component of industry and its antioxidant role has recently been reported. The present study assessed, for the first time, the effectiveness of boric acid following exposure to Aflatoxin B(1) on human whole blood cultures. The biochemical characterizations of glutathione and some enzymes have been carried out in erythrocytes. Alterations in malondialdehyde level were determined as an index of oxidative stress. The sister-chromatid exchange and micronucleus tests were performed to assess DNA damages in lymphocytes. Aflatoxin B(1) treatment significantly reduced the activities of antioxidants by increasing malondialdehyde level (30.53 and 51.43%) of blood, whereas, the boric acid led to an increased resistance of DNA to oxidative damage induced by Aflatoxin B(1) in comparison with control values (P < 0.05). In conclusion, the support of boric acid was especially useful in Aflatoxin-toxicated blood. Thus the risk on tissue targeting of Aflatoxin B(1) could be reduced ensuring early recovery from its toxicity.

Approaches to advancing quantitative human health risk assessment of environmental chemicals in the post-genomic era

The contribution of genomics and associated technologies to human health risk assessment for environmental chemicals has focused largely on elucidating mechanisms of toxicity, as discussed in other articles in this issue. However, there is interest in moving beyond hazard characterization to making more direct impacts on quantitative risk assessment (QRA)--i.e., the determination of toxicity values for setting exposure standards and cleanup values. We propose that the evolution of QRA of environmental chemicals in the post-genomic era will involve three, somewhat overlapping phases in which different types of approaches begin to mature. The initial focus (in Phase I) has been and continues to be on "augmentation" of weight of evidence--using genomic and related technologies qualitatively to increase the confidence in and scientific basis of the results of QRA. Efforts aimed towards "integration" of these data with traditional animal-based approaches, in particular quantitative predictors, or surrogates, for the in vivo toxicity data to which they have been anchored are just beginning to be explored now (in Phase II). In parallel, there is a recognized need for "expansion" of the use of established biomarkers of susceptibility or risk of human diseases and disorders for QRA, particularly for addressing the issues of cumulative assessment and population risk. Ultimately (in Phase III), substantial further advances could be realized by the development of novel molecular and pathway-based biomarkers and statistical and in silico models that build on anticipated progress in understanding the pathways of human diseases and disorders. Such efforts would facilitate a gradual "reorientation" of QRA towards approaches that more directly link environmental exposures to human outcomes.

Nrf2: friend or foe for chemoprevention?

Health reflects the ability of an organism to adapt to stress. Stresses--metabolic, proteotoxic, mitotic, oxidative and DNA-damage stresses--not only contribute to the etiology of cancer and other chronic degenerative diseases but are also hallmarks of the cancer phenotype. Activation of the Kelch-like ECH-associated protein 1 (KEAP1)-NF-E2-related factor 2 (NRF2)-signaling pathway is an adaptive response to environmental and endogenous stresses and serves to render animals resistant to chemical carcinogenesis and other forms of toxicity, whilst disruption of the pathway exacerbates these outcomes. This pathway can be induced by thiol-reactive small molecules that demonstrate protective efficacy in preclinical chemoprevention models and in clinical trials. However, mutations and epigenetic modifications affecting the regulation and fate of NRF2 can lead to constitutive dominant hyperactivation of signaling that preserves rather than attenuates cancer phenotypes by providing selective resistance to stresses. This review provides a synopsis of KEAP1-NRF2 signaling, compares the impact of genetic versus pharmacologic activation and considers both the attributes and concerns of targeting the pathway in chemoprevention.

Biologically relevant exposure science for 21st century toxicity testing

High visibility efforts in toxicity testing and computational toxicology including the recent National Research Council of the National Academies (NRC) report, Toxicity Testing in the 21st Century: A Vision and Strategy (NRC, 2007a), raise important research questions and opportunities for the field of exposure science. The authors of the National Academies report (NRC, 2007a) emphasize that population-based data and human exposure information are required at each step of their vision for toxicity testing and that these data will continue to play a critical role in both guiding development and use of the toxicity information. In fact, state-of-the-art exposure science is essential for translation of toxicity data to assess potential for risk to individuals and populations and to inform public health decisions. As we move forward to implement the NRC vision, a transformational change in exposure science is required. Application of a fresh perspective and novel techniques to capture critical determinants at biologically motivated resolution for translation from controlled in vitro systems to the open multifactorial system of real-world human-environment interaction will be critical. Development of an exposure ontology and knowledge base will facilitate extension of network analysis to the individual and population for translating toxicity information and assessing health risk. Such a sea change in exposure science is required to incorporate consideration of lifestage, genetic susceptibility, and interaction of nonchemical stressors for holistic assessment of risk factors associated with complex environmental disease. A new generation of scientific tools has emerged to rapidly measure signals from cells, tissues, and organisms following exposure to chemicals. Investment in 21st century exposure science is now required to fully realize the potential of the NRC vision for toxicity testing.

Human aflatoxin albumin adducts quantitatively compared by ELISA, HPLC with fluorescence detection, and HPLC with isotope dilution mass spectrometry

Essential to the conduct of epidemiologic studies examining aflatoxin exposure and the risk of heptocellular carcinoma, impaired growth, and acute toxicity has been the development of quantitative biomarkers of exposure to aflatoxins, particularly aflatoxin B(1). In this study, identical serum sample sets were analyzed for aflatoxin-albumin adducts by ELISA, high-performance liquid chromatography (HPLC) with fluorescence detection (HPLC-f), and HPLC with isotope dilution mass spectrometry (IDMS). The human samples analyzed were from an acute aflatoxicosis outbreak in Kenya in 2004 (n = 102) and the measured values ranged from 0.018 to 67.0, nondetectable to 13.6, and 0.002 to 17.7 ng/mg albumin for the respective methods. The Deming regression slopes for the HPLC-f and ELISA concentrations as a function of the IDMS concentrations were 0.71 (r(2) = 0.95) and 3.3 (r(2) = 0.96), respectively. When the samples were classified as cases or controls, based on clinical diagnosis, all methods were predictive of outcome (P < 0.01). Further, to evaluate assay precision, duplicate samples were prepared at three levels by dilution of an exposed human sample and were analyzed on three separate days. Excluding one assay value by ELISA and one assay by HPLC-f, the overall relative SD were 8.7%, 10.5%, and 9.4% for IDMS, HPLC-f, and ELISA, respectively. IDMS was the most sensitive technique and HPLC-f was the least sensitive method. Overall, this study shows an excellent correlation between three independent methodologies conducted in different laboratories and supports the validation of these technologies for assessment of human exposure to this environmental toxin and carcinogen.

Pyrethroid pesticides and their metabolites in vacuum cleaner dust collected from homes and day-care centers

Urinary metabolites of pyrethroid pesticides have been used as biomarkers to estimate human exposure to the parent insecticide. It is important to establish whether these markers are present in environments or media to which humans are exposed routinely. Failure to account for the contribution of pre-existing markers to urinary concentrations could result in risk assessments that overestimate exposure. The purpose of this study was to quantify the concentrations of 13 selected pyrethroid pesticides and their degradation products in samples of indoor dust that had been collected in vacuum cleaner bags during the children's total exposure to persistent pesticides and other persistent organic pollutants (CTEPP) study of homes and day cares in North Carolina and Ohio. Sieved contents of 85 vacuum cleaner bags were analyzed, and permethrin was found in all samples. Sixty-nine samples contained at least one additional pyrethroid, but none contained more than five pyrethroids in detectable concentrations. Resmethrin, prallethrin, and fenpropathrin were not detected in any samples, while 36 contained phenothrin. The median concentration of permethrin in the samples was 1454ng/g of dust. Excluding permethrin, pyrethroid concentrations were typically less than or equal to 100ng/g of dust. The majority of degradates were present in more than half of the dust samples, usually at concentrations of less than or equal to 100ng/g of dust. For those pyrethroids with a characteristic oxydibenzene group, the cyclopropane degradates were present at higher concentrations than the corresponding benzoic acid moieties. Using urinary concentrations of these metabolites to model human exposure to the parent pyrethroids, may over-estimate risk due to the presence of pre-existing degradates in dust.

Role of biomarkers in monitoring exposures to chemicals: present position, future prospects

Biomarkers are becoming increasingly important in toxicology and human health. Many research groups are carrying out studies to develop biomarkers of exposure to chemicals and apply these for human monitoring. There is considerable interest in the use and application of biomarkers to identify the nature and amounts of chemical exposures in occupational and environmental situations. Major research goals are to develop and validate biomarkers that reflect specific exposures and permit the prediction of the risk of disease in individuals and groups. One important objective is to prevent human cancer. This review presents a commentary and consensus views about the major developments on biomarkers for monitoring human exposure to chemicals. A particular emphasis is on monitoring exposures to carcinogens. Significant developments in the areas of new and existing biomarkers, analytical methodologies, validation studies and field trials together with auditing and quality assessment of data are discussed. New developments in the relatively young field of toxicogenomics possibly leading to the identification of individual susceptibility to both cancer and non-cancer endpoints are also considered. The construction and development of reliable databases that integrate information from genomic and proteomic research programmes should offer a promising future for the application of these technologies in the prediction of risks and prevention of diseases related to chemical exposures. Currently adducts of chemicals with macromolecules are important and useful biomarkers especially for certain individual chemicals where there are incidences of occupational exposure. For monitoring exposure to genotoxic compounds protein adducts, such as those formed with haemoglobin, are considered effective biomarkers for determining individual exposure doses of reactive chemicals. For other organic chemicals, the excreted urinary metabolites can also give a useful and complementary indication of exposure for acute exposures. These methods have revealed 'backgrounds' in people not knowingly exposed to chemicals and the sources and significance of these need to be determined, particularly in the context of their contribution to background health risks.

Human biomonitoring and the INSPIRE directive: spatial data as link for environment and health research

Recently, there has been a rapid gain of interest in the availability, applicability, and integration of different types of spatial data for environment and health issues. The INSPIRE Directive (Directive 2007/2/EC) aims at providing better and easily accessible spatial information in Europe for the formulation and implementation of community policy on the environment by triggering the creation of a European spatial information infrastructure that delivers integrated spatial information services to potential users. Human biomonitoring (HBM) significantly contributes to the already existing data on environment and health because of its specific nature of providing information on the internal dose of chemicals rather than their mere presence in different environmental compartments. However, due to the intrinsic nature of HBM data, a number of issues need to be dealt with if HBM data are to be used to its full capacity in a geographic information systems (GIS) environment and within the INSPIRE directive. The current article highlights some of these issues, and discusses a number of options to improve the geographical relevance of HBM data for their optimal use within the INSPIRE Directive framework. The main aim of this publication is to illustrate that HBM has a significant contribution to make to the INSPIRE Directive, although some kind of data aggregation will be necessary to protect individual privacy. If HBM data wants to have a significant contribution to spatial information used to assist policymaking and on the surveillance or tracking of the direct or indirect impact of such policies, the HBM data need to be compatible with other data collected within the other themes of the INSPIRE Directive.

Dietary wheat reduction decreases the level of urinary deoxynivalenol in UK adults

In animals deoxynivalenol (DON) causes vomiting, feed refusal, growth retardation, and affects the immune system. DON is a common contaminant of wheat, however, validated biomarker data to assess exposure at the individual level and therefore any associated health effects are lacking. The development of a highly robust assay for urinary DON involving immunoaffinity (IAC) clean-up and liquid chromatography (LC)-mass spectrometric (MS) detection has allowed the assessment of (1) DON exposure within UK individuals and (2) a wheat intake intervention on urinary DON levels. Twenty-five volunteers from the United Kingdom (aged 21-59 years) completed semi-weighed food diaries on days 1 and 2 (normal diet), and a morning urine sample was provided on day 3. On days 3-6 (intervention), individuals restricted major sources of wheat intake following dietary guidance. Diaries were completed on days 5 and 6, and a further morning urine was provided on day 7. Urinary DON was measured following IAC clean-up and analysis by LC-MS. Wheat-based food intake (mean 322 g/day, range: 131-542 g/day), was significantly (P<0.001) reduced during the intervention to 26 g/day (range: 0-159 g/day) indicating good compliance. DON was detected in all 25 urine samples taken on day 3 (geometric mean 7.2 ng DON/mg creatinine (95% confidence interval (CI) 4.9-10.5 ng/mg), but following the intervention there was a significant 11-fold reduction (P<0.001) to 0.6 ng per mg (95% CI 0.4-0.9 ng/mg). These data are unique in demonstrating human exposure to DON in the United Kingdom using a urinary biomarker. Furthermore, the study demonstrates that exposure can be markedly reduced by avoiding wheat in the diet. On the basis of urinary biomarker levels some individuals are predicted to exceed current recommended daily intakes of DON, and thus the health consequences of these exposures merit further investigation.

Protective interventions to prevent aflatoxin-induced carcinogenesis in developing countries

The public health impact of aflatoxin exposure is pervasive in economically developing countries; consequently, we need to design intervention strategies for prevention that are practicable for these high-risk populations. The adverse health consequences of aflatoxins in populations are quite varied, eliciting acute effects, such as rapid death, and chronic outcomes, such as hepatocellular carcinoma. Furthermore, a number of epidemiological studies describe a variety of general adverse health effects associated with aflatoxin, such as impaired growth in children. Thus, the magnitude of the problem is disseminated across the entire spectrum of age, gender, and health status in the population. The aflatoxins multiplicatively increase the risk of liver cancer in people chronically infected with hepatitis B virus (HBV), which illustrates the deleterious impact that even low toxin levels in the diet can pose for human health. Thus other aflatoxin interactions, which likely contribute to the disease burden, still remain to be identified. Therefore, many diverse and appropriate strategies for disease prevention are needed to decrease the incidence of aflatoxin carcinogenesis in developing countries.

Modulation of aflatoxin biomarkers in human blood and urine by green tea polyphenols intervention

To evaluate the efficacy of green tea polyphenols (GTPs) in modulating aflatoxin B(1) (AFB(1)) biomarkers, a total of 352 serum samples and 352 urine samples collected from a 3 month chemoprevention trial with 500 mg GTPs, 1000 mg GTPs and a placebo were measured for AFB(1)-albumin adducts (AFB-AA), aflatoxin M(1) (AFM(1)) and aflatoxin B(1)-mercapturic acid (AFB-NAC). Levels of AFB-AA at baseline were comparable for all three dose groups (P = 0.506). No significant differences were observed in AFB-AA levels in the placebo group over the 3 month period (P = 0.252). However, a significant reduction in AFB-AA levels was observed in the 500 mg group (P = 0.002). A marginally significant reduction in AFB-AA levels was also found in the 1000 mg group over the 3 month intervention period (P = 0.051). An analysis using a mixed-effects model indicated that the reduction in AFB-AA levels over time was dose and time dependent (dose-time interaction P = 0.049). There were no significant differences in median AFM(1) levels among the three study groups at the baseline (P = 0.832), 1 month (P = 0.188) and 3 months (P = 0.132) of the GTP intervention; however, reduction of 42 and 43% in median AFM(1) levels, as compared with the placebo, were found in 500 mg (P = 0.096) and 1000 mg (P = 0.072) groups at 3 months of the intervention. Significant elevations in median AFB-NAC levels and the ratio of AFB-NAC:AFM(1) were found in both 500 and 1000 mg groups compared with the placebo group at both 1 month (P < 0.001) and 3 months (P < 0.001) of GTPs intervention. These results demonstrate that GTPs effectively modulate AFB(1) metabolism and metabolic activation.

Validation of fumonisin biomarkers in F344 rats

Fumonisins (FNs) are ubiquitous contaminants of cereal grains. Fumonisin B(1) (FB(1)) was linked to several animal and human diseases. To validate FB(1) biomarkers for studying human disease risks, F344 rats were administered by gavage with either a single dose of 0, 10 or 25 mg FB(1)/kg body weight (BW) or repeated doses of 0, 1.0, or 2.5 mg FB(1)/kg BW/day for 5 weeks. FB(1) excretion and FB(1)-induced metabolic alterations of sphingolipids in rat urine, feces and serum were assessed. Dose-dependent urinary and fecal excretion of free FB(1) were found in both single-dose- and repeat-dose-treated rats. In the single-dose study, urinary sphinganine (Sa) to sphingosine (So) ratio (Sa/So) reached a maximum at day 7 for the high-dose group and at day 5 for the low-dose group, whereas serum Sa/So showed only marginal changes. In the repeat-dose study, urinary Sa/So was persistently elevated at 2 weeks, while serum Sa/So was unchanged. Time course changes of sphinganine 1-phosphate (SaP) and sphingosine 1-phosphate (SoP) were also examined. Although serum Sa/So and SaP/SoP ratios showed no signs of time- or dose-dependent changes, a 10-fold increase in urinary SaP/SoP was observed, suggesting that urinary SaP/SoP is a more sensitive biomarker for FB(1) exposure. The accumulation of SaP and SoP was evident in the time course of SaP/Sa and SoP/So, which may reflect activity changes of enzymes closely related to the metabolism and catabolism of SaP and SoP. These results provide concrete evidence towards the practical use of excreted FB(1), Sa/So and SaP/SoP as biomarkers of exposure to FNs.

Analysis of DNA damage induced by aflatoxin B1 in Dunkin–Hartley guinea pigs

Aflatoxin B1 (AFB1) is among the most potent naturally occurring carcinogens and classified as a group I carcinogen. Since the ingestion of aflatoxin-contaminated food is associated with several liver diseases, the aim of the present study was to evaluate the effect of 2, 20, and 200 ppb of AFB1 on DNA damage in peripheral blood lymphocytes and liver cells in Dunkin-Hartley guinea pigs. The animals were divided into four groups according to the given diet. After the treatment the lymphocytes and liver cells were isolated and DNA damage determined by Comet assay. The levels of DNA damage in lymphocytes were higher animals treated with 200 ppb of AFB1-enriched diet (P = 0.02). In the liver cells there were a relationship between the levels of DNA damage and the consumption of AFB1 in all studied groups. These results suggest that Comet assay performed on lymphocytes is a valuable genotoxic marker for high levels of exposure to AFB1 in guinea pig. Additionally our results indicate that the exposure to this toxin increases significantly and increases the level of DNA damage in liver cells, which is a key step on liver cancer development. We also suggest that the Comet assay is an useful tool for monitoring the genotoxicity of AFB1 in liver.

Modulation of aflatoxin toxicity and biomarkers by lycopene in F344 rats

Modulation by lycopene of aflatoxin B(1) (AFB(1))-induced toxic effects, metabolism, and metabolic activations was studied in young F344 rats. Animals were pretreated orally with either corn oil (control group) or lycopene [100 mg/kg body weight (b.w.), intervention group] 5 days/week for 2 weeks. Control animals were then treated daily with AFB(1) (250 microg/kg b.w) alone. Intervention animals were administered lycopene (100 mg/kg b.w.) at 1 h following a daily treatment with AFB(1) (250 mug/kg b.w.). Pretreatment and intervention with lycopene significantly reduced the toxic effect caused by AFB(1) and greatly modulated AFB(1) metabolism and metabolic activation. Urinary excretion of AFB(1) phase 1 metabolites, AFM(1), AFQ(1), and AFP(1), was significantly decreased in lycopene-treated animals. Formation of serum AFB(1)-albumin adducts was also significantly reduced. The rate of reduction was from approximately 30% on day 1 (p<0.05) to 67.7% on day 15 (p<0.001). Lycopene intervention also significantly reduced formation of AFB(1)-DNA adducts in liver compared to control animals, with the highest reduction (52.7%) occurring on day 3 (p<0.05). Levels of AFB(1)-N(7)-guanine excreted in urine were also significantly decreased. Urinary excretion of the phase 2 detoxification metabolite, AFB(1)-mecapturic acid, was significantly increased in lycopene-intervened animals. AFB(1)-induced urinary excretion of 8-hydroxydeoxyguanosine was also reduced to 50% on day 7 after lycopene intervention. Collectively, these results suggest that inhibition of phase 1 metabolism and metabolic activation, as well as induction of phase 2 detoxification enzyme activity are the potential mechanisms for the chemopreventive effects of lycopene.

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.

Exposure to multiple environmental agents and their effect

INTRODUCTION

All children are exposed to multiple physical, chemical and biological challenges that can result in adverse health effects before and after birth. In this context, the danger of multiple exposures cannot be assessed from a single-chemical approach as used in classical toxicology.

AIM

To open up a 'negotiation space' for the problem of multiple exposure to environmental stressors, defined as any physical, chemical or biological entity that can induce an adverse response. In this context, two further questions obtain: to what extent can synergistic risks be assessed, and how far could potential adverse effects be prevented by enhanced regulation?

METHODS

A discussion of two general approaches is taken: 1) the investigation of mixtures such as smoking or air pollution without specifying the individual agents, and 2) the investigation of individual substances with a focus on possible interactions in the context of dose to receptor.

RESULTS

Although mixtures of compounds can have effects, it may not be possible to ascribe causation to a single compound. Furthermore, cumulative low-dose insult can, in some circumstances, be more toxic than a single high-dose exposure, e.g. endocrine disruptive effects of a combination of PCBs and dioxins which disrupt the thyroid hormone status; this tends to contradict elements of classical toxicology, . These cumulative insults may further combine with heavy metals and can disrupt the heme synthesis. It is possible that groups of pollutants could be used to test their cumulative capacity to multiple stress-susceptible receptor targets as is done in smoking and air pollution. This methodology could be used for further groups of potential pollutants, for example those associated with cleaning products, or cosmetics. Testing individual substances with a focus on interactions means that not only chemicals but also concurrent diseases should be taken into account. We suggest that the enhanced regulation of potential multiple stressors falls into two discrete categories. The first comprises a more precautionary approach (as demonstrated by the banning of chemicals such as some brominated flame retardants in Europe). The second comprises a more 'permissive' liberal approach involving the initial study of an individual compound, and subsequent interrogation of that compound in combination with another (as demonstrated by lowering the carcinogenicity of aflatoxin by vaccination against hepatitis B).

CONCLUSIONS

It is necessary to define and study groups of multiple stressors as in US EPA's Framework for Cumulative Risk Assessment (U.S. EPA 2003). Recent increased knowledge of the greater sensitivity of the unborn baby, the infant and the child, has led to general recognition that a higher degree of precaution is now needed in regulating for multiple stressors on the young. The more liberal permissive approach proceeding from established effects of the individual exposures is becoming less acceptable now that we know that there is much we do not understand about chronic effects of stressors during the early development phases. Conflicts over which approach to take may have to be resolved through engagement and negotiation with a wide community of stakeholders. This "community of interest" may include fundamental research scientists, practicing clinical paediatricians, patient groups, and others concerned with the health and wellbeing of infants and children.

Mycotoxin adducts on human serum albumin: biomarkers of exposure to Stachybotrys chartarum

OBJECTIVE

Despite the growing body of evidence showing adverse health effects from inhalation exposure to the trichothecene-producing mold Stachybotrys chartarum, controversy remains. Currently, there are no reliable assays suitable for clinical diagnosis of exposure. We hypothesized that satratoxin G (SG) -albumin adducts may serve as biomarkers of exposure to this fungus.

DESIGN

We studied the formation of adducts of SG with serum albumin in vitro using Western blots and mass spectrometry (MS) and searched for similar adducts formed in vivo using human and animal serum.

RESULTS

Samples of purified human serum albumin that had been incubated with increasing concentrations of SG showed concentration-dependent albumin bands in Western blots developed with anti-SG antibodies. MS analysis found that as many as 10 toxin molecules can be bound in vitro to one albumin molecule. The sequencing of albumin-adduct tryptic peptides and the analysis of pronase/aminopeptidase digests demonstrated that lysyl, cysteinyl, and histidyl residues are involved in the formation of these adducts. Serum samples from three patients with documented exposure to S. chartarum similarly revealed lysine-, cysteine-, and histidine-SG adducts after exhaustive digestion, affinity column enrichment, and MS analysis. These adducts were also found in the sera from rats exposed to the spores of S. chartarum in contrast to control human subjects and control animals.

CONCLUSIONS

These data document the occurrence of SG-albumin adducts in both in vitro experiments and in vivo human and animal exposures to S. chartarum.

RELEVANCE TO CLINICAL PRACTICE

SG-amino acid adducts may serve as reliable dosimeter biomarkers for detection of exposure to S. chartarum.

Proceedings of a workshop on DNA adducts: biological significance and applications to risk assessment Washington, DC, April 13-14, 2004

In April 2004, the Health and Environmental Sciences Institute, a branch of the International Life Sciences Institute, with support from the National Institute of Environmental Health Sciences, organized a workshop to discuss the biological significance of DNA adducts. Workshop speakers and attendees included leading international experts from government, academia, and industry in the field of adduct detection and interpretation. The workshop initially examined the relationship between measured adduct levels in the context of exposure and dose. This was followed by a discussion on the complex response of cells to deal with genotoxic insult in complex, interconnected, and interdependent repair pathways. One of the major objectives of the workshop was to address the recurring question about the mechanistic and toxicological relevance of low-concentration measured adducts and the presentations in the session entitled "Can low levels of DNA adducts predict adverse outcomes?" served as catalysts for further discussions on this subject during the course of the workshop. Speakers representing the regulatory community and industry reviewed the value, current practices, and limitations of utilizing DNA adduct data in risk assessment and addressed a number of practical questions pertaining to these issues. While no consensus statement emerged on the biological significance of low levels of DNA adducts, the workshop concluded by identifying the need for more experimental data to address this important question. One of the recommendations stemming from this workshop was the need to develop an interim "decision-logic" or framework to guide the integration of DNA adduct data in the risk assessment process. HESI has recently formed a subcommittee consisting of experts in the field and other key stakeholders to address this recommendation as well as to identify specific research projects that could help advance the understanding of the biological significance of low levels of DNA adducts.