Carbon black is an industrially produced particulate form of nearly pure elemental carbon. The ba... more Carbon black is an industrially produced particulate form of nearly pure elemental carbon. The basic building blocks of carbon black are (1) primary particles, minute pieces of matter with defined physical boundaries; (2) aggregates, collections of strongly bound or fused particles; and (3) agglomerates, collections of weakly bound aggregates. Industrial carbon black is produced within a closed reactor where the primary particles form aggregates, which become the indivisible entities of carbon black. These aggregates then form agglomerates, which are the typical form of carbon black in commerce. Carbon black is often used in in vitro and in vivo particle toxicology investigations as a reference nanoparticle. The toxicology studies often report the sizes of the primary particles but rarely the sizes of the aggregates or agglomerates. It appears in many cases that there is a limited understanding of the fact that carbon black typically does not exist as primary particles but instead exists as aggregates and agglomerates. Moreover, many toxicology studies manipulate carbon black particles in order to disperse them so that the form of carbon black used in these toxicology studies may be substantially different from the form that may be encountered in the workplace environment. Since the main exposure route for carbon black is inhalation, the question arose as to whether inhaled carbon black may deagglomerate or disaggregate to either smaller aggregates or primary particles when in contact with lung fluids. This question relates to the concern that there may be additional hazards of smaller particles, such as their ability to translocate to tissues and organs beyond the lung and the ability to pass through the blood-brain barrier. The purpose of this assessment is to review the existing literature for evidence as to whether carbon black deagglomerates or disaggregates into smaller aggregates or primary particles when in contact with lung fluid. On the basis of a review of the physical characteristics of commercial carbon black and various toxicology studies, it appears that commercially produced carbon black in contact with lung fluid is unlikely to deagglomerate or disaggregate into smaller aggregates or primary particles.
Organophosphate-based pesticides are widely used throughout the world. The acute effects of over-... more Organophosphate-based pesticides are widely used throughout the world. The acute effects of over-exposure to such compounds are well known. Concern has also been expressed that long-term exposure may result in damage to the nervous system. In a cross-sectional study, we compared neuropsychological performance in 146 sheep farmers who were exposed to organophosphates in the course of sheep dipping with 143 non-exposed quarry workers (controls). The farmers performed significantly worse than controls in tests to assess sustained attention and speed of information processing. These effects remained after adjustment for covariates. The farmers also showed greater vulnerability to psychiatric disorder than did the controls as measured by the General Health Questionnaire. There were no observed effects on short-term memory and learning. Repeated exposure to organophosphate-based pesticides appears to be associated with subtle changes in the nervous system. Measures should be taken to redu...
1. Incubation of human lymphocytes with sodium dichromate (CrVI) at 37 degrees C for 3 h resulted... more 1. Incubation of human lymphocytes with sodium dichromate (CrVI) at 37 degrees C for 3 h resulted in a dose-dependent increase in DNA strand breaks without concurrent cytotoxicity. In contrast, chromium acetate hydroxide (CrIII) failed to induce DNA strand breaks at sub-cytotoxic concentrations. 2. DNA strand breaks were also detected in the peripheral lymphocytes of Wistar rats, 24 h after intratracheal instillation of sodium dichromate (1.3 and 2.5 mg kg-1). Instillation of chromium acetate hydroxide (up to 21.8 mg kg-1) failed to induce DNA strand breaks in peripheral lymphocytes. In accord with previous studies, hexavalent chromium was found to be more readily absorbed from the lungs into the peripheral blood than chromium in its trivalent form. 3. The results of this study indicate that fluorometric analysis of DNA unwinding (FADU) in peripheral lymphocytes might be a convenient method of measuring an important biological effect of chromium in occupationally-exposed workers.
The aim of the current HBM-study is to further the understanding of the impact of inter- and intr... more The aim of the current HBM-study is to further the understanding of the impact of inter- and intra-individual variability in HBM surveys as it may have implications for the design and interpretation of the study outcomes. As spot samples only provide a snapshot in time of the concentrations of chemicals in an individual, it remains unclear to what extent intra-individual variability plays a role in the overall variability of population-wide HBM surveys. The current paper describes the results of an intensive biomonitoring study, in which all individual urine samples of 8 individuals were collected over a 6-day sampling period (a total of 352 unique samples). By analyzing different metals (As, Cd, Mn, Ni) in each individual sample, inter- and intra-individual variability for these four metals could be determined, and the relationships between exposure, internal dose, and sampling protocol assessed. Although the range of biomarker values for different metals was well within the normal range reported in large-scale population surveys, large intra-individual differences over a 6-day period could also be observed. Typically, measured biomarker values span at least an order of magnitude within an individual, and more if specific exposure episodes could be identified. Fish consumption for example caused a twenty- to thirty-fold increase in urinary As-levels over a period of 2-6h. Intra-class correlation coefficients (ICC) were typically low for uncorrected biomarker values (between 0.104 and 0.460 for the 4 metals), but improved when corrected for creatinine or specific gravity (SG). The results show that even though urine is a preferred matrix for HBM studies, there are certain methodological issues that need to be taken into account in the interpretation of urinary biomarker data, related to the intrinsic variability of the urination process itself, the relationship between exposure events and biomarker quantification, and the timing of sampling. When setting up HBM-projects, this expected relationship between individual exposure episode and urinary biomarker concentration needs to be taken into account.
International Journal of Hygiene and Environmental Health, 2013
Human biomonitoring (HBM) is a widely accepted tool to aid assessment of chemical uptake in risk ... more Human biomonitoring (HBM) is a widely accepted tool to aid assessment of chemical uptake in risk assessment. However, our understanding of the biological relevance of the results of HBM can be restricted, due in some part to the limited information on background environmental exposures and biomarker concentrations in the general population. The study described here specifically addresses the question of what constitutes normal background levels in the UK population of a number of biomarkers (the chemical itself or one of its stable metabolites) for a variety of environmental chemicals that are frequently encountered because of their widespread use. The environmental chemicals selected for this study were benzene, chlorinated hydrocarbons, dithiocarbamates, cadmium, mercury, naphthalene, diethylhexyl phthalate, synthetic pyrethroids and xylene. Volunteers (n=436) were randomly sought by a postal survey based on the UK Electoral Register. Participants were asked to complete a questionnaire and provide a urine sample. The overall response rate was 7.5%, with volunteers being recruited from all areas of the UK including, England, Scotland, Wales and Northern Ireland. Study participants were adults and comprised 45% male and 55% females. We have conducted a simple, postal-based, cost-effective study and generated similar reference values to very large surveys such as NHANES. This demonstrates that large investigations may not be necessary to get a reasonable idea of environmental exposures, especially in initial 'screening-type' investigations to identify particular exposures of concern or to demonstrate that exposures are reassuring low and that no further survey data needs to be gathered.
Carbon black is an industrially produced particulate form of nearly pure elemental carbon. The ba... more Carbon black is an industrially produced particulate form of nearly pure elemental carbon. The basic building blocks of carbon black are (1) primary particles, minute pieces of matter with defined physical boundaries; (2) aggregates, collections of strongly bound or fused particles; and (3) agglomerates, collections of weakly bound aggregates. Industrial carbon black is produced within a closed reactor where the primary particles form aggregates, which become the indivisible entities of carbon black. These aggregates then form agglomerates, which are the typical form of carbon black in commerce. Carbon black is often used in in vitro and in vivo particle toxicology investigations as a reference nanoparticle. The toxicology studies often report the sizes of the primary particles but rarely the sizes of the aggregates or agglomerates. It appears in many cases that there is a limited understanding of the fact that carbon black typically does not exist as primary particles but instead exists as aggregates and agglomerates. Moreover, many toxicology studies manipulate carbon black particles in order to disperse them so that the form of carbon black used in these toxicology studies may be substantially different from the form that may be encountered in the workplace environment. Since the main exposure route for carbon black is inhalation, the question arose as to whether inhaled carbon black may deagglomerate or disaggregate to either smaller aggregates or primary particles when in contact with lung fluids. This question relates to the concern that there may be additional hazards of smaller particles, such as their ability to translocate to tissues and organs beyond the lung and the ability to pass through the blood-brain barrier. The purpose of this assessment is to review the existing literature for evidence as to whether carbon black deagglomerates or disaggregates into smaller aggregates or primary particles when in contact with lung fluid. On the basis of a review of the physical characteristics of commercial carbon black and various toxicology studies, it appears that commercially produced carbon black in contact with lung fluid is unlikely to deagglomerate or disaggregate into smaller aggregates or primary particles.
Organophosphate-based pesticides are widely used throughout the world. The acute effects of over-... more Organophosphate-based pesticides are widely used throughout the world. The acute effects of over-exposure to such compounds are well known. Concern has also been expressed that long-term exposure may result in damage to the nervous system. In a cross-sectional study, we compared neuropsychological performance in 146 sheep farmers who were exposed to organophosphates in the course of sheep dipping with 143 non-exposed quarry workers (controls). The farmers performed significantly worse than controls in tests to assess sustained attention and speed of information processing. These effects remained after adjustment for covariates. The farmers also showed greater vulnerability to psychiatric disorder than did the controls as measured by the General Health Questionnaire. There were no observed effects on short-term memory and learning. Repeated exposure to organophosphate-based pesticides appears to be associated with subtle changes in the nervous system. Measures should be taken to redu...
1. Incubation of human lymphocytes with sodium dichromate (CrVI) at 37 degrees C for 3 h resulted... more 1. Incubation of human lymphocytes with sodium dichromate (CrVI) at 37 degrees C for 3 h resulted in a dose-dependent increase in DNA strand breaks without concurrent cytotoxicity. In contrast, chromium acetate hydroxide (CrIII) failed to induce DNA strand breaks at sub-cytotoxic concentrations. 2. DNA strand breaks were also detected in the peripheral lymphocytes of Wistar rats, 24 h after intratracheal instillation of sodium dichromate (1.3 and 2.5 mg kg-1). Instillation of chromium acetate hydroxide (up to 21.8 mg kg-1) failed to induce DNA strand breaks in peripheral lymphocytes. In accord with previous studies, hexavalent chromium was found to be more readily absorbed from the lungs into the peripheral blood than chromium in its trivalent form. 3. The results of this study indicate that fluorometric analysis of DNA unwinding (FADU) in peripheral lymphocytes might be a convenient method of measuring an important biological effect of chromium in occupationally-exposed workers.
The aim of the current HBM-study is to further the understanding of the impact of inter- and intr... more The aim of the current HBM-study is to further the understanding of the impact of inter- and intra-individual variability in HBM surveys as it may have implications for the design and interpretation of the study outcomes. As spot samples only provide a snapshot in time of the concentrations of chemicals in an individual, it remains unclear to what extent intra-individual variability plays a role in the overall variability of population-wide HBM surveys. The current paper describes the results of an intensive biomonitoring study, in which all individual urine samples of 8 individuals were collected over a 6-day sampling period (a total of 352 unique samples). By analyzing different metals (As, Cd, Mn, Ni) in each individual sample, inter- and intra-individual variability for these four metals could be determined, and the relationships between exposure, internal dose, and sampling protocol assessed. Although the range of biomarker values for different metals was well within the normal range reported in large-scale population surveys, large intra-individual differences over a 6-day period could also be observed. Typically, measured biomarker values span at least an order of magnitude within an individual, and more if specific exposure episodes could be identified. Fish consumption for example caused a twenty- to thirty-fold increase in urinary As-levels over a period of 2-6h. Intra-class correlation coefficients (ICC) were typically low for uncorrected biomarker values (between 0.104 and 0.460 for the 4 metals), but improved when corrected for creatinine or specific gravity (SG). The results show that even though urine is a preferred matrix for HBM studies, there are certain methodological issues that need to be taken into account in the interpretation of urinary biomarker data, related to the intrinsic variability of the urination process itself, the relationship between exposure events and biomarker quantification, and the timing of sampling. When setting up HBM-projects, this expected relationship between individual exposure episode and urinary biomarker concentration needs to be taken into account.
International Journal of Hygiene and Environmental Health, 2013
Human biomonitoring (HBM) is a widely accepted tool to aid assessment of chemical uptake in risk ... more Human biomonitoring (HBM) is a widely accepted tool to aid assessment of chemical uptake in risk assessment. However, our understanding of the biological relevance of the results of HBM can be restricted, due in some part to the limited information on background environmental exposures and biomarker concentrations in the general population. The study described here specifically addresses the question of what constitutes normal background levels in the UK population of a number of biomarkers (the chemical itself or one of its stable metabolites) for a variety of environmental chemicals that are frequently encountered because of their widespread use. The environmental chemicals selected for this study were benzene, chlorinated hydrocarbons, dithiocarbamates, cadmium, mercury, naphthalene, diethylhexyl phthalate, synthetic pyrethroids and xylene. Volunteers (n=436) were randomly sought by a postal survey based on the UK Electoral Register. Participants were asked to complete a questionnaire and provide a urine sample. The overall response rate was 7.5%, with volunteers being recruited from all areas of the UK including, England, Scotland, Wales and Northern Ireland. Study participants were adults and comprised 45% male and 55% females. We have conducted a simple, postal-based, cost-effective study and generated similar reference values to very large surveys such as NHANES. This demonstrates that large investigations may not be necessary to get a reasonable idea of environmental exposures, especially in initial 'screening-type' investigations to identify particular exposures of concern or to demonstrate that exposures are reassuring low and that no further survey data needs to be gathered.
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