Creatinine and specific gravity normalization in biological monitoring of occupational exposures.

Reference values for the biological monitoring of occupational exposures are generally normalized on the basis of creatinine (CR) concentration or specific gravity (SG) to account for fluctuations in urine dilution. For instance, the American Conference of Governmental Industrial Hygienists (ACGIH(®)) uses a reference value of 1g/L for CR. The comparison of urinary concentrations of biomarkers between studies requires the adjustment of results based on a reference CR and/or SG value, although studies have suggested that age, sex, muscle mass, and time of the day can exert non-negligible influences on CR excretion, while SG appears to be less affected.

Rat pulmonary responses to inhaled nano-TiO₂: effect of primary particle size and agglomeration state.

Background: The exact role of primary nanoparticle (NP) size and their degree of agglomeration in aerosols on the determination of pulmonary effects is still poorly understood. Smaller NP are thought to have greater biological reactivity, but their level of agglomeration in an aerosol may also have an impact on pulmonary response. The aim of this study was to investigate the role of primary NP size and the agglomeration state in aerosols, using well-characterized TiO₂ NP, on their relative pulmonary toxicity, through inflammatory, cytotoxic and oxidative stress effects in Fisher 344 male rats.

Identification of workers exposed concomitantly to heat stress and chemicals.

In the context of climate change, concomitant exposure to heat stress and chemicals takes on great importance. However, little information is available in this regard. The purpose of this research, therefore, was to develop an approach aimed at identifying worker groups that would be potentially most at risk.

Assessment of the contribution of electron microscopy to nanoparticle characterization sampled with two cascade impactors.

This study assessed the contribution of electron microscopy to the characterization of nanoparticles and compared the degree of variability in sizes observed within each stage when sampled by two cascade impactors: an Electrical Low Pressure Impactor (ELPI) and a Micro-Orifice Uniform Deposit Impactor (MOUDI). A TiO(2) nanoparticle (5 nm) suspension was aerosolized in an inhalation chamber. Nanoparticles sampled by the impactors were collected on aluminum substrates or TEM carbon-coated copper grids using templates, specifically designed in our laboratories, for scanning and transmission electron microscopy (SEM, TEM) analysis, respectively.

Generating nano-aerosols from TiO₂ (5 nm) nanoparticles showing different agglomeration states. Application to toxicological studies.

Agglomeration of nanoparticles (NP) is a key factor in the generation of aerosols from nano-powders and may represent an important parameter to consider in toxicological studies. For this reason, the characterization of NP aerosols (e.g.

Immunotoxicity of 3 chemical forms of beryllium following inhalation exposure.

The toxicity of 3 chemical forms of beryllium (Be) was compared in this study. A total of 160 mice equally divided into 4 groups were exposed by inhalation (nose only) for 3 consecutive weeks, 5 d/week, 6 h/d. One group was used as control, while the 3 others were exposed to fine particles of Be metal, Be oxide (BeO), or Be aluminum (BeAl).

Development and validation of analytical methods for ultra-trace beryllium in biological matrices.

Beryllium (Be) is still not well understood from a toxicological point of view, and studies that involve the determination of different Be compounds species in tissues need to be conducted. In this paper we describe the development and validation of reliable methods for the detection of ultra-trace levels of Be in various biological matrices. Blood and tissues (liver, lung, spleen, and kidney) were used in this study.

Urinary levels, tissue concentrations and lung inflammation after nose-only exposure to three different chemical forms of beryllium.

This study aimed to determine the toxicity and toxicokinetic of three Be chemical species A total of 120 mice (four groups of 30) were nose-only exposed. The first group was used as a control while the three others were exposed to 250 microg m(-3) of fine particles of three different Be species (Be metal, Be-F; Be oxide, BeO-F; Be aluminium, BeAl-F). Exposure lasted over three consecutive weeks, five days per week and 6 h per day.

Beryllium contamination and exposure monitoring in an inhalation laboratory setting.

Beryllium (Be) is used in several forms: pure metal, beryllium oxide, and as an alloy with copper, aluminum, or nickel. Beryllium oxide, beryllium metal, and beryllium alloys are the main forms present in the workplace, with inhalation being the primary route of exposure. Cases of workers with sensitization or chronic beryllium disease challenge the scientific community for a better understanding of Be toxicity.

Effect of physical exertion on the biological monitoring of exposure to various solvents following exposure by inhalation in human volunteers: III. Styrene.

This study evaluated the impact of different work load intensities on biological indicators of styrene exposure. Four adult Caucasian men, aged 20 to 44 years, were recruited. Groups of 2-4 volunteers were exposed to 20 ppm of styrene in an exposure chamber according to scenarios involving either aerobic, muscular, or both types of physical exercise for 3 or 7 hr.

The effect of workload on biological monitoring of occupational exposure to toluene and n-Hexane: contribution of physiologically based toxicokinetic modeling.

A physiologically based toxicokinetic model was used to examine the impact of work load on the relationship between the airborne concentrations and exposure indicator levels of two industrial solvents, toluene and n-Hexane. The authors simulated occupational exposure (8 hr/day, 5 days/week) at different concentrations, notably 20 ppm and 50 ppm, which are the current threshold limit values recommended by ACGIH for toluene and n-hexane, respectively. Different levels of physical activity, namely, rest, 25 W, and 50 W (for 12 hr followed by 12 hr at rest) were simulated to assess the impact of work load on the recommended biological exposure indices: toluene in blood prior to the last shift of the workweek, urinary o-cresol (a metabolite of toluene) at the end of the shift, and free (nonhydrolyzed) 2,5-hexanedione (a metabolite of n-hexane) at the end of the shift at the end of the workweek.

Immunological responses in C3H/HeJ mice following nose-only inhalation exposure to different sizes of beryllium metal particles.

Beryllium is used in a wide variety of industries. Chronic beryllium disease is the most common occupational disease among workers following exposure to Be. The objective of this study was to determine the immunologic effects of two different particle sizes of Be metal, <2.

Effect of physical exertion on the biological monitoring of exposure to various solvents following exposure by inhalation in human volunteers: II. n-Hexane.

This study evaluated the impact of physical exertion on two n-hexane (HEX) exposure indicators in human volunteers exposed under controlled conditions in an inhalation chamber. A group of four volunteers (two women, two men) were exposed to HEX (50 ppm; 176 mg/m(3)) according to several scenarios involving several periods when volunteers performed either aerobic (AERO), muscular (MUSC), or both AERO/MUSC types of exercise. The target intensities for 30-min exercise periods separated by 15-min rest periods were the following: REST, 50W AERO [time-weighted average intensity including resting period (TWAI): 38W], 50W AERO/MUSC (TWAI: 34W), 100W AERO/MUSC (TWAI: 63W), and 100W AERO (TWAI: 71W) for 7 hr (two 3-hr exposure periods separated by 1 hr without exposure) and 50W MUSC for 3 hr (TWAI: 31W).

A web tool for the identification of potential interactive effects of chemical mixtures.

This project was undertaken to develop a toxicological database allowing the identification of possible additive or other interactive effects of mixtures present in the work environment. In the first phase of the project, whose findings have already been published, critical toxicological data were compiled for each of the 695 chemical substances in the Quebec Occupational Health Regulation, allowing the prediction of potential additivity among components of a mixture. In the second phase of this project, the types of interactions for mixtures most likely to be found in workplaces and for which primary literature data are available were specified.

Effect of physical exertion on the biological monitoring of exposure of various solvents following exposure by inhalation in human volunteers: I. Toluene.

Physical exertion (work load) has been recognized as one of several factors that can influence the kinetics of xenobiotics within the human body. This study was undertaken to evaluate the impact of physical exertion on two exposure indicators of toluene (TOL) in human volunteers exposed under controlled conditions in an inhalation chamber. A group of four volunteers (one woman, three men) were exposed to TOL (50 ppm) according to the following scenarios involving several periods during which volunteers were asked to perform either aerobic (AERO), muscular (MUSC), or both (AERO/MUSC) types of physical exercise (exercise bicycle, treadmills, pulleys).

Biological exposure indicators: quantification of biological variability using toxicokinetic modeling.

Compartmental and physiologically based toxicokinetic modeling coupled with Monte Carlo simulation were used to quantify the impact of biological variability (physiological, biochemical, and anatomic parameters) on the values of a series of bio-indicators of metal and organic industrial chemical exposures. A variability extent index and the main parameters affecting biological indicators were identified. Results show a large diversity in interindividual variability for the different categories of biological indicators examined.

Database for the toxicological evaluation of mixtures in occupational atmospheres.

Workers are regularly simultaneously exposed to multiple chemical substances. As in the ACGIH (American Conference of Governmental Industrial Hygienists) approach, the Québec Regulation prescribes that when two or more hazardous substances are present in workplaces and have similar effects on the same organs of the human body, their effects should be considered additive, unless established otherwise. This project was undertaken to develop a user-friendly toxicological database aid in identification of possible interactive effects of mixtures present in the work environment.

Impact of human variability on the biological monitoring of exposure to toluene, phenol, lead, and mercury: II. Compartmental based toxicokinetic modelling.

In order to quantify the effect of human variability on a wide range of biological exposure indicators (EIs), a general compartmental model was developed and tested on several chemicals. The model consists of four compartments. In a first step, it was applied to four chemicals: toluene (TOL), phenol (Ph), lead (Pb), and mercury (Hg).

Impact of human variability on the biological monitoring of exposure to toluene: I. Physiologically based toxicokinetic modelling.

Using an approach involving physiologically based toxicokinetic (PBTK) modelling and Monte Carlo simulation (MCS), we investigated the impact of the biological variability affecting the parameters (e.g. physiological, physicochemical, biochemical) which determine toluene (TOL) kinetics on two exposure indicators (EIs): urinary excretion of o-cresol (o-CR), measured at the end of an 8 h exposure at 50 ppm, and unchanged TOL in blood (B-TOL) sampled prior to the last shift of a 5 day workweek.