To what extent are biomonitoring data available in chemical risk assessment?

Chromosomal changes induced in mouse bone marrow cells following six weeks inhalation of cyclohexanol

The effects of low doses of cyclohexanol exposure were studied in mouse bone marrow cells including chromosome aberrations (CA), micronucleus (MN) and sister chromatid exchanges (SCE) as biomarkers. Capillaries with a tested agent that was evaporated continuously were placed in an experimental chamber for six weeks. No clastogenic and/or aneugenic effect of CA and MN induction was observed. A significant elevation of induced damage was achieved in the SCE study (p < 0.001) that has confirmed the early exposure of cyclohexanol to mice.

Temporal stability of the conjugated species of bisphenol A, parabens, and other environmental phenols in human urine

Human exposure to environmental phenols can be assessed by measuring the urinary concentrations of these compounds or their metabolites. Total concentrations, which include both free and conjugated (i.e., glucuronide and sulfated) species, are usually reported. Because conjugation may reduce the potential bioactivity of the compounds, measuring separately both the concentrations of free and conjugated species can be of interest. Data on the stability of these conjugated species in urine is critical if the concentrations of free and conjugated species are to be compared. Over a period of 6 months, we investigated the stability of the urinary conjugates of eight environmental phenols (bisphenol A, 2-hydroxy-4-metoxybenzophenone or benzophenone-3, triclosan, 2,5-dichlorophenol, methyl paraben, ethyl paraben, propyl paraben, and butyl paraben) at three storage conditions (room temperature, 4 degrees C, and -70 degrees C). After collection, conjugated species appeared to be stable for at least 7 days when the urine was stored at 4 degrees C, and for at least 180 days at -70 degrees C. By contrast, some of the environmental phenol conjugates commenced to degrade within 24 h after collection when the urine was stored at room temperature although the total concentrations remained relatively constant for at least 30 days. These results suggest that if the concentrations of free and conjugated species will be used for exposure assessment purposes, urine specimens collected for analysis of environmental phenols should be kept at room temperature for the shortest possible time after collection.

Combined effects of exposure to styrene and ethanol on the auditory function in the rat

In order to study the auditory effects of a metabolic interaction between ethanol and styrene, a first group of rats was gavaged once a day with ethanol (4 g/kg), a second group was exposed to 750 ppm styrene by inhalation, and a third group was exposed to both ethanol and styrene (5 days/week, 4 weeks). Auditory function was tested by recording brainstem (inferior colliculus) auditory evoked potentials, and cochlear hair cell loss was estimated by light microscopy. Cytochrome P450 2E1 and the main urinary styrene metabolites, namely mandelic, phenylglyoxylic and hippuric acids, were measured by high-performance liquid chromatography to check the effects of ethanol on styrene metabolism. In our experimental conditions, ethanol alone did not have any effect on auditory sensitivity, whereas styrene alone caused permanent threshold shifts and outer hair cell damage. Hearing and outer hair cell losses were larger after the exposure to both ethanol and styrene than those induced by styrene alone, indicating a clear potentiation of styrene ototoxicity by ethanol. As expected, metabolic data showed that ethanol alters styrene metabolism and can therefore be considered a modifying factor of styrene toxicokinetics.

Association between 8-hydroxy-2'-deoxyguanosine levels in DNA of workers highly exposed to asbestos and their clinical data, occupational and non-occupational confounding factors, and cancer

In the preceding paper [B. Marczynski, P. Rozynek, T. Kraus, St. Schlösser, H.J. Raithel, X. Baur, Levels of 8-hydroxy-2'-deoxyguanosine in DNA of white blood cells from workers highly exposed to asbestos in Germany, Mutat. Res. (2000) submitted] we described significant increases (p<0.001) in the levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) adducts in the DNA of white blood cells (WBC) of workers highly exposed to asbestos fibers at the workplace relative to those found in the control group in all three study years (period between 1994 and 1997). The results show that the oxidative DNA damage in exposed individuals is between 1.7 times and twice that found in control samples for all 3 years of the study (p<0.001). The aim of this study was to examine the association between the 8-OHdG levels in WBC DNA of workers highly exposed to asbestos fibers at the workplace and clinical data, occupational and non-occupational confounding factors, and cancer. There is no obvious correlation between the steady-state levels of 8-OHdG in the circulating WBC DNA of asbestos workers and possible confounding factors, such as the presence of benign asbestos-associated diseases, the duration of asbestos exposure, the latency period, the fixed cumulative fibrous dust dose ("fiber years"), age, smoking status, acute febrile infections, medicines, aspirin, calcium (Ca(2+)), magnesium (Mg(2+)), and the hormone and vitamin intake. This indicates that previous inhalation of asbestos fibers is the major factor responsible for the difference observed in oxidative DNA damage between asbestos workers and controls. For patients suffering from respiratory cancer, cancer of the gastrointestinal tract, mouth/pharynx/larynx, and urogenital tract the mean DNA-adduct level was significantly higher (p<0.01) than that found in controls, but not significantly higher (p>0.05) than that for asbestos-exposed patients without tumours. The formation of 8-OHdG adduct levels in WBC DNA of patients with hematopoietic cancer, chondrosarcomas and multiform glioblastomas was not significantly higher than that found in the control group (p>0.05). Our results support the hypothesis that oxidative DNA damage in man caused by asbestos fibers plays a role in the formation of malignant tumours.