Biological effects of carbon black nanoparticles are changed by surface coating with polycyclic aromatic hydrocarbons.

BACKGROUND: Carbon black nanoparticles (CBNP) are mainly composed of carbon, with a small amount of other elements (including hydrogen and oxygen). The toxicity of CBNP has been attributed to their large surface area, and through adsorbing intrinsically toxic substances, such as polycyclic aromatic hydrocarbons (PAH). It is not clear whether a PAH surface coating changes the toxicological properties of CBNP by influencing their physicochemical properties, through the specific toxicity of the surface-bound PAH, or by a combination of both. METHODS: Printex®90 (P90) was used as CBNP; the comparators were P90 coated with either benzo[a]pyrene (BaP) or 9-nitroanthracene (9NA), and soot from acetylene combustion that bears various PAHs on the surface (AS-PAH). Oxidative stress and IL-8/KC mRNA expression were determined in A549 and bronchial epithelial cells (16HBE14o-, Calu-3), mouse intrapulmonary airways and tracheal epithelial cells. Overall toxicity was tested in a rat inhalation study according to Organization for Economic Co-operation and Development (OECD) criteria. Effects on cytochrome monooxygenase (Cyp) mRNA expression, cell viability and mucociliary clearance were determined in acute exposure models using explanted murine trachea. RESULTS: All particles had similar primary particle size, shape, hydrodynamic diameter and ζ-potential. All PAH-containing particles had a comparable specific surface area that was approximately one third that of P90. AS-PAH contained a mixture of PAH with expected higher toxicity than BaP or 9NA. PAH-coating reduced some effects of P90 such as IL-8 mRNA expression and oxidative stress in A549 cells, granulocyte influx in the in vivo OECD experiment, and agglomeration of P90 and mucus release in the murine trachea ex vivo. Furthermore, P90-BaP decreased particle transport speed compared to P90 at 10 µg/ml. In contrast, PAH-coating induced IL-8 mRNA expression in bronchial epithelial cell lines, and Cyp mRNA expression and apoptosis in tracheal epithelial cells. In line with the higher toxicity compared to P90-BaP and P90-9NA, AS-PAH had the strongest biological effects both ex vivo and in vivo. CONCLUSIONS: Our results demonstrate that the biological effect of CBNP is determined by a combination of specific surface area and surface-bound PAH, and varies in different target cells.

Desktop exposure system and dosimetry for small scale in vivo radiofrequency exposure experiments.

This paper describes a new approach to the risk assessment of exposure from wireless network devices, including an exposure setup and dosimetric assessment for in vivo studies. A novel desktop reverberation chamber has been developed for well-controlled exposure of mice for up to 24 h per day to address the biological impact of human exposure scenarios by wireless networks. The carrier frequency of 2.45 GHz corresponds to one of the major bands used in data communication networks and is modulated by various modulation schemes, including Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Radio Frequency Identification (RFID), and wireless local area network, etc. The system has been designed to enable exposures of whole-body averaged specific absorption rate (SAR) of up to 15 W/kg for six mice of an average weight of 25 g or of up to 320 V/m incident time-averaged fields under loaded conditions without distortion of the signal. The dosimetry for whole-body SAR and organ-averaged SAR of the exposed mice, with analysis of uncertainty and variation analysis, is assessed. The experimental dosimetry based on temperature measurement agrees well with the numerical dosimetry, with a very good SAR uniformity of 0.4 dB in the chamber. Furthermore, a thermal analysis and measurements were performed to provide better understanding of the temperature load and distribution in the mice during exposure.

Change in agglomeration status and toxicokinetic fate of various nanoparticles in vivo following lung exposure in rats.

The deposition characteristics in lungs following inhalation, the potential toxic effects induced and the toxicokinetic fate including a possible translocation to other sites of the body are predominantly determined by the agglomeration status of nanoscaled primary particles. Systemic particle effects, i.e. effects on remote organs besides the respiratory tract are considered to be of relevant impact only for de-agglomerated particles with a nanoscaled aspect. Rats were exposed to various types of nanoscaled particles, i.e. titanium dioxide, carbon black and constantan. These were dispersed in physiologically compatible media, e.g. phosphate buffer, sometimes including auxiliaries. Rats were treated with aqueous nanoparticle dispersions by intratracheal instillation or were exposed to well-characterized nanoparticle aerosols. Subsequently, alterations in the particle size distribution were studied using transmission electron microscopy (TEM) as well as the bronchoalveolar lavage (BAL) technique. Based on the results in various approaches, a tendency of nanoscaled particles to form larger size agglomerates following deposition and interaction with cells or the respiratory tract is predominant. The contrary trend, i.e. the increase of particle number due to a disintegration of agglomerates seems not to be of high relevance.

Indication of cocarcinogenic potential of chronic UMTS-modulated radiofrequency exposure in an ethylnitrosourea mouse model.

PURPOSE: To evaluate putative effects on tumour susceptibility in mice exposed to a UMTS (universal mobile telecommunications system) test signal for up to 24 months, commencing with embryo-fetal exposure. MATERIAL AND METHODS: Animals were exposed to UMTS fields with intensities of 0, 4.8, and 48 W/m(2), the low-dose group (4.8 W/m(2)) was subjected to additional prenatal ethylnitrosourea treatment (40 mg ENU/kg body weight). RESULTS: The high-level UMTS exposure (48 W/m(2)), the sham exposure, and the cage control groups showed comparable tumour incidences in the protocol organs. In contrast, the ENU-treated group UMTS-exposed at 4.8 W/m(2) displayed an enhanced lung tumour rate and an increased incidence of lung carcinomas as compared to the controls treated with ENU only. Furthermore, tumour multiplicity of the lung carcinomas was increased and the number of metastasising lung tumours was doubled in the ENU/UMTS group as compared to the ENU control group. CONCLUSION: This pilot study indicates a cocarcinogenic effect of lifelong UMTS exposure (4.8 W/m(2)) in female B6C3F1 descendants subjected to pretreatment with ethylnitrosourea.

Genotoxicity testing of sulfur dioxide (SO2) in a mouse bone marrow micronucleus test complemented with hematological endpoints.

Sulfur dioxide (SO2) is a non-flammable, non-explosive, colorless gas. It is a ubiquitous environmental pollutant and an important chemical intermediate in several industrial processes. The toxicological properties of SO2, including its genotoxic potential, have been studied extensively. The majority of the available in vitro data indicate a lack of genotoxicity of SO2, while for sulfite salts some positive results have been reported. However, recent in vivo studies, using Kunming albino mice, have pointed to in vivo clastogenicity of SO2. To re-evaluate these positive findings, a bone-marrow micronucleus test according to OECD Guideline No. 474 was performed. NMRI mice (m/f) were exposed by inhalation via whole-body exposure to 0 (clean air), 2.7, 8, 27, or 80mg/m3 (0, 1, 3, 10, or 30ppm) SO2 for 4h/day on 7 consecutive days. Animals were sacrificed 24h after start of the last exposure, and blood samples (for complementing hematology) and bone marrow smears (for analysis of micronuclei) were prepared. Under the conditions used, exposure to SO2 caused no acute toxicity, mortality, or reduction in body weight. Compared with the clean-air controls, hematological parameters such as hematocrit, hemoglobin, erythrocyte/platelet/total leukocyte counts, differential white blood cell counts, and indicators of blood formation (reticulocyte counts, ratio of polychromatic to normochromatic erythrocytes in the bone marrow) remained unchanged by SO2 treatment. Unlike the previously reported studies on micronucleus formation, SO2 did not induce micronuclei in polychromatic erythrocytes of the bone marrow, whereas the positive control cyclophosphamide (60mg/kg body weight) was quite effective in this respect. Interestingly, SO2 treatment significantly enhanced malondialdehyde levels in erythrocyte lysates (TBARS method), indicating SO2-mediated oxidative stress, but also demonstrating systemic availability of the inhaled SO2. In conclusion, the present study could not reproduce the genotoxicity findings of the previously reported studies. SO2 is thus considered non-genotoxic in polychromatic erythrocytes in the bone marrow of NMRI mice under the conditions and in the concentrations used.

Absence of genotoxic potential of 902 MHz (GSM) and 1747 MHz (DCS) wireless communication signals: In vivo two-year bioassay in B6C3F1 mice.

PURPOSE: The aim of the present investigation was to determine the incidence of micronuclei in peripheral blood erythrocytes of B6C3F1 mice that had been chronically exposed to radiofrequencies (RF) used for mobile communication. MATERIALS AND METHODS: 'Ferris wheels' were used to expose tube-restrained male and female mice to simulated environmental RF signals of the Global System for Mobile Communications (GSM, 902 MHz) or Digital Cellular System (DCS, 1747 MHz). RF signals were applied to the mice for 2 hours/day on 5 days/week for two years, at maximal whole-body-averaged specific absorption rates of 0.4, 1.3, and 4.0 W/kg body weight. Concurrent sham-exposed mice, cage controls, and positive controls injected with mitomycin C were included in this investigation. At necropsy, peripheral blood smears were prepared, and coded slides were stained using May-Grunwald-Giemsa or acridine orange. The incidence of micronuclei was recorded for each mouse in 2000 polychromatic and 2000 normochromatic erythrocytes. RESULTS: There were no significant differences in the frequency of micronuclei between RF-exposed, sham-exposed, and cage control mice, irrespective of the staining/counting method used. Micronuclei were, however, significantly increased in polychromatic erythrocytes of the positive control mice. CONCLUSIONS: In conclusion, the data did not indicate RF-induced genotoxicity in mice after two years of exposure.

Carcinogenicity study of GSM and DCS wireless communication signals in B6C3F1 mice.

The purpose of this study using a total of 1170 B6C3F1 mice was to detect and evaluate possible carcinogenic effects in mice exposed to radio-frequency-radiation (RFR) from Global System for Mobile Communication (GSM) and Digital Personal Communications System (DCS) handsets as emitted by handsets operating in the center of the communication band, that is, at 902 MHz (GSM) and 1747 MHz (DCS). Restrained mice were exposed for 2 h per day, 5 days per week over a period of 2 years to three different whole-body averaged specific absorption rate (SAR) levels of 0.4, 1.3, 4.0 mW/g bw (SAR), or were sham exposed. Regarding the organ-related tumor incidence, pairwise Fisher's test did not show any significant increase in the incidence of any particular tumor type in the RF exposed groups as compared to the sham exposed group. Interestingly, while the incidences of hepatocellular carcinomas were similar in EMF and sham exposed groups, in both studies the incidences of liver adenomas in males decreased with increasing dose levels; the incidences in the high dose groups were statistically significantly different from those in the sham exposed groups. Comparison to published tumor rates in untreated mice revealed that the observed tumor rates were within the range of historical control data. In conclusion, the present study produced no evidence that the exposure of male and female B6C3F1 mice to wireless GSM and DCS radio frequency signals at a whole body absorption rate of up to 4.0 W/kg resulted in any adverse health effect or had any cumulative influence on the incidence or severity of neoplastic and non-neoplastic background lesions, and thus the study did not provide any evidence of RF possessing a carcinogenic potential.

Maternal effects and cancer risk in the progeny of mice exposed to X-rays before conception.

To investigate in an animal model whether preconceptual X-ray exposure leads to an altered tumor rate and spectrum in the offspring, a transgeneration carcinogenesis study was carried out. Female mice received X-ray irradiation (2 x 2 Gray) 2 weeks prior to mating with untreated males. After weaning, half of the descendants were exposed for 6 months to the immunomodulating and tumor-promoting compound cyclosporine A (CsA) by diet, the others remained untreated. The animals were maintained for their entire lifespan, terminal sacrifices were carried out after 28 months. Complete autopsy was performed, and three protocol organs (lung, liver and spleen) were examined histologically, together with any suspicious lesions in other organs. Fertility and the lifetime of the maternal mice were reduced by the X-ray irradiation, and their incidence of lung and liver tumors was increased as compared to non-irradiated mice. The descendants of all groups revealed comparable body weights and mortality rates. The incidence of hematopoietic/lymphoreticular tissue tumors increased in the female hybrids by 6 months of CsA-treatment. A higher incidence of lung and liver tumors in the sham-treated male progeny of irradiated mothers was detected, pointing to a possible germ cell-transmitted alteration initiated by the preconceptual maternal X-ray exposure.