Video display terminals and radon.
Recent reports indicate that video display terminals (VDTs) can collect radon progeny from the air. This occurs especially when they are turned off and may have negative electric fields which attract positively charged radioactive dust. We have studied this phenomenon in detail and evaluated various techniques for removing the gettered radioactivity while the video display terminal is both off and on. We have evaluated what happens when the video display terminal is switched, thereby reversing the electric field near the screen. We have also studied possible inhalation effects by a video display terminal operator during field reversal and find that although some radioactivity may be released during the cycle, room air currents redistribute it into the room with no detectable levels being inhaled by users.
Alterações cromossômicas causadas pela radiação dos monitores de vídeo de computadores
OBJETIVO: Em decorrencia dos questionamentos sobre o efeito deleterio das radiacoes emitidas pelo campo eletromagnetico (CEM) dos tipos ELF (extremely low frequency) e VLF (very low frequency) transmitidas pelos monitores de video dos computadores (CRT), foi avaliada a frequencia de anomalias cromossomicas estruturais e a cinetica do ciclo celular em individuos expostos por seu trabalho a radiacao dos CRT. METODOS: A pesquisa de aberracoes cromossomicas foi realizada em 2.000 metafases de primeira divisao celular obtidas de culturas de 48h de linfocitos de sangue venoso periferico de dez individuos expostos ao CRT (grupo E) e de dez controles (grupo C). A cinetica do ciclo celular foi pesquisada pelos indices mitotico (IM) e de proliferacao celular (IPC). RESULTADOS: A analise estatistica evidenciou frequencias significativamente maiores de metafases com anomalias cromossomicas (E=5,9%; C=3,7%) e anomalias/celula (E=0,066±0,026; C=0,040±0,026) nos individuos expostos aos CRTs. As alteracoes citogeneticas mais comuns foram as quebras cromatidicas, com frequencia de 0,034±0,016 no grupo E e de 0,016±0,015 no grupo C. As frequencias de IM e IPC nao apresentaram diferencas significantes entre os grupos avaliados. CONCLUSOES: Os resultados sugerem um efeito genotoxico do CEM emitido pelos CRTs devido a frequencia mais elevada de quebras cromatidicas, enfatizando a necessidade de haver um numero maior de estudos com diferentes tecnicas que vise a investigar a acao do CEM sobre o material genetico.
Size distribution of radon daughter particles in uranium mine atmospheres.
The size distribution of radon daughters was measured in several uranium mines using four compact diffusion batteries and a round jet cascade impactor. Simultaneously, measurements were made of uncombined fractions of radon daughters, radon concentration, working level and particle concentration. The size distributions found for radon daughters were log normal. The activity median diameters ranged from 0.09 mum to 0.3 mum with a mean value of 0.17 mum. Geometric standard deviations were in the range from 1.3 to 4 with a mean value of 2.7. Uncombined fractions expressed in accordance with the ICRP definition ranged from 0.004 to 0.16 with a mean value of 0.04. The radon daughter sizes in these mines are greater than the sizes assumed by various authors in calculating respiratory tract dose. The disparity may reflect the widening use of diesel-powered equipment in large uranium mines.