Measurement of personal radio frequency exposure in Japan: The Hokkaido Study on the Environment and Children's health.

The opportunities for exposure to radiofrequency electromagnetic fields (RF-EMF) among children are increasing. Children's exposure to RF-EMF in Japan was recorded using a personal exposure meter (ExpoM-RF), and factors associated with the exposure examined. A total of 101 children, aged 10-15 years old, participated in the prospective birth cohort "Hokkaido study". RF-EMF data were recorded in the 700 MHz-5.8 GHz frequency range for 3 days. The recorded data were summarized into six groups of frequency bands: downlink from mobile phone base stations (DL), uplink from mobile phones to a base station (UL), Wireless Local Area Network (LAN), terrestrial digital TV broadcasting (digital TV), 2.5 GHz and 3.5 GHz Time Division Duplex (TDD), 1.9 GHz TDD, and total (the summation of power density in all measured frequency bands). A questionnaire was used to document the internet environment (at home) and mobile phone usage. Personal RF-EMF exposure in Japanese children was lower than that reported in studies in Europe. The DL signals from mobile phone base stations were the most significant contributors to total exposure, while Wireless LAN and digital TV were only higher at home. The urban residence was consistently associated with increases in the four groups of frequency bands (DL, UL, digital TV, and TDD). TDD level has several associations with mobile phone usage (calls using mobile phones, video viewing, text message service, and online game). The association between inattention/hyperactivity subscale of the Strengths and Difficulties Questionnaire (SDQ) and higher Wireless LAN exposure at nighttime was also noted. Further studies with additional data will shed light on factors involved in RF-EMF exposure among Japanese children.

Radiofrequency Exposure Levels from Mobile Phone Base Stations in Outdoor Environments and an Underground Shopping Mall in Japan.

Recent progress in wireless technologies has made human exposure to electromagnetic fields (EMFs) increasingly complex. The situation can increase public concerns related to possible health effects due to EMF exposure. Monitoring EMF exposure levels and characterizing them are indispensable for risk communications of human exposure to EMFs. From this background, a project on the acquisition, accumulation, and applications of EMF exposure monitoring data in Japan was started in 2019. One of the objectives of this project is to obtain a comprehensive picture of EMF exposure in actual daily lives. In 2019 and 2020, we measured the electric field (E-field) strength from mainly mobile phone base stations in the same areas as those in measurements conducted in 2006 and 2007 by the Ministry of Internal Affairs and Communications (MIC), Japan, and compared the data to investigate the time-course of the EMF environment. The number of measured points was 100 (10 × 10 grids) in an area of 1 km × 1 km in two urban and two suburban areas, and that in an underground shopping mall was 158. This large-scale study is the first in Japan. As a result, we found that the measured E-field strengths tended to be higher in 2019 and 2020 than those in 2006 and 2007, especially in the mall. However, the median ratios to the Japanese radio wave protection guideline values for urban areas and malls are lower than -40 dB.

Production of extracellular bifidogenic growth stimulator (BGS) from Propionibacterium shermanii using a bioreactor system with a microfiltration module and an on-line controller for lactic acid concentration.

Production of a bifidogenic growth stimulator (BGS) by Propionibacterium freudenreichii subsp. shermanii (Propionibacterium shermanii) using lactic acid as a carbon source was investigated using different cultivation methods. When a continuous bioreactor system with a filtration device was used at a dilution rate of 0.075 h(-1), the average BGS concentration was 2.4 mg/l, which corresponds to a BGS productivity per cultivation time of 1.8 x 10(-1) mg x l(-1) x h(-1). The BGS productivity per cultivation time in continuous cultivation with filtration was 1.9-fold that (9.4 x 10(-2) mg x l(-1).h(-1)) in a conventional batch cultivation. In fed-batch cultivation with feed-back control using an on-line lactic acid controller with a lactic acid biosensor, it was possible to prevent substrate inhibition by maintaining the lactic acid concentration in culture broth low at 3.3 g/l, and an enhanced BGS production (31 mg/l) was successfully attained. The BGS productivity per cultivation time (2.1x10(-1) mg x l(-1) x h(-1)) in the fed-batch cultivation with feed-back control was 2.2-fold that in the conventional batch cultivation. A new bioreactor system was developed by coupling a continuous bioreactor system with a filtration device to an on-line lactic acid controller. Using the new bioreactor system, we produced BGS continuously at a high level of 47 mg/l. The BGS productivities per cultivation time (3.5 mg.l(-1) x h(-1)) and the total volume of medium used (1.7 x 10(-1) mg x l(-1) x h(-1)) obtained in the new bioreactor system were 37-fold and 2.1-fold those in the conventional batch cultivation, respectively. These results described above clearly demonstrate the positive effects of both the continuous filtration for removal of metabolites (propionic and acetic acids) inhibitory to cell growth and feed-back control of lactic acid concentration in the culture broth on BGS production by P. shermanii. This paper is the first report on BGS production by the propionic acid bacterium using lactic acid as a carbon source.