This presentation will be available to view as a discussion poster at the 7th International Conference on the Science of Exposure Assessment - X2012. It will be presented on 04 July 2012 from 09.30 – 11.45 am followed by a chaired discussion of all posters in this session on Chemicals in the Workplace. Appointments with the authors are available to book at https://x2012discussionposters.acuityscheduling.com

1. Sangjun Choi1 , Seongmin Lee2 , Sanghyuk Yim2
1Department of Occupational Health, Catholic University of Daegu, Korea
2Wonjin Institute for Occupational and Environmental Health, Korea
Email (Sangjun Choi): junilane@gmail.com
Abstract
• The purpose of this study is to investigate the relationship between the levels of radon in air and
environmental conditions in the underground, and to develop the management strategies for the
protection of the subway workers.
• The radon levels in air were measured using the US EPA short-term method, and were performed
using the electret passive environment radon monitor (E-PERM).
• The average radon concentrations in the tunnel, the station office, and the platform were 95.1
Bq/㎥, 74.8 Bq/㎥, and 56.3 Bq/㎥, respectively.
• A multiple regression analysis of radon exposure affecting factors showed that the type of tunnel
and the frequency of repair work were found to be a statistically significant predictor of exposure
to radon.
• The estimated average annual effective doses to the technical engineers, subway drivers and the
station office workers from radon were 0.5 mSv/yr, 0.47 mSv/yr and 0.44 mSv/yr, respectively.

2. • Radon is one of the most well known human carcinogens.
• The subway workers working at underground have the
potential of long-term exposure to radon.
• There were radon survey at the platform or station office in
several times. However, radon measurements in
underground tunnels has never been conducted in Korea. < station office >
• The purpose of this study is to evaluate the relationship
between the levels of radon in the station office, platform
and the environmental conditions at the tunnel of subway.
• The radon levels in air were measured using the US EPA
short-term method, and were performed using the electret
passive environment radon monitor (E-PERM).
< Platform>
• A total of 118 stations were selected from Seoul, Busan and
Daegu subways and radon measurements were conducted
at the three points (station office, platform and tunnel) every
station.
• We also investigated environmental conditions such as the
types of bedrocks, the types of tunnel, the amounts of
ground water, the covers of the waterway, the depth of
station, the numbers of natural ventilating opening, the
amounts of ventilation, the frequency of repair works, the
types of roadbeds, and the installation of screen doors. < Tunnel>

3. • The radon concentrations ranged
from 3.4 Bq/㎥ to 961.5 Bq/㎥ at
the 351 measurement points, and
N=351
10% of samples exceeded the
indoor air quality guideline of
Korea, 148 Bq/㎥ (Figure 1).
Figure 1. Cumulative probability of airborne radon concentrations .
• The average radon concentrations
in the tunnel, the station office,
and the platform were 95.1 Bq/㎥,
74.8 Bq/㎥, and 56.3 Bq/㎥,
respectively and there was
statistically significant differences
(p<0.01). (Figure 2)
Figure 2. Comparison of radon concentrations at the station
office, platform and tunnel.

4. • Statistically significant predictors of radon concentrations at the
1. Tunnels : Tunnel type, frequency of repair work and bedrocks
2. Platforms : Radon concentrations at the tunnels, screen door, platform type, bedrocks
3. Station office : Radon concentrations at the platforms, volume of office, depth of platform,
depth of office
Table 1. The summary of multiple regression analyses
Dependent variable Independent variable Unstandardized Standardized t Sig.
Coefficient Coefficients
B Std. Error β
Radon concentrations (Constant) 2.36 0.096 24.536 <0.01
at the tunnels 1)
Tunnel type -0.239 0.05 -0.385 -4.807 <0.01
Frequency of repair work 0.001 0 0.212 2.615 0.01
2)
Bedrocks -0.055 0.022 -0.201 -2.474 0.02
Radon concentrations (Constant) 1.054 0.177 5.947 <0.01
at the platforms Rn at the tunnels 0.429 0.08 0.405 5.373 <0.01
3)
Screen door -0.213 0.06 -0.245 -3.537 <0.01
4)
Platform type 0.124 0.038 0.234 3.279 <0.01
Bedrocks -0.064 0.02 -0.227 -3.161 <0.01
Radon concentrations (Constant) 0.693 0.183 3.791 <0.01
at the station office Rn at the platforms 0.525 0.088 0.483 5.965 <0.01
Volume of office 0.001 0 0.178 2.104 0.04
Depth of platform 0.009 0.003 0.293 3.12 <0.01
Depth of office -0.015 0.006 -0.237 -2.624 0.01
Note. 1) Tunnel type (single =0, double = 1 ), 2) Bedrocks (granite=0, gneiss=1, alluvium=2, andesite=3),
3) Screen door(no=0, yes=1), 4) Platform type(sided platform=0, island platform=1, one way=3)

5. Tunnel Platform Station office
- with Single rail - with Single rail - with deep platform
- with Many cracks - without Screen door - with sided double rail
- surrounded with Granite - surrounded with Granite - surrounded with granite
The estimated average annual effective doses to the technical engineers, subway drivers and the
station office workers from radon were 0.5 mSv/yr, 0.47 mSv/yr and 0.44 mSv/yr, respectively. The
highest value was estimated 4.59 mSv/yr for the station office workers.
This study suggested that radon concentrations at the tunnels should be controlled by repairing
the cracks in order to protect subway workers from radon exposure.