Environmental Radiation Monitoring

Frequently Asked Questions about Environmental Radiation Monitoring

A. Ambient Radiation Monitoring Programme in Singapore
B. Background Radiation Level in Singapore
C. Interpretation of Background Radiation Levels in Singapore

A. Ambient Radiation Monitoring Programme in Singapore

1. How does NEA monitor the ambient radiation levels in Singapore?

NEA operates a network of forty (40) air and water radiation monitoring stations. These stations deployed across Singapore are equipped with automatic continuous analysers and measure a range of radiological parameters, such as gamma dose rate and radionuclide concentrations in the environment. The monitoring equipment are passive sensors that do not emit radiation and are therefore safe to be deployed in population centres.


2. Where are the locations of NEA's radiation monitoring stations?

NEA’s radiation monitoring stations are placed across Singapore, with at least five monitoring stations in each region.


3. How did NEA decide on the location of the monitoring stations?

The locations of the monitoring station were selected to provide optimal monitoring coverage across the whole of Singapore. 

B.  Background Radiation Levels in Singapore

1. What is Singapore background radiation level?

Singapore’s background radiation level is about 0.1 micro-Sievert per hour. This is comparable to the background radiation levels in other cities countries such as Hong Kong SAR, Republic of Korea and Germany¹. As a comparison, typical amount of radiation exposure for flight personnel on a commercial airplane is about 2 micro-Sievert per hour².


2. What is gamma dose rate and how is it measured?

Gamma radiation can easily penetrate the human body and is absorbed readily by the various organs.

The background radiation level is measured in terms of gamma dose rate, which is the dose of gamma radiation delivered per unit of time. Gamma dose rate is often used as an indicator for early detection of any abnormalities in the radioactivity in environment and is the common measurement used by countries during a radiological incident.


3. What is the unit of measurement for gamma dose rate?

Gamma dose rate is reported in micro-sievert (1/1,000,000^th of a sievert) per hour (i.e. µSv/h). 


4. How are the five regions (North, South, East, West and Central) determined and which region should I look at?

The five regions used for reporting ambient radiation level in Singapore are based on town centres/area. A general guide of the town centres/areas within each of the give regions is indicated on the map below. If your location is not listed, please use the region closest to you. 

The map above is intended for illustrative purpose only.

5. How is the gamma dose rate computed?

The regional gamma dose rate is computed based on 24-hr average of gamma dose rate readings obtained from all the monitoring stations in a particular region. The reading is updated once a day and is based on readings collected from previous day 9am to current day 9am. 

6. Why is the radiation level updated only once a day? 

Based on observation from past years of monitoring, other than temporal variations caused by meteorological conditions such as rainfall and wind, there is little fluctuation in the background radiation levels. Hence a daily update would suffice.

Notwithstanding, NEA constantly reviews our reporting regime and will consider more frequent update in the future. 


C. Interpretation of Background Radiation Level in Singapore

1. How do I interpret the gamma dose rate reading and what level is considered safe? 

There is no international guideline on the safe limit of background radiation level to a person. However, here are some guides to help you. 

• Singapore’s background radiation level is about 0.1 micro-Sievert per hour.
• According to International Commission on Radiological Protection (ICRP), the dose limit for a member of the public (non-occupational radiation worker) is 1 milli-Sievert (or 0.001 Sievert) per year. This limit applies to doses received over and above the normal local natural background radiation. 

2. What does the status ‘Normal’ mean? 

A status of ‘Normal’ indicates that the ambient radiation level is within the normal fluctuation range in Singapore.


3. What happens when readings are above 'Normal'? 

In the event the readings are above “Normal”, an investigation will be carried out to look into the cause of the elevated readings. Public will be advised of any protective measures that need to be taken, if necessary. The IAEA and ICRP stipulate that no protective action is required for dose levels less than 1 micro-Sievert per hour.


4. What do the gamma dose rate readings vary across different regions in Singapore? 

Background radiation levels vary from place to place and over time, depending on the amount of naturally occurring radioactive materials (NORMS) present in soil, rock, buildings, water and air. Other factors that may affect the radiation levels include weather conditions, cosmic radiation, as well as the presence of anthropogenic materials present.

^1.Ambient gamma radiation dose rate in Hong Kong SAR, Republic of Korea and Germany can be obtained from Hong Kong Observatory website at https://www.hko.gov.hk/en/radiation/monitoring/index.html, Korea Institute of Nuclear Safety at https://iernet.kins.re.kr/index.asp?ke_flag=E and Germany Bundesamt für Strahlenschutz (BfS) at https://odlinfo.bfs.de/ODL/EN/home/home_node.html 

^2.Source from Feng YJ, Chen WR, Sun TP, Duan SY, Jia BS, Zhang HL. Estimated cosmic radiation doses for flight personnel. Space Med Eng 15(4):25-269; 2002.