Evaluation of Radon 

Levels at a U.S. 

Government Facility – 

Maine 

Mark M. Methner, PhD, CIH

Health Hazard Evaluation Report

HETA 2011-0031-3167

December 2012

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

Workplace

Safety and Health

 National Institute for Occupational 

Safety and Health
The employer shall post a copy of this report 

for a period of 30 calendar days at or near 

the workplace(s) of affected employees. The 

employer shall take steps to insure that the 

posted determinations are not altered, defaced, 

or covered by other material during such 

period. [37 FR 23640, November 7, 1972, as 

amended at 45 FR 2653, January 14, 1980].
Health Hazard Evaluation Report 2011-0031-3167 Page i

Report Abbreviations................................................................................................ii

Highlights of the NIOSH Health Hazard Evaluation........................iii

Summary ........................................................................................................iv

Introduction ...................................................................................................1

Assessment.....................................................................................................2

Results..............................................................................................................3

Discussion.......................................................................................................4

Conclusions....................................................................................................4

Recommendations.......................................................................................4

References.......................................................................................................4

Contents

Acknowledgments Acknowledgments and Availability of Report...................................9

Appendix Occupational Exposure Limits and Health Effects............................5
Page ii Health Hazard Evaluation Report 2011-0031-3167

Abbreviations

ACGIH® American Conference of Governmental Industrial Hygienists

CFR Code of Federal Regulations

EPA Environmental Protection Agency

HHE Health hazard evaluation

NAICS North American Industry Classification System

NIOSH National Institute for Occupational Safety and Health

OEL Occupational exposure limit

OSHA Occupational Safety and Health Administration

PEL Permissible exposure limit

pCi/L picoCuries per liter of air

REL Recommended exposure limit

STEL Short-term exposure limit

TLV® Threshold limit value

TWA Time-weighted average

WEELTM Workplace environmental exposure level
Health Hazard Evaluation Report 2011-0031-3167 Page iii

The National Institute 

for Occupational Safety 

and Health (NIOSH) 

received a request for a 

health hazard evaluation 

at a government 

building in Maine. 

Union representatives 

of employees from a 

federal agency requested 

assistance in evaluating 

employee exposure to 

naturally-occurring radon 

inside the building. 

Highlights of the

NIOSH Health

Hazard Evaluation

What NIOSH Did

● We measured radon levels from January 2012 to May 2012.

● We measured radon levels inside and outside the building. 

What NIOSH Found

● Radon concentrations outdoors and in the occupied work 

area were below OSHA and EPA exposure limits.

● Radon concentrations in the basement were higher than in 

the work area or outdoors. Employees usually do not work 

in the basement. 

What Managers Can Do

● Ensure employees minimize the time spent in the basement.

● Consider installing a ventilation system in the basement 

to remove radon if this space is ever used as an occupied 

work area.

What Employees Can Do

● Minimize the time spent in the basement. 
Page iv Health Hazard Evaluation Report 2011-0031-3167

Summary

 In December 2010, NIOSH received an HHE request from the 

union representing employees at a government facility in Maine. 

NIOSH was asked to evaluate employees’ exposure to radon gas 

during normal work activities at the facility (e.g., inspecting vehicles 

and materials, collecting duties, and confiscating contraband). 

The primary employee health concern at this facility was exposure 

to naturally-occurring radon gas. We evaluated the facility on 

January 31–February 2, 2012. We observed work practices and 

measured radon levels in the occupied work areas and the typically 

unoccupied basement. The radon measurements were recorded at 

10-minute intervals over approximately 48 hours. We also placed 

long-term Radtrak® radon detectors in the work area, basement, 

and outdoors; these detectors were collected on May 30, 2012, and 

analyzed by the manufacturer.

Radon levels averaged 0.8 ± 1.7 pCi/L in the first floor work area 

and higher (3.8 ± 3.9 pCi/L) in the basement on February 1-2, 2012. 

The radon levels did not fluctuate substantially during the day. No 

detectable levels of radon were found in the outdoor inspection lane 

over a 4-month sampling period. Over 4 months, radon levels in the 

first floor work area averaged 0.6 pCi/L, while the basement average 

was 7.5 pCi/L. All of these radon levels are well below the OSHA 

PEL of 100 pCi/L. The radon levels in the occupied first floor were 

also below the EPA residential guideline of 4 pCi/L, but the levels in 

the unoccupied basement were above the EPA guideline. Following 

the principle of keeping exposures to ionizing radiation as low as 

possible, we recommend that employees minimize the time they 

spend in the basement. 

A NIOSH investigator 

evaluated employee 

exposures to radon. We 

found that radon levels in 

the first floor work area 

were well below the OSHA 

PEL of 100 pCi/L, and also 

below the much lower EPA 

residential guideline of 

4 pCi/L. However, radon 

levels in the basement 

were higher than on the 

first floor, but the basement 

was typically unoccupied. 

We recommend that 

employees minimize the 

time they spend in the 

basement to keep exposure 

to radon as low as 

practical. If the basement is 

ever used as a work space, 

installing a basement 

radon mitigation system 

should be considered.

Keywords: NAICS 921130 (Public finance activities), radiation, radon, 

radon progeny, exposure, Radtrak®
Health Hazard Evaluation Report 2011-0031-3167 Page 1

Introduction

In December 2010, NIOSH received an HHE request from a 

union representative on behalf of employees at a government 

facility in Maine. NIOSH was asked to evaluate levels of radon in 

the workplace. The primary health concern at this facility involved 

inhalation exposure to naturally-occurring radon gas. We evaluated 

the facility on January 31, 2012–February 2, 2012. We observed work 

practices and measured radon levels in the work area and basement. 

The radon measurements were recorded at 10-minute intervals over 

approximately 48 hours. We placed long-term Radtrak® radon 

detectors in the work area, basement, and outdoors; these detectors 

were collected on May 30, 2012, and analyzed by the manufacturer. 

This report contains our findings and recommendations from our 

evaluation of radon gas at the facility.

The brick and wood facility was constructed in 1931 and was leased 

from the U.S. government. It had two floors above grade and a 

poured concrete basement. Heat was provided by an oil-fired boiler 

that supplied hot water to perimeter baseboard radiators. The 

building did not have central air-conditioning, but several rooms 

had window-mounted units. Employees could also open windows. 

The basement was used primarily for storage, but also housed 

supplies, electronic equipment, and the oil-fired boiler. The second 

floor was used exclusively for storage. 

The first floor was divided into two offices and a work area where 

employees monitored vehicles and people entering the United 

States from Canada 24 hours per day. Employees spent about 

80% of their 8-hour work shift in the first floor offices, and the 

remainder of their shift was spent outdoors inspecting vehicles. 

At the time of our evaluation 29 employees worked rotating shifts 

between this facility and others along the border. On average, four 

to six employees worked 8-hour work shifts at this facility.

Radon and its Health Effects 

Radon is a colorless, tasteless radioactive gas that is formed via 

the radioactive decay of radium. Radium is common in many 

soils and rocks, though its concentration can vary widely. Because 

radon is a gas, it can leave the soil or rock where it formed and 

enter the surrounding air. Therefore, radon levels can build up 

when ventilation rates are low or when a large amount of radium 

is present.
Page 2 Health Hazard Evaluation Report 2011-0031-3167

Introduction

 (continued) Cancer is the major effect of concern from radium and radon 

radionuclides [ATSDR 1990; DOE 1995]. Inhalation is the 

primary route of radon exposure. Exposure to radon increases a 

person’s risk for lung cancer, and smokers exposed to radon are at 

greater risk for lung cancer (approximately 10 to 20 times) than are 

similarly exposed nonsmokers [ATSDR 1990].

Across the United States, background concentrations of radon 

in outdoor air range from 0.003 to 2.6 pCi/L and are higher in 

areas with uranium and thorium deposits or granite formations 

[DOE 1995]. During the winter of 1988–1989, the EPA used 

charcoal canisters in a 2 to 7 day measurement survey for radon 

in 839 homes across all 16 counties in Maine. The EPA found 

that in the county where this facility is located, along with four 

other counties in central and southern Maine, the average 

radon concentrations exceeded 4 pCi/L [EPA 1993]. The EPA 

recommends taking corrective measures when in-home radon 

levels exceed 4 pCi/L. However, the recommendations and 

action levels for indoor radon provided by the EPA are neither 

enforceable nor applicable for a workplace environment. For 

occupational settings, the OSHA PEL is 100 pCi/L for a 40-

hour exposure in any workweek of 7 consecutive days. See the 

Appendix for information on exposure limits.

Short-term Real-time Measurements

We measured radon in the first floor work area and basement 

areas using a PRISM Model 597-PX3 monitor (alphaNUCLEAR®, 

Saskatoon, Saskatchewan, Canada). The portable monitor was set 

to data-log radon levels every 10 minutes over approximately 48 

hours. The limit of detection of this instrument is 0.1 pCi/L.

Long-term Passive Measurements

We used Radtrak detectors (Landauer, Inc., Glenwood, Illinois) 

to passively measure radon levels over a 4-month period. These 

detectors contain a polymer film inside a perforated metal 

container. Radon diffuses into the container and decays into 

electrically charged daughter products, which stick to the polymer 

film and are subsequently counted by the manufacturer. The limit 

of detection is 30 pCi/L/day (the equivalent of 30 days at 1 pCi/L, 

or 15 days at 2 pCi/L, etc). Our detectors were exposed for 121 

Assessment
Health Hazard Evaluation Report 2011-0031-3167 Page 3

days (January 31, 2012–May 30, 2012), resulting in a minimum 

detectable concentration of 0.3 pCi/L. Detectors were placed (in 

triplicate) approximately 5 feet above the floor in the basement, in 

the first floor work area, and outdoors in the vehicle inspection 

lanes. We also collected four field blanks.

Assessment

 (continued)

Results Radon concentrations averaged 0.8 ± 1.7 pCi/L in the work area, 

on the basis of 273 measurements across 48 hours. Average radon 

concentrations in the basement were higher, 3.8 ± 3.9 pCi/L on 

the basis of 290 measurements. Radon levels did not fluctuate 

substantially throughout the day.

Table 1 shows the results from the passive monitoring across the 

121-day period. Results for the outdoor detectors were below the 

limit of detection (0.3 pCi/L), while levels in the work area were 

slightly higher (0.6 pCi/L). Results for the detectors placed in the 

basement averaged 7.5 pCi/L over the 121-day sampling period.

Table 1. Radon levels measured between January 31, 2012 and 

May 30, 2012

Sample Location Average Radon Concentration (pCi/L)

Outdoors/inspection lane

ND*

ND*

ND*

First floor work area

0.6

0.6

0.6

Basement

7.2

7.5

7.8

*ND – Not detected; the levels were below the minimum detectable 

concentration of 0.3 pCi/L. All field blanks were ND.
Page 4 Health Hazard Evaluation Report 2011-0031-3167

D
Health Hazard Evaluation Report 2011-0031-3167 Page 5

Appendix: Occupational Exposure Limits and Health Effects

In evaluating the hazards posed by workplace exposures, NIOSH investigators use both mandatory (legally 

enforceable) and recommended OELs for chemical, physical, and biological agents as a guide for making 

recommendations. OELs have been developed by federal agencies and safety and health organizations to 

prevent the occurrence of adverse health effects from workplace exposures. Generally, OELs suggest levels 

of exposure that most employees may be exposed to for up to 10 hours per day, 40 hours per week, for a 

working lifetime, without experiencing adverse health effects. However, not all employees will be protected 

from adverse health effects even if their exposures are maintained below these levels. A small percentage 

may experience adverse health effects because of individual susceptibility, a preexisting medical condition, 

and/or a hypersensitivity (allergy). In addition, some hazardous substances may act in combination with 

other workplace exposures, the general environment, or with medications or personal habits of the 

employee to produce adverse health effects even if the occupational exposures are controlled at the level set 

by the exposure limit. Also, some substances can be absorbed by direct contact with the skin and mucous 

membranes in addition to being inhaled, which contributes to the individual’s overall exposure. 

Most OELs are expressed as a TWA exposure. A TWA refers to the average exposure during a normal 8- 

to 10-hour workday. Some chemical substances and physical agents have recommended STEL or ceiling 

values where adverse health effects are caused by exposures over a short period. Unless otherwise noted, 

the STEL is a 15-minute TWA exposure that should not be exceeded at any time during a workday, and 

the ceiling limit is an exposure that should not be exceeded at any time.

In the United States, OELs have been established by federal agencies, professional organizations, state 

and local governments, and other entities. Some OELs are legally enforceable limits, while others are 

recommendations. The U.S. Department of Labor OSHA PELs (29 CFR 1910 [general industry]; 29 

CFR 1926 [construction industry]; and 29 CFR 1917 [maritime industry]) are legal limits enforceable 

in workplaces covered under the Occupational Safety and Health Act of 1970. NIOSH RELs are 

recommendations based on a critical review of the scientific and technical information available on a 

given hazard and the adequacy of methods to identify and control the hazard. NIOSH RELs can be 

found in the NIOSH Pocket Guide to Chemical Hazards [NIOSH 2010]. NIOSH also recommends different 

types of risk management practices (e.g., engineering controls, safe work practices, employee education/

training, personal protective equipment, and exposure and medical monitoring) to minimize the risk of 

exposure and adverse health effects from these hazards. Other OELs that are commonly used and cited 

in the United States include the TLVs recommended by ACGIH, a professional organization, and the 

WEELs recommended by the American Industrial Hygiene Association, another professional organization. 

The TLVs and WEELs are developed by committee members of these associations from a review of the 

published, peer-reviewed literature. They are not consensus standards. ACGIH TLVs are considered 

voluntary exposure guidelines for use by industrial hygienists and others trained in this discipline “to assist 

in the control of health hazards” [ACGIH 2012]. WEELs have been established for some chemicals “when 

no other legal or authoritative limits exist” [AIHA 2012].

Outside the United States, OELs have been established by various agencies and organizations and 

include both legal and recommended limits. The Institut für Arbeitsschutz der Deutschen Gesetzlichen 

Unfallversicherung (IFA, Institute for Occupational Safety and Health of the German Social Accident 
Page 6 Health Hazard Evaluation Report 2011-0031-3167

Appendix: Occupational Exposure Limits and Health Effects

 (continued)

Insurance) maintains a database of international OELs from European Union member states, Canada 

(Québec), Japan, Switzerland, and the United States. The database, available at http://www.dguv.de/ifa/

en/gestis/limit_values/index.jsp, contains international limits for over 1,500 hazardous substances and is 

updated periodically. 

Employers should understand that not all hazardous chemicals have specific OSHA PELs, and for some 

agents the legally enforceable and recommended limits may not reflect current health-based information. 

However, an employer is still required by OSHA to protect its employees from hazards even in the absence 

of a specific OSHA PEL. OSHA requires an employer to furnish employees a place of employment free 

from recognized hazards that cause or are likely to cause death or serious physical harm [Occupational 

Safety and Health Act of 1970 (Public Law 91–596, sec. 5(a)(1))]. Thus, NIOSH investigators encourage 

employers to make use of other OELs when making risk assessments and risk management decisions to 

best protect the health of their employees. NIOSH investigators also encourage the use of the traditional 

hierarchy of controls approach to eliminate or minimize identified workplace hazards. This includes, in 

order of preference, the use of (1) substitution or elimination of the hazardous agent, (2) engineering 

controls (e.g., local exhaust ventilation, process enclosure, dilution ventilation), (3) administrative controls 

(e.g., limiting time of exposure, employee training, work practice changes, medical surveillance), and (4) 

personal protective equipment (e.g., respiratory protection, gloves, eye protection, hearing protection). 

Control banding, a qualitative risk assessment and risk management tool, is a complementary approach 

to protecting employee health that focuses resources on exposure controls by describing how a risk 

needs to be managed. Information on control banding is available at http://www.cdc.gov/niosh/topics/

ctrlbanding/. This approach can be applied in situations where OELs have not been established or can be 

used to supplement the OELs, when available.

References

ACGIH [2012]. 2012 TLVs® and BEIs®: threshold limit values for chemical substances and physical 

agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental 

Industrial Hygienists.

AIHA [2012]. AIHA 2012 Emergency response planning guidelines (ERPG) & workplace environmental 

exposure levels (WEEL) handbook. Fairfax, VA: American Industrial Hygiene Association.

CFR. Code of Federal Regulations. Washington, DC: U.S. Government Printing Office, Office of the 

Federal Register.

NIOSH [2010]. NIOSH pocket guide to chemical hazards. Cincinnati, OH: U.S. Department of Health 

and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational 

Safety and Health, DHHS (NIOSH) Publication No. 2010-168c. [http://www.cdc.gov/niosh/npg/]. Date 

accessed: December 2012.
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Health Hazard Evaluation Report 2011-0031-3167 Page 9

The Hazard Evaluations and Technical Assistance Branch 

(HETAB) of the National Institute for Occupational Safety and 

Health (NIOSH) conducts field investigations of possible health 

hazards in the workplace. These investigations are conducted 

under the authority of Section 20(a)(6) of the Occupational Safety 

and Health Act of 1970, 29 U.S.C. 669(a)(6) which authorizes 

the Secretary of Health and Human Services, following a written 

request from any employer or authorized representative of 

employees, to determine whether any substance normally found 

in the place of employment has potentially toxic effects in such 

concentrations as used or found. HETAB also provides, upon 

request, technical and consultative assistance to federal, state, and 

local agencies; labor; industry; and other groups or individuals to 

control occupational health hazards and to prevent related trauma 

and disease.

Mention of any company or product does not constitute 

endorsement by NIOSH. In addition, citations to websites 

external to NIOSH do not constitute NIOSH endorsement of 

the sponsoring organizations or their programs or products. 

Furthermore, NIOSH is not responsible for the content of these 

websites. All Web addresses referenced in this document were 

accessible as of the publication date.

This report was prepared by Mark M. Methner of HETAB, 

Division of Surveillance, Hazard Evaluations and Field Studies. 

Industrial hygiene equipment and logistical support was provided 

by Donald Booher and Karl Feldmann. Analytical support was 

provided by Landauer, Glenwood, Illinois. Health communication 

assistance was provided by Stefanie Brown. Editorial assistance was 

provided by Ellen Galloway. Desktop publishing was performed by 

Mary Winfree. 

Copies of this report have been sent to union and management 

representatives at the facility, the state health department, and 

the Occupational Safety and Health Administration Regional 

Office. This report is not copyrighted and may be freely 

reproduced. The report may be viewed and printed at http://

www.cdc.gov/niosh/hhe/. Copies may be purchased from the 

National Technical Information Service at 5825 Port Royal Road, 

Springfield, Virginia 22161.

Acknowledgments and

Availability of Report
Below is a recommended citation for this report:

NIOSH [2012]. Health hazard evaluation report: evaluation of radon exposure at 

a government facility – Maine. By Methner M. Cincinnati, OH: U.S. Department of 

Health and Human Services, Centers for Disease Control and Prevention, National 

Institute for Occupational Safety and Health, NIOSH HETA No. 2011-0031-3167.

To receive NIOSH documents or information about 

occupational safety and health topics, contact NIOSH at:

1-800-CDC-INFO (1-800-232-4636)

TTY: 1-888-232-6348

E-mail: cdcinfo@cdc.gov

or visit the NIOSH web site at: www.cdc.gov/niosh.

For a monthly update on news at NIOSH, subscribe to 

NIOSH eNews by visiting www.cdc.gov/niosh/eNews.

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