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Radon Day Care Survey in North Dakota 1991-1992

During the second and third years of a three year grant from the EPA, the Department began testing for radon in over 2,000 licensed day care facilities. All day cares in the State were invited to participate in the survey. The day care facilities are licensed by the North Dakota Department of Human Services.

During January 1991, the Department mailed 2,019 application packets to day care operators. Of the 2,019 day care facilities solicited, 545 facilities responded over the two-year period. Radon reports were not received from any day care facilities in seven counties. Tables 7 and 8 represent the city and county statistics derived from the day care radon survey.

Sampling

The Department followed EPA guidance for sampling protocol. This resulted in a significant number of parameters as shown in Table 7. Every third facility was sent a duplicate and every seventh facility received a field blank.

  1. At least one detector was placed on each level of the house.
  2. After locating one detector on each level, the locations were prioritized (based upon room occupancy).

    Highest Priority Rooms: living room, recreation room, dining room, and family room.

    Lower Priority Rooms: bedroom, sleeping room, TV room, toy room, kitchen, entry, etc.

    Not tested: cloak room, bathroom, pantry, furnace room, etc.

The Department followed EPA guidance to formulate its quality assurance plan and used the National Database format for recording collected data.

The precision was determined by locating two samplers next to each other.

Precision 1991 - Coefficient of variation 16.7% / Standard deviation 29.6.

Precision 1992 - Coefficient of variation 9.5% / Standard deviation 11.4.

The coefficient of variation is defined as the product of 100 and the standard deviation divided by the average of the two duplicate samples.

Based on these tests, the day care radon measurements appear to be relatively precise.

The accuracy was determined from a series of samples that were exposed in radon chambers in laboratories at the Office of Radiation Programs - National Air and Radiation Environmental Laboratory, Las Vegas, Nevada (1991) facility or Montgomery, Alabama (1992) facility. A total of 24 sampling vials were sent to Las Vegas and 181 sampling vials to Montgomery. A summary of the accuracy tests is given below:

DAY CARE ACCURACY STATISTICS BY PARAMETER


                         KNOWN              % OF KNOWN            STANDARD      
     YEAR                pCi/l            CONCENTRATION          DEVIATION      

     1991                 5.9                  72.7                 4.73          

     1991                11.9                  93.5                13.44          

     1992                 5.4                 110.7                12.37          

     1992                12.8                 110.5                 4.86          



The day care radon measurements are accurate except for the 5.9 pCi/l concentration (72.7%) in 1991. The high standard deviations (13.44 and 12.37) are indicative of large variations which are a concern to the Department.

PARAMETERS - Description of Statistics by Selected Parameter

The results of the parameters measured for day care facilities are found in Table 7.

Mobile Home
Mobile homes (2.8% of the samples) had an arithmetic mean of 3.0 pCi/l and 15.0% had a concentration greater than 4 pCi/l.

Type of Building
The single family type of building (85.1% of samples) has the highest arithmetic mean and the greatest percentage of samples greater than 4 pCi/l.

Type of Basement
The buildings with basements type, 77.8% of buildings sampled, exhibited the largest arithmetic mean and percentages greater than 4 or 20 pCi/l.

Test Location Floor
The basement sample location, which represented 31.5% of the samples, averaged 51.2% greater than 4 pCi/l. They had the highest percentage greater than 20 pCi/l, 3.6%, and had an average arithmetic mean of 6.1 pCi/l.

SUMMARY

Most homes were closed, not using their fireplace, did not have an air conditioner on and did not have a central air conditioning system.

The database contained 1,686 samples with an arithmetic mean concentration of 5.26 pCi/l. The standard deviation was 6.89.

The percentages of samples greater than 4 or 20 pCi/l were 41.4% and 3.0%, respectively.

FIGURE 3 - Log Normal Distribution

Daycare Graph

Number of Samples: 1686

The curve obtained from the Day Care Survey is LOGNORMAL (see Figure 3). The above graph is combined with the lognormal graphs for the other surveys and may be found in Figure 8.

TABLE 7

DAY CARE SURVEY STATISTICS SUMMARY

                                                                     PERCENTAGE                       
                                                                         OF                                   
                            NUMBER                  ARITHMETIC         SAMPLE                        
                              OF        ARITHMETIC   STANDARD       GREATER THAN                          
PARAMETERS                  SAMPLES        MEAN      DEVIATION  4 pCi/l        20 pCi/l                                 
                                                 

MOBILE HOME                                                                                         
  Yes                          47           3.8         5.0      19.1              2.1              
  No                         1639           5.3         6.9      42.0              3.0              

TYPE OF BUILDING                                                                                    
  Single Family              1434           5.6         7.3      45.3              3.1              
  Multi Family                 82           3.0         1.7      23.2              0.0              
  Business                     56           3.8         5.7      19.6              7.1              
  School                       41           3.0         4.4      17.1              2.4              
  Other                        73           2.5         1.9      16.4              0.0              

BASEMENT CRAWL SPACE                                                                                
 SLAB-ON-GRADE                                                                                        
  Basement                   1311           5.5         6.7      45.2              3.1              
  Crawl Space                  62           4.7         7.4      22.6              8.1              
  Slab-on-Grade               194           4.7         9.3      29.9              2.1              
  Other                       119           3.4         3.4      28.6              0.8              

TEST LOCATION FLOOR                                                                                 
  Basement                    531           6.9         8.1      57.1              4.5              
  First Floor                1039           4.6         6.4      35.4              2.4              
  Second Floor & Above        116           3.4         3.3      23.3              0.9              

HEAT DISTRIBUTION TYPE                                                                              
  Hot Air                    1216           5.4         6.8      43.4              3.2              
  Hot Water                   239           3.6         4.1      28.0              1.3              
  Radiant                      71           4.2         3.3      42.3              0.0              
  Individual Room Units       116           7.6        11.8      48.3              6.0              
  Other                        42           4.8         5.7      35.7              2.4              

ROOM TYPE                                                                                           
  Bedroom                     504           5.1         6.6      41.5              2.0              
  Family Room                 213           5.6         6.2      46.5              1.9              
  Living Room                 352           4.6         7.2      35.2              1.7              
  Unfinished Basement          58           6.9         6.2      63.8              6.9              
  Office                        4           5.7         4.5      50.0              0.0              
  Classroom                    84           3.3         4.1      19.0              2.4              
  Other                       196           5.3         7.0      39.3              4.1              
  Finished Basement            25           7.1         4.7      68.0              0.0              
  Kitchen                      51           5.4         8.8      33.3              3.9              
  Recreation Room              42           7.0         6.4      66.7              7.1              
  Dining Room                  42           5.3         7.6      33.3              4.8              
  Play Room                    66           7.0         7.6      54.5              6.1              
  TV Room                       6           4.8         3.3      50.0              0.0              
  Sleeping Room                29           6.4                  48.3             13.8              
  Nursery                      13           8.0         7.3      30.8              7.7              
                                                       15.2                                         

GEOLOGICAL REGION                                                                                   
  1                           191           5.2         8.3      33.5              3.7              
  2                           606           7.0         8.9      54.3              5.1              
  3                           889           4.1         4.3      34.3              1.3              

BASEMENT SUMP                                                                                       
  Yes                         440           7.5         9.4      54.3              7.0              
  No                         1246           4.5         5.6      36.8              1.5              

TYPE OF FACILITY                                                                                    
  Center                       89           3.8         5.3      19.1              5.6              
  Family                     1084           5.0         5.5      42.1              2.6              
  Group                       477           6.4         9.6      44.7              3.6              
  Half-day                     11           3.7         2.3      45.5              0.0              
  Multiple License             17           3.4         2.8      35.3              0.0              
  Public Approval               6           1.1         0.8       0.0              0.0              


CLOSED HOUSE                                                                                        
  Yes                        1146           5.3         7.0      41.1              3.1              
  No                          540           5.2         6.7      42.0              2.8              

FIREPLACE IN USE                                                                                    
  Yes                          71           4.9         5.2      45.1              1.4              
  No                         1615           5.3         7.0      41.2              3.0              

AIR CONDITIONER IN USE                                                                              
  Yes                           9          10.2         8.8      44.4             11.1              
  No                         1677           5.2         6.9      41.4              2.9              

CENTRAL AIR SYSTEM                                                                                  
  Yes                         648           6.4         8.7      48.0              4.9              
  No                         1038           4.5         5.4      37.3              1.7              


TABLE8

DAY CARE SURVEY STATISTICS BY COUNTY


                                                          PERCENTAGE        PERCENTAGE        
                 NUMBER                     ARITHMETIC     OF SAMPLES        OF SAMPLES        
                   OF        ARITHMETIC     STANDARD      GREATER THAN      GREATER THAN      
COUNTY          SAMPLES        MEAN         DEVIATION        4 pCi/l          20 pCi/l         

Adams              6           13.3            7.4            83.3              16.7          

Barnes            33            8.8            7.9            75.8              15.2          

Bottineau         12            3.4            1.8            41.7               0.0          

Bowman            13           22.7           22.4            76.9              38.5          

Burke              7            2.3            0.2             0.0               0.0          

Burleigh         422            3.7            3.6            29.1               0.9          

Cass             213            7.6            9.9            62.9               4.7          

Cavalier          24            3.8            2.4            45.8               0.0          

Dickey             5            4.3            2.4            60.0               0.0          

Divide             8            3.8            0.6            25.0               0.0          

Dunn               8            2.1            0.7             0.0               0.0          

Eddy               4            3.0            1.8            50.0               0.0          

Emmons            19            3.6            1.9            31.6               0.0          

Golden Valley      8            1.8            1.9            12.5               0.0          

Grand            139           11.4           11.0            85.6              10.1          
 Forks                                                                                        

Grant              2            9.1            0.8           100.0               0.0          

Griggs            27            3.3            2.0            37.0               0.0          

Hettinger          9            2.5            1.9            22.2               0.0          

Kidder             5            3.0            0.9            20.0               0.0          

Lamoure            9            4.1            3.4            44.4               0.0          

Logan             14            2.6            0.9             7.1               0.0          

McHenry           14            4.9            5.8            35.7               7.1          

McIntosh          20            6.2            2.7            80.0               0.0          

McKenzie          10            2.8            0.7             0.0               0.0          

McLean            24            3.6            3.8            16.7               0.0          

Mercer             8            3.5            1.4            25.0               0.0          

Morton            80            3.7            3.2            28.8               1.3          

Mountrail         24            4.9            5.9            29.2               4.2          

Nelson             1            3.2            0.0             0.0               0.0          

Pembina           16            4.2            4.1            25.0               0.0          

Pierce            10            2.5            2.6            10.0               0.0          

Ramsey             8            3.8            2.2            37.5               0.0          

Ransom            14           11.0            6.4            78.6               7.1          

Renville           9            3.1            1.4            33.3               0.0          

Richland          53            1.8            1.4             9.4               0.0          

Rolette           20            2.4            1.4             5.0               0.0          

Sargent            5            7.5            9.2            40.0              20.0          

Stark             65            3.4            2.6            27.7               0.0          

Steele             3            6.9            3.4           100.0               0.0          

Stutsman         136            4.2            2.5            49.3               0.0          

Towner             3            6.1            1.2           100.0               0.0          

Traill            29            6.5            3.5            51.7               0.0          

Walsh             19           14.7           13.1            68.4              31.6          

Ward              68            3.2            2.9            22.1               0.0          

Wells             14            2.8            1.7            35.7               0.0          

Williams          46            2.4            2.3            13.0               0.0          



TABLE 9

DAY CARE SURVEY STATISTICS BY CITY/COUNTY


                                                                        PERCENT      PERCENT      
                                                                        SAMPLES      SAMPLES      
                              NUMBER                      ARITHMETIC    GREATER      GREATER      
                                OF         ARITHMETIC     STANDARD       THAN         THAN        
COUNTY         CITY           SAMPLES         MEAN        DEVIATION     4 pCi/l      20 pCi/l     

Adams                            6            13.30          7.42         83.3         16.7       

             Hettinger           6            13.30          7.42         83.3         16.7       

Barnes                          33             8.80          7.90        100.0          0.0       

             Litchville          4             6.33          0.65        100.0          0.0       

             Valley City        29             9.14          8.37         72.4         17.2       

Bottineau                       12             3.35          1.81         41.7          0.0       

             Bottineau          12             3.35          1.81         41.7          0.0       

Bowman                          13            22.74         22.37         76.9         38.5       

             Bowman             10            27.15         23.80         70.0         50.0       

             Scranton            3             8.03          0.26        100.0          0.0       

Burke                            7             2.27          0.24          0.0          0.0       

             Bowbells            5             2.28          0.28          0.0          0.0       

             Lignite             2             2.25          0.05          0.0          0.0       

Burleigh                       422             3.72          3.64         29.1          0.9       

             Baldwin             3             2.37          0.19          0.0          0.0       

             Bismarck          385             3.77          3.68         29.9          1.0       

             Lincoln            26             2.13          1.31         11.5          0.0       

             Menoken             3             6.43          0.56        100.0          0.0       

             Bismarck            1             2.70          0.00          0.0          0.0       

             Wing                4             8.40          5.97         50.0          0.0       

Cass                           213             7.58          9.89         62.9          4.7       

             Casselton           5             9.70          3.01        100.0          0.0       

             Fargo             134             7.72          8.65         64.9          5.2       

             Harwood            11             5.78          5.80         63.6          9.1       

             Kindred             5             5.22          0.27        100.0          0.0       

             Mapleton            3             1.53          0.54          0.0          0.0       

             West Fargo         53             8.04         13.84         52.8          3.8       

             Wheatland           2             5.60          1.40        100.0          0.0       

Cavalier                        24            3.80          2.37          45.8         0.0      

             Langdon            24            3.80          2.37          45.8         0.0      

Dickey                           5            4.32          2.37          60.0         0.0      

             Ellendale           5            4.32          2.37          60.0         0.0      

Divide                           8            3.84          0.64          25.0         0.0      

             Crosby              8            3.84          0.64          25.0         0.0      

Dunn                             8            2.13          0.73           0.0         0.0      

             Killdeer            8            2.13          0.73           0.0         0.0      

Eddy                             4            3.03          1.78          50.0         0.0      

             New Rockford        4            3.03          1.78          50.0         0.0      

Emmons                          19            3.55          1.95          31.6         0.0      

             Hazelton            4            1.85          1.48          25.0         0.0      

             Linton             15            4.01          1.80          33.3         0.0      

Golden                           8            1.75          1.89          12.5         0.0      
 Valley                                                                                         

             Beach               8            1.75          1.89          12.5         0.0      

Grand                          139           11.38         10.97          85.6        10.1      
 Forks                                                                                          

             Emerado             3            7.73          6.58          66.7         0.0      

             Grand Forks       132           11.63         11.15          86.4        10.6      

             Larimore            1            0.90          0.00           0.0         0.0      

             Thompson            3            7.43          0.25         100.0         0.0      

Grant                            2            9.05          0.75         100.0         0.0      

             Elgin               2            9.05          0.75         100.0         0.0      

Griggs                          27            3.31          2.02          37.0         0.0      

             Cooperstown        23            2.70          1.38          26.1         0.0      

             Hannaford           4            6.78          1.55         100.0         0.0      

Hettinger                        9            2.54          1.92          22.2         0.0      

             Mott                3            4.83          1.09          66.7         0.0      

             New England         3            1.70          1.24           0.0         0.0      

             Regent              3            1.10          0.57           0.0         0.0      

Kidder                           5            3.02          0.92          20.0         0.0      

             Steele              5            3.02          0.92          20.0         0.0      
 
Lamoure                          9            4.07          3.36          44.4         0.0      

             Edgeley             5            1.08          0.19           0.0         0.0      

             Lamoure             4            7.80          0.47         100.0         0.0      

Logan                           14            2.64          0.93           7.1         0.0      

             Gackle              5            2.52          0.37           0.0         0.0      

             Napoleon            9            2.70          1.12          11.1         0.0      

McHenry                         14            4.94          5.77          35.7         7.1      

             Towner              6            7.83          7.82          50.0        16.7      

             Upham               4            2.50          0.07           0.0         0.0      

             Velva               4            3.03          1.56          50.0         0.0      

McIntosh                        20            6.16          2.72          80.0         0.0      

             Ashley              4            6.80          0.57         100.0         0.0      

             Wishek             16            5.99          3.01          75.0         0.0      

McKenzie                        10            2.79          0.72           0.0         0.0      

             Watford City       10            2.79          0.72           0.0         0.0      

McLean                          24            3.60          3.75          16.7         0.0      

             Garrison            7            1.60          1.06           0.0         0.0      

             Max                 3            0.90          0.00           0.0         0.0      

             Turtle Lake         8            7.15          4.60          50.0         0.0      

             Washburn            6            2.55          0.73           0.0         0.0      

Mercer                           8            3.45          1.38          25.0         0.0      

             Beulah              5            4.26          1.14          40.0         0.0      

             Stanton             3            2.10          0.14           0.0         0.0      

Morton                          80            3.70          3.17          28.8         1.3      

             Hebron              2            4.95          1.05          50.0         0.0      

             Mandan             74            3.67          3.29          29.7         1.4      

             New Salem           4            3.58          0.13           0.0         0.0      

Mountrail                       24            4.90          5.95          29.2         4.2      

             New Town            5            3.44          0.46          20.0         0.0      

             Parshall            4            1.95          1.57          25.0         0.0      

             Plaza               3           19.73          2.95         100.0        33.3      

             Stanley            12            2.79          2.12          16.7         0.0      

Nelson                           1            3.20          0.00           0.0         0.0      

             Lakota              1            3.20          0.00           0.0         0.0      

Pembina                         16            4.23          4.11          25.0         0.0      

             Cavalier           12            4.76          4.63          33.3         0.0      

             St. Thomas          4            2.65          0.32           0.0         0.0      

Pierce                          10            2.45          2.57          10.0         0.0      

             Rugby               7            1.97          0.22           0.0         0.0      

             Wolford             3            3.57          4.48          33.3         0.0      

Ramsey                           8            3.80          2.17          37.5         0.0      

             Devils Lake         5            4.26          2.54          40.0         0.0      

             Starkweather        3            3.03          0.93          33.3         0.0      

Ransom                          14          10.99           6.37          78.6         7.1      

             Enderlin            3            1.80          0.80           0.0         0.0      

             Lisbon             11           13.49          4.71         100.0         9.1      

Renville                         9            3.14          1.41          33.3         0.0      

             Glenburn            9            3.14          1.41          33.3         0.0      

Richland                        53            1.83          1.40           9.4         0.0      

             Barney              1            0.10          0.00           0.0         0.0      

             Colfax              6            0.98          0.38           0.0         0.0      

             Hankinson           4            0.80          0.07           0.0         0.0      

             Wahpeton           38            1.99          1.46          10.5         0.0      

             Wyndmere            4            3.05          0.82          25.0         0.0      

Rolette                         20            2.40          1.44           5.0         0.0      

             Dunseith            5            3.50          1.70          20.0         0.0      

             Rolette             9            2.32          0.53           0.0         0.0      

             Rolla               2            3.80          0.00           0.0         0.0      

             St. John            4            0.50          0.07           0.0         0.0      

Sargent                          5            7.50          9.22          40.0        20.0      

             Forman              1           25.50          0.0          100.0       100.0      

             Milnor              4            3.00          2.23          25.0         0.0      

Stark                           65            3.41          2.61          27.7         0.0      

             Belfield            3            4.17          0.26          66.7         0.0      

             Dickinson          57            3.32          2.65          22.8         0.0      

             South Heart         5            3.98          2.77          60.0         0.0      

Steele                           3            6.87          3.43         100.0         0.0      

             Hope                3            6.87          3.43         100.0         0.0      

Stutsman                       136            4.18          2.48          49.3         0.0      

             Jamestown         129            3.97          2.33          46.5         0.0      

             Montpelier          4            8.43          2.11         100.0         0.0      

             Streeter            3            7.70          0.94         100.0         0.0      

Towner                           3            6.13          1.25         100.0         0.0      

             Cando               3            6.13          1.25         100.0         0.0      

Traill                          29            6.46          3.47          51.7         0.0      

             Buxton              3            2.70          0.22           0.0         0.0      

             Hatton              5            8.58          3.91          80.0         0.0      

             Hillsboro           6            4.02          0.91          16.7         0.0      

             Mayville            6            8.57          3.84          66.7         0.0      

             Portland            9            6.77          2.37          66.7         0.0      

Walsh                           19           14.66         13.15          68.4        31.6      

             Grafton            19           14.66         13.15          68.4        31.6      

Ward                            68            3.24          2.88          22.1         0.0      

             Berthold            1            2.90          0.00           0.0         0.0      

             Minot              67            3.25          2.90          22.4         0.0      

Wells                           14            2.79          1.73          35.7         0.0      

             Harvey             14            2.79          1.73          35.7         0.0      

Williams                        46            2.42          2.32          13.0         0.0      

             Alamo               4            4.23          1.15          50.0         0.0      

             Ray                 5            1.62          1.70          20.0         0.0      

             Wildrose            3            7.67          5.35          66.7         0.0      

             Williston          34            1.86          0.97           2.9         0.0         


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