Date: November 6, 2014

To: Jeff Telander, EPA/OAQPS/SPPD

From: Gabrielle Raymond and Kristin Sroka, RTI International

Subject: Determination of “Non-Detect” Test Data for the BSCP Proposed Rule

I. Introduction

In accordance with section 112 of the Clean Air Act (CAA), the U.S. Environmental 

Protection Agency (EPA) established national emission standards for hazardous air pollutants 

(NESHAP) on May 16, 2003, for the brick and structural clay products (BSCP) manufacturing 

industry. The NESHAP regulated emissions of hydrogen fluoride (HF), hydrogen chloride (HCl), 

and particulate matter (PM)—a surrogate for hazardous air pollutant (HAP) metals—from tunnel 

kilns located at BSCP facilities. On March 13, 2007, the D.C. Circuit Court vacated the emission 

standards for BSCP manufacturing due to issues associated with the methodology used to 

determine the minimum regulatory “floors” for new and existing units.1 Therefore, the EPA is 

proposing new standards for BSCP manufacturing, including standards for HF, HCl, chlorine 

(Cl2), mercury (Hg), and non-Hg HAP metals (or PM surrogate). The objective of this 

memorandum is to describe the determination of “non-detect” EPA Method 29 (multi-metals) 

and EPA Method 23 (dioxin/furan) test data for evaluation in the setting of numeric MACT floor

standards versus establishing work practice standards for the BSCP proposed rule.

II. Sources and Pollutants Evaluated

For BSCP tunnel kilns, the run flags for each HAP metal, including Hg, and each 

dioxin/furan toxic equivalent (TEQ)2 test run were evaluated to determine the “non-detect” status 

of the run. In addition, for BSCP dryers, each dioxin/furan run flag was evaluated to determine 

the “non-detect” status of the run. The guidelines from EPA’s memorandum Determination of 

“non-detect” from EPA Method 29 (multi-metals) and EPA Method 23 (dioxin/furan) test data 

when evaluating the setting of MACT floors versus establishing work practice standards

(Johnson, 2014) were followed for each evaluation.

 1 Sierra Club v. EPA, 479 F.3d 875 (D.C. Cir. 2007). 2 For these runs, dioxin/furan emissions are expressed in terms of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic 

equivalents (TEQ).
2

III. Definitions from Guidance Memorandum (Johnson, 2014)

The following definitions appear in the Johnson guidance memorandum (2014) and also 

apply to this memorandum:

ADL (Above Detection Limit): Results from the lab show measured values above the 

MDL. (Be sure to distinguish reported values as being above the MDL versus above the RL or 

other lab ‘confidence’ level).

BDL (Below Detection Limit): A laboratory result where detectable amounts of an 

individual pollutant or congener are not found. Again, evaluate the data to ensure BDL means 

“below MDL” and not “below RL” or some other ‘confidence’ level.

DLL (Detection Limit Limited): A test result where some fractions of the analysis 

return detectable amounts of a pollutant or congener (above MDL), while other fractions are 

BDL.

EDL (Estimated Detection Limit): For Dioxin/Furan tests, a commonly reported 

estimate of the concentration where a given analyte would have to be present to produce a signal 

with a peak height of at least 2.5x the background noise signal level. The EDL determination is 

done for each sample set at the time of analysis. This is specific to the analytical technique and is 

affected by factors such as sample size, dilution, etc., commonly reported for non-detected 

analytes instead of other values such as PQL, RL, QL, etc. It is important to note that EDL and 

MDL are not the same, but EDL is a standard benchmark for determining detection from an 

isotope dilution analysis, common to dioxin/furan emission testing.

MDL (Method Detection Limit): Synonymous with the term LOD (Level of Detection) 

the MDL is defined as the lowest quantity of a substance that can be distinguished from the 

absence of that substance (i.e. a blank value) with a stated level of confidence. For the purposes 

of this document, the process of identifying the MDL of a given substance is defined in EPA 

Method 301, Section 15.

RDL (Representative Detection Limit): Sometimes referred to as the Representative 

Method Detection Limit (RMDL) this is the mean MDL value of a specific analyte determined 

by an MTG review of l lab analyses represented by labs who provided data for best performing 

sources, thereby creating a representative value by which to assess detection such that the best 

performing lab handing any particular analytical sample does not drive all detection limit 

discussion and decision making. By establishing this value as the mean of several labs we allow 

for the selection of local and cost effective analysis of environmental samples while maintaining 

a balance of quality analyses. The Westlin/Merrill memorandum defines RDL for dioxin/furans 

as EDL x 2 (Westlin and Merrill, 2011).

IV. Run Flags

Run flags are determined by the facility/analytical laboratory for each run. They compare 

each analytical fraction mass to the MDL or other detection limit values (e.g., Reporting Limit) 

as available. Mercury runs have five analytical fractions and the other HAP metals have two 

analytical fractions. The run flag is BDL if all of the fraction masses are below the MDL, DLL if 
3

one or more of fraction masses are below the MDL, and ADL if all of the fraction masses are 

above the MDL. Similarly, for dioxin/furan testing, there are multiple congeners for each TEQ 

run. The run flag is BDL if all of the congener masses are below the MDL; DLL if one or more 

congeners are below the MDL; and ADL if all the congeners are above the MDL. For each 

fraction/congener mass that is below the MDL, the MDL mass is used for the fraction/congener 

mass and subsequent emissions calculations.

V. Mercury

For each tunnel kiln with Hg test data, each run flag was evaluated to determine the “nondetect” status of the run, according to Johnson (2014). If the run flag was ADL or DLL, the run 

was considered ADL. If the run flag was BDL, the run mass (sum of five fraction masses, as 

available) was evaluated and compared to the RDL value provided in the guidance document

Data and procedure for handling below detection level data in analyzing various pollutant 

emissions databases for MACT and RTR emissions limits (Westlin and Merrill, 2011) for Hg 

analyzed by Cold Vapor AA, 0.56 μg. If the run mass was less than the RDL, the run was 

considered BDL. If the run mass was greater than the RDL and was based on MDL values, the 

run was considered BDL. If the run mass was greater than the RDL and was based on other 

detection limit values (e.g., Reporting Limit), the data was set aside and not used for the analysis. 

(Note that data set aside for this analysis were not set aside for actual MACT floor rankings and 

floor calculations.) The following figure displays the steps in determining the “non-detect” 

status of a run for this analysis based on the guidance provided by Johnson (2014).
4

Figure 1. Steps in determining the “non-detect” status of test run data for setting MACT 

floors.

Table 1 displays the percentage of ADL and BDL runs for Hg from BSCP tunnel kilns.

The run-by-run data used to calculate the percent ADL and BDL for Hg from BSCP tunnel kilns 

can be found in Appendix A.

Table 1. Percent ADL and BDL for Hg from BSCP Tunnel Kilns

Hg

Total Runs 55

No. Set Aside 6

No. Used 49

No. BDL 0

No. ADL 49

% BDL 0

% ADL 100
5

The percent BDL for BSCP tunnel kilns was 0 percent; as such, the EPA is proposing a 

MACT floor standard for Hg for BSCP tunnel kilns.

VI. Non-Hg HAP Metals

For each tunnel kiln with non-Hg HAP metals test data, each run flag was evaluated to 

determine the “non-detect” status of the run, according to Johnson (2014). If the run flag was

ADL or DLL, the run was considered ADL. If the run flag was BDL, the run mass (sum of each 

fraction mass) was evaluated and compared to the RDL value provided in the guidance document 

(Westlin and Merrill, 2011) for each individual non-Hg HAP metal analyzed by either 

Inductively Coupled Plasma/Mass Spectrometry or Graphite Furnace Atomic Absorption 

Analysis [ICP/MS or GFAAA] or Inductively Coupled Atomic Emission Spectroscopy or 

Atomic Absorption Analysis [ICP/AES or AA]. Table 2 presents the RDL values for each nonHg HAP metal for each analytical method.

Table 2. RDL values for each Non-Hg HAP Metal per Analytical Method (Westlin and 

Merrill, 2011)

Method 29 Non-Hg 

HAP Metals

ICP/AES or AA

RDL (μg)

ICP/MS or GFAA

RDL (μg)

Antimony 1.2E+01 1.1E+00

Arsenic 1.9E+01 4.0E-01

Beryllium 1.1E-01 8.0E-02

Cadmium 1.5E+00 3.0E-02

Chromium 2.5E+00 3.0E-01

Cobalt 2.5E+00 3.0E-01

Lead 1.5E+01 3.0E-01

Manganese 7.0E-01 3.0E-01

Nickel 5.4E+00 5.4E+00

Selenium 2.7E+01 8.0E-01

If the run mass was less than the RDL, the run was considered BDL. If the run mass was 

greater than the RDL and was based on MDL values, the run was considered BDL. If the run 

mass was greater than the RDL and was based on other detection limit values (e.g., Reporting 

Limit), the data was set aside and not used for the analysis. (Note that data set aside for this 

analysis were not set aside for actual MACT floor rankings and floor calculations.) Table 3

displays the percentage of ADL and BDL runs for each non-Hg HAP metal from BSCP tunnel 

kilns. The run-by-run data used to calculate the percent ADL and BDL for each non-Hg HAP

metal from BSCP tunnel kilns can be found in Appendix B.
6

Table 3. Percent ADL and BDL for Each Non-Hg HAP Metal from BSCP Tunnel Kilnsa

Sb As Be Cd Cr Co Pb Mn Ni Se

Total 

Non-Hg 

HAP 

Metals

Total Runs 52 52 52 52 52 52 52 41 52 52 509

No. Set Aside 24 24 36 18 0 19 6 0 1 14 139

No. Used 28 28 16 34 52 33 46 41 51 38 370

No. BDL 12 6 16 1 0 11 11 0 0 0 60

No. ADL 16 22 0 33 52 22 35 41 51 38 310

% BDL 43 21 100 3 0 33 24 0 0 0 16

% ADL 57 79 0 97 100 67 76 100 100 100 84

a Sb = antimony; As = arsenic; Be = beryllium; Cd = cadmium; Cr = chromium; Co = cobalt; Pb = lead; Mn = 

manganese; Ni = nickel; Se = selenium.

The majority of the individual non-Hg HAP metals had a high percentage of runs above 

detection level, thus not meeting the criteria for a work practice standard. As a result, the EPA is 

proposing MACT floor standards for PM as a surrogate for non-Hg HAP metals for BSCP tunnel 

kilns.

VII. Dioxin/Furan (TEQ)

Seventeen specific dioxin/furan congeners are considered in the calculation of TEQ 

values. For the 17 specific dioxin/furan congeners, the mass reported in the laboratory analysis 

of the test report was multiplied by the 2005 World Health Organization (WHO) toxic equivalent 

factors (TEF) to calculate the TEQ value for each run. If the mass for the congener was flagged 

as BDL, then a value of zero was used as the mass. The mass of each of the 17 calculated TEQ 

values were summed together to get a total TEQ mass for each run.

The total TEQ mass for each run was compared to the Utilities TEQ EDL, 0.018 ng

(Westlin and Merrill, 2011). If the total TEQ mass was greater than the EDL, the run was 

considered ADL. If the total TEQ mass was less than the EDL, the run was considered BDL.

Table 4 summarizes the overall percentage of ADL and BDL runs for BSCP tunnel kilns 

and dryers. The run-by-run data used to calculate the overall percent ADL and BDL for TEQ 

from BSCP tunnel kilns and dryers can be found in Appendix C.

Table 4. Percent ADL and BDL for TEQ from BSCP Tunnel Kilns and Dryers

Source No. Runs % ADL % BDL

Overall for BSCP Tunnel Kilns 18 17 83

Overall for BSCP Dryers 12 0 100
7

The percent BDL for kilns was 83 percent; thus, the EPA is proposing a work practice 

standards for dioxins/furans (TEQ) for BSCP tunnel kilns.

The percent BDL for dryers was 100 percent; thus, the EPA is proposing no limit for 

dioxins/furans (TEQ) for BSCP dryers.

VIII. References

Johnson, S. 2014. Determination of “non-detect” from EPA Method 29 (multi-metals) and EPA 

Method 23 (dioxin/furan) test data when evaluating the setting of MACT floors versus 

establishing work practice standards. Memorandum from Steffan Johnson, SPPD, MPG, to 

SPPD management and MACT rule writers. June 5, 2014.

Westlin, P., and R. Merrill. 2011. Data and procedure for handling below detection level data 

in analyzing various pollutant emissions databases for MACT and RTR emissions limits. 

Memorandum from Peter Westlin, SPPD, MPG and Raymond Merrill, AQAD, MTG, to 

SPPD management and MACT rule writers. December 13, 2011.
Appendix A

BSCP Tunnel Kiln Hg Data
A-1

The run-by-run data used to calculate the percent ADL and BDL for Hg from BSCP tunnel kilns 

are provided in the corresponding Appendix A Microsoft Excel® file

 
Appendix B

BSCP Tunnel Kiln Non-Hg HAP Metal Data
B-1

The run-by-run data used to calculate the percent ADL and BDL for non-Hg HAP metals from 

BSCP tunnel kilns are provided in the corresponding Appendix B Microsoft Excel® file.
Appendix C

BSCP Tunnel Kiln and Dryer TEQ Data
C-1

The run-by-run data used to calculate the percent ADL and BDL for TEQ from BSCP tunnel 

kilns and dryers are provided in the corresponding Appendix C Microsoft Excel® file.