TL: LIMITATIONS OF HISTORIC AND CURRENT METHODS FOR MEASURING
POLYCHLORINATED DIOXINS AND FURANS IN INCINERATOR EMISSIONS
SO: Pat Costner, GREENPEACE INTERNATIONAL, (GP)
DT: 11 MAY 1993D

Methods currently used for measuring the concentrations of
polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDFs)
in stack gases of incinerators and other combustion devices may
reflect no more than 21-26 percent of the PCDD/PCDFs actually
present in such stack emissions. I.e., actual emissions of
PCDD/PCDFs may be 4-5 times higher than those measured by
USEPA's MM5 and M23 procedures.

U.S. EPA Modified Method 5 - MM5 (Coates, 1990)

In their 1990 report, "Validation of Emission Test Method for
PCDDs and PCDFs," USEPA examined the precision and accuracy of
the Modified Method Five (MM5) sampling and analysis scheme for
polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/
PCDFs) in municipal waste combustor stack gas. The MM5 is also
the designated method for assessing the PCDD/PCDF concentrations
in the emissions of other point-sources, including hazardous
waste incinerators, cement kilns, and medical waste
incinerators. 

In their assessment of MM5, USEPA scientists measured the
recovery of statically and dynamically spiked PCDD/PCDF
congeners. For dynamic spiking, a system was designed that
continuously delivers isotopic PCDD/PCDF congeners into the
sampling train during sampling of actual incinerator stack gas.

In the laboratory, recoveries of dynamically spiked PCDD/PCDFs
ranged from 50% to 99% for the low spike (5 nanograms) and from
69% to 97% for the high spike (500 nanograms). However, at the
full-scale incinerator, "recovery of the dynamic spikes had an
overall average of 21% and were moderately variable."

In this study, USEPA also investigated methods for improving
spike recoveries and, hence, the overall accuracy and precision
of MM5. For example, by extracting sample filters with benzene
rather than dichloromethane, which is specified in the method,
the overall recovery of dynamically spiked isotopic PCDD/PCDFs
was increased to 26%. 

Considerably greater improvements were noted when the back-half
glassware of the MM5 sampling train was coated with a thin layer
of Apiezon-L grease. At the full-scale incinerator, rinsing the
Apiezon-L coated back-half glassware with toluene resulted in
recoveries ranging from 62.9% to 107%, although precision was
relatively poor.

U.S. EPA Method 23 -- M23 (USEPA, 1991)

On February 13, 1991, USEPA promulgated the final rule for the
testing procedure for PCDD/PCDFs from stationary point-sources.
According to the Agency, this procedure, Method 23 or simply
"M23", is derived from MM5, with some changes in the quality
assurance requirements and the solvents used to recover the
sample. For example, the filter and solid adsorbent are
extracted in the laboratory with toluene. 

USEPA did not incorporate into M23 those previously described
changes which led to markedly higher recoveries during dynamic
spiking. In other words, since the only substantive difference
between MM5 and M23 is the substitution of toluene for
dichloromethane, overall recovery of M23 can be expected to be
at or near the 26% achieved with benzene, as discussed above. 

References

(Coates, 1990) Coates, J.T., "Validation of Emission Test Method
for PCDDs and PCDFs," EPA/600/3-90/007, U.S. Environmental
Protection Agency, Research Triangle Park, NC, March 1990

(USEPA, 1991) United States Environmental Protection Agency,
"Standards of Performance for New Stationary Sources; Addition
of Methods for Measurement of Polychlorinated Dibenzo-p-Dioxins,
Polychlorinated Dibenzofurans, and Hydrogen Chloride Emissions
From Stationary Sources," Federal Register, Vol. 56, No. 30,
Wednesday, February 13, 1991, pp. 5758-5775