Identifying an Analytical Method for 1,4-Dioxane in Drinking Water
Summary of Issue:
In conjunction with its update of the toxicological basis of its drinking water guidance value for
1,4-dioxane, the MassDEP Office of Research and Standards (ORS) sought input from the analytical
community on the feasibility of detecting 1,4-dioxane at a concentration ten-fold lower than its existing
guidance value. Based on information indicating that the analytical capability exists to detect 1,4dioxane at this lower concentration, ORS plans to set the new guideline at its health-based level. This is
an Office of Research and Standards Guideline (ORSG) which is presented for the convenience of those
who have to interpret data on 1,4-dioxane in drinking water or other water resources. As such there is
no Massachusetts mandated requirement for routine monitoring of this chemical.
Health Basis:
ORS periodically updates its drinking water guidance to reflect new toxicity information issued
by the US Environmental Protection Agency (US EPA). ORS evaluates both the non-cancer and cancer
information and sets a health-based guidance value that is protective for both non-cancer and cancer
health endpoints. The cancer-based toxicity value is set at a concentration corresponding to an Excess
Lifetime Cancer Risk of one in one million, or a one-in-a-million chance of getting cancer above
background cancer incidence upon daily exposure to that concentration for a lifetime. In the last year,
the US EPA revised its cancer potency estimate for 1,4-dioxane by about ten-fold, resulting in a ten-fold
decrease in the toxicological basis of the drinking water guidance value for 1,4-dioxane. The current
ORSG for 1,4-dioxane, last updated in 2004, is 3.0 ppb. The toxicologically-based value determined in
this 2011 most recent update is 0.3 ppb.
Analytical Capabilities:
One of the considerations in setting drinking water criteria for chemicals is the capability for
quantitating the chemical analytically at concentrations as least as low as the criterion level. This level is
designated as the analytical Practical Quantitation Limit (PQL) or Reporting Limit (RL). A drinking water
guidance value cannot be set at a concentration below the concentration at which it can be quantified.
If a health-based guidance value for a chemical is below the analytical detection limit for that chemical,
the guidance value is set at that detection limit. It is therefore important that the detection limit
identified balances the need to detect concentrations of potential toxicological concern with the need to
select a detection limit that can be routinely and reliably achieved by the laboratory community.
In order to determine the existing capabilities for detecting such a low concentration of this
chemical, ORS contacted Ann Marie Allen from the MassDEP Wall Experiment Station (WES) to discuss
what an achievable and reasonable PQL for 1,4-dioxane might be. While WES does not typically analyze
for this contaminant, she indicated that a variety of modified methods and protocols were currently
being used spanning a range of detection limits.
EPA Region 1 had a 2003 Standard Operating Procedure (SOP) for 1,4-dioxane with a noted PQL
of 1.0 ppb, which was referenced in ORS’ documentation for its 2004 1,4-dioxane guideline. The Region
1 SOP has been updated with a new PQL of 2.0 ppb (US EPA/Reg1, 2004). The reason for this update
was not clear and ORS was unsuccessful in finding a person with whom to discuss this from the Region 1
office.
MassDEP Office of Research and Standards
1
May 2011
The state’s Laboratory Advisory Committee was polled in an attempt to assess current
laboratory capabilities for quantitating 1,4-dioxane in drinking water. The responses to the query
received are tabulated in Table 1 and indicate that a range of methods with varying quantitation
capabilities are in use.
One of the methodologies identified during this poll was EPA Method 522 entitled
“Determination of 1,4-Dioxane in Drinking Water by Solid Phase Extraction (SPE) and Gas
Chromatography/Mass Spectrometry (GC/MS) with Selected Ion Monitoring (SIM)”
(http://www.epa.gov/microbes/ordmeth.htm). This method was recently developed in conjunction
with the EPA Unregulated Contaminant Monitoring Rule (UCMR) with the capacity to detect extremely
low levels of this compound. ORS contacted Paul Grimmett of EPA, one of the authors of this method,
to discuss whether this method could routinely detect 1,4-dioxane in drinking water at concentrations at
or around the proposed 0.3 ppb revised toxicologically-based guidance level.
EPA Method 522 has been approved for over a year. The method was developed for the EPA
UCMR in order to provide a standard method to be used during nationwide testing for 1,4-dioxane
under UCMR3 and in anticipation of EPA possibly developing a guidance value for 1,4-dioxane. This
method meets US EPA’s criteria for a standardized method for a nationwide study (personal
communication, P. Grimmett): utilizes instrumentation typically found in analytical laboratories and
uses materials commercially available from multiple vendors easily accessible in the U.S. The method
uses solid-phase microextraction (SPME) coupled with GC-MS. The MDL for this method is in the range
of about 0.02 ppb. In place of the PQL, EPA now uses a parameter called the single laboratory lowest
concentration minimum reporting level (LCMRL). The LCMRL is defined as the lowest true concentration
for which the future recovery is predicted to fall, with high confidence (99%), between 50% and 150%
recovery (EPA’s performance criteria). The LCMRL determined in the method is in the range of about
0.04 ppb. This is the same method used by the state of Florida, for which the Florida lab reports an RL of
about 0.4 ppb. Additional documentation and information for Method 522 can be found in Grimmett
and Munch (2009) and additional technical information on the LCMRL can be found in US EPA (2010).
Method 522 will be cited as an available analytical method in ORS’ documentation for the
revised 1,4-dioxane guideline. ORS is not mandating that this method be used as there are other
modified methods that laboratories are presently using or could use to achieve the same level of
sensitivity. ORS is using the capability of this method to detect concentrations well below the updated
ORSG as appropriate justification to set the revised guideline for 1,4-dioxane at the toxicity-based
concentration of 0.3 ppb.
References:
Grimmett, Paul E. and Jean W. Munch. 2009. Method Development for the Analysis of 1,4-Dioxane in Drinking Water Using
Solid-Phase Extraction and Gas Chromatography-Mass Spectrometry. Journal of Chromatographic Science. 47:31-39.
US EPA (US Environmental Protection Agency). 2008. Determination of 1,4-Dioxane in Drinking Water By Solid Phase
Extraction (SPE) and Gas Chromatography/Mass Spectrometry (GC/MS) with Selected Ion Monitoring (SIM) (version 1).
EPA/600/R-08/101. National Exposure Research Laboratory. Office of Research and Development.
http://www.epa.gov/microbes/ordmeth.htm
US EPA (US Environmental Protection Agency). 2010. Technical Basis for Lowest Concentration Minimum Reporting Level
(LCMRL) Calculator. (EPA 815-R-11-001). Office of Water (MLK 140).
http://water.epa.gov/scitech/drinkingwater/labcert/upload/LCMRLTechRpt.pdf.
MassDEP Office of Research and Standards
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May 2011
US EPA/Reg1 (US Environmental Protection Agency Region 1 New England). 2004. Standard Operating Procedure for
Measurement of Purgeable 1,4-Dioxane in Water by GC/MS - Revision 3. (EIASOP-VOADIOX3). The Office of Environmental
Measurement and Evaluation. EPA Region 1 New England. North Chelmsford, Massachusetts. pp. 1-124. http://www.cluin.org/download/contaminantfocus/dioxane/EIASOP-VOADIOX3.pdf.
MassDEP Office of Research and Standards
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May 2011
Table 1. Summary of 1,4-Dioxane Detection
Limits in Drinking Water from Informal Survey
of Massachusetts Laboratories
Laboratory
METHOD
#
MDL
RL/PQL
(g/L)
(g/L)
1a
8260 SIM
1.4
1b
8270 SIM
0.07
2
modified 8260b SIM
0.2
3
modified 524.2 SIM
0.3-1.0
4a
8260 SIM
3.0
4a
8260 full scan
200.0
4b
8270 SIM
0.5
5
EPA 522
0.10
0.4
6
Modified 8270
0.23
0.5
7
EPA 8260B
100.0
7
8270C SIM LVI isotope dil
< 1.0
8
modified 8270
0.2
1.0
9
8260 SIM
0.5
2.0
9
8270
1.0
5.0
9
8270 SIM
0.05
0.1
10
GC/MS full scan
MassDEP Office of Research and Standards
2.0
4