Status of Ambient Measurement Methods for Hazardous Air Pollutants An EPA-sponsored survey points out the need for continued methods development for the Clean Air Act R. M U K U N D , T H O M A S J. KELLY, S Y D N E Y M . M E L I N D A J. H A Y S , W I L L I A M A.
T
he 1990 Clean Air Act Amendments (CAAA) have refocused attention on ambient air toxics. Title III of the CAAA seeks to reduce the public health risks from 189 hazardous air pollutants (HAPs) in ambient air through congressionally mandated riskreduction timetables and goals for HAP emission controls and other requirements (i). Health risk determination and the quantification of reductions in health risks requires knowledge of ambient HAP concentrations and, by extension, the availability of adequate ambient HAP measurement methods. However, a s s e s s m e n t s of the c u r r e n t d a t a b a s e of information available on ambient concentrations and transformation products, recently reported in ES&T (2), found a paucity of data needed to conduct adequate health risk assessments for many HAPs (3, 4). For example, the survey showed no ambient data for 74 of the 189 HAPs. The principal reason for the absence of ambient data for many HAPs has been suggested as a lack of suitable ambient air sampling and analysis methods. Here we discuss an EPA-sponsored survey (5) of the current status of ambient measurement methods for the 189 HAPs that found 180 different candidate methods that are currently in various stages of development. This survey found that only 126 of the 189 HAPs have methods that are reasonably established for ambient air measurements, although all of these methods are EPA-approved or well demonstrated for ambient monitoring. Of the remainder, 53 HAPs have methods that are reasonably established for nonambient air, such as for workplace or stack emissions measurements, and which could likely be developed for ambient air applications. Of the 10 remaining HAPs, six have methods that are potentially applicable to ambient air measurements following extensive further development, and four others have no methods currently in any stage of development.
0013-936X/95/0929-183AS09.00/0 © 1995 American Chemical Society
GORDON
McCLENNY
Ambient methods development research has resulted in a variety of measurement methods, particularly for volatile organics, semivolatile organics, and particulate-phase inorganics. Many of these methods, such as those in the Intersociety Committee (ISC) methods compilation (6) and the EPA's Toxic Organics (TO) compendium (7), target individual chemicals on the 189 HAPs list. However, the 189 HAPs are a varied collection of individual chemicals and generic compound groups, and include industrial chemicals, pesticides, solvents, metals, and combustion byproducts. Although some of the HAPs have long been measured in ambient air, many others— assigned to the list based on their toxicity in workplace environments—are not typically measured or even considered in ambient air. The diversity of the HAPs is a principal factor in this survey's recommendation for continued ambient measurements methods development.
Survey approach This survey differed substantially from previous reviews (8,9) of possible measurement methods for the 189 HAPs in both approach and scope. The survey initially compiled key physical and chemical properties of the HAPs. These properties were used to group the HAPs into classes of compounds and, subsequently, to conduct evaluations of the applicability of individual measurement methods. Following the division of the 189 HAPs into organic and inorganic compounds, vapor pressure (VP, mmHg at 25 ° C and boiling point (and/or melting point) data were compiled for all HAPs. VP data were used to categorize and rank die 189 HAPs, using quantitative (but subjective) VP criteria to define very volatile (VP > 380 mmHg) organic compounds (WOC: 15 HAPs) and very volatile inorganic compounds (WINC: 6 HAPs); volatile (VP = 0.1-380 mmHg) organic compounds (VOC: 82 HAPs) and volatile inorganic compounds (VINC: 3 HAPs); VOL. 29, NO. 4, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY • 1 8 3 A
Format used in the HAPs methods survey report9
Compound
CAS no.
Compound class
Acetaldehyde
75-07-0
WOC
Acetamide
60-35-5
SVOC
Acetonitrile
75-05-8
VOC
3
Ambient measurement method "Applicable"'
"Likely"
TO-5 TO-11
R-4[14]
"Potential"
Limit of detection TO-5:1 ppbv; TO-11:1 ppbv; [14]: 30 ppmv
OSHACIM [A625]; R-37; R-47
R-1, CLP-1A, R-3
Comment
[A625]; not a validated method; R-47: method developed for analysis of water R-1:1 ppbv
Reference 3. " Designation as an "applicable" method for a specific HAP does not necessarily imply certification or approval of the method by EPA for ambient air measurements of that HAP.
semivolatile (VP = 10~7-0.1 mmHg) organic compounds (SVOC: 64 HAPs) and semivolatile inorganic compounds (SVINC: 2 HAPs); and nonvolatile (VP
