14 Application of the Preliminary Pollutant Limit Value (PPLV) Environmental Risk Assessment Approach to Selected Land Uses DAVID H. ROSENBLATT, MITCHELL J. SMALL, and ROBERT J. KAINZ U.S. Army Medical Bioengineering Research & Development Laboratory, Fort Derrick, Frederick, MD 21701
The s i t e - s p e c i f i c P r e l i m i n a r y P o l l u t a n t L i m i t Value (PPLV) process f o r environmental r i s k assessment has been a p p l i e d to contaminated land areas i n order to determine what use might be made of them at v a r i o u s l e v e l s of contamination. The process i n v o l v e s examin a t i o n of the p o t e n t i a l f o r each chemical of concern to proceed from the soil or water, through defined pathways, to man or other target organisms. Each pathway i s treated as if it c o n s i s t e d of a s e r i e s of compartments at e q u i l i b r i u m , except that the exposure of man to the l a s t of these compartments i s handled as a consumption r a t e process. The best a v a i l a b l e t o x i c o l o g i c a l information i s used to estimate an acceptable d a i l y dose, ( D ) , f o r human (or other organism) exposure to each compound. This value i s used to c a l c u l a t e l e v e l s of the compound i n the soil or water such that D i s not likely to be exceeded during the course of s p e c i f i e d c a t e g o r i e s of human activity. A PPLV i s derived from c o n s i d e r a t i o n of the DT along with the probable exposure level. Four s p e c i f i c examples of the use of the PPLV concept are described to illustrate how the concept i s a p p l i e d i n r e a l world s i t u a t i o n s . S o i l and water PPLVs are developed f o r s e v e r a l compounds. These PPLVs vary according to envisioned s c e n a r i o ; f o r example, subsistence farming, r e s i d e n t i a l housing, hunting, f i s h i n g , and i n d u s t r i a l or timbering o p e r a t i o n s . Each scenario e n t a i l s one or more exposure pathways. The PPLVs so derived allow f o r various options f o r cleanup or r e s t r i c t i o n of land use, such that p u b l i c h e a l t h will not be jeopardized by r e s i d u a l contamination. Each p o t e n t i a l cleanup e f f o r t represents a d i f f e r e n t l e v e l of hazard r e d u c t i o n . The PPLV concept facilitates d e c i s i o n s as to the e f f e c t i v e use of l i m i t e d d o l l a r s to clean a s i t e to a l e v e l of intended use. T
T
This chapter not subject to U.S. copyright. Published 1983, American Chemical Society
264
FATE OF CHEMICALS IN THE ENVIRONMENT
The US Army, which f o r s e v e r a l years has had r e s p o n s i b i l i t i e s f o r renovating contaminated t r a c t s of land, has developed a conceptual framework that can accommodate a v a r i e t y of d e c i s i o n making processes and models to respond to the question, "How c l e a n i s clean?" This approach focuses on determining acceptable p o l l u t a n t residue l e v e l s as goals f o r remedial a c t i o n . I t recognizes that p o t e n t i a l land use, courses of remedial a c t i o n , the nature and extent of contamination, and the population at r i s k are a l l c o n s i d e r a t i o n s that may a f f e c t those g o a l s . Despite i t s f l e x i b i l i t y , the Army methodology can be described w e l l i n terms of referenced s c i e n t i f i c estimation methods or c o r r e l a t i o n s and i n terms of r e c e n t l y developed paradigms. The Army's P r e l i m i n a r y P o l l u t a n t L i m i t Value (PPLV) concept (1,2,3), a d e c i s i o n t o o l , i s being used and c o n t i n u a l l y improved. The s i t e - s p e c i f i c PPLV process involves examination of the p o t e n t i a l f o r each chemical of concern to proceed from i t s p o i n t ( s ) of o r i g i n i n the s o i l or water, through defined pathways, to the target organism, t y p i c a l l y man ( F i g u r e 1). For human t a r g e t s , the compartments along the pathway are assumed to be at e q u i l i b r i u m , except that human exposure i s handled as a rate process ( F i g u r e 2 ) . I t must be assumed that the compound of i n t e r e s t does not decompose and that i f decomposition does occur, the hazard i s reduced rather than i n c r e a s e d . In cases where t h i s does not hold true and where products pose s e r i o u s problems, i n d i v i d u a l d e t e c t i o n , i d e n t i f i c a t i o n , and e v a l u a t i o n should be undertaken to address the decomposition products, t r e a t i n g them as new compounds. The best a v a i l a b l e t o x i c o l o g i c a l information i s used to estimate an acceptable d a i l y dose, D , f o r human exposure to each compound. T h i s i s then used to c a l c u l a t e l e v e l s of the compound i n the s o i l or water such that D^ i s not l i k e l y to be exceeded during the course of s p e c i f i e d c a t e g o r i e s of human a c t i v i t y . A PPLV i s derived from c o n s i d e r a t i o n of the D along with the probable exposure l e v e l . PPLVs vary according to envisioned s c e n a r i o , e.g., subsistence farming, r e s i d e n t i a l housing, hunting, f i s h i n g , and i n d u s t r i a l or timbering operat i o n s . Each scenario e n t a i l s one or more exposure pathways. PPLVs permit assessment of the various options f o r cleanup or r e s t r i c t i o n of land use, such that p u b l i c h e a l t h w i l l not be jeopardized by r e s i d u a l contamination. Each p o t e n t i a l remedial a c t i o n represents a d i f f e r e n t l e v e l of hazard r e d u c t i o n . The PPLV concept c o n t r i b u t e s to c o s t - e f f e c t i v e d e c i s i o n s on the use of funds f o r such remedial a c t i o n s , i n accordance with intended l e v e l s of use. The PPLV process has been a p p l i e d i n s e v e r a l c o n t e x t s . Each a p p l i c a t i o n has revealed new aspects that had not been considered p r e v i o u s l y (Table I ) . Nevertheless, the examples share one c h a r a c t e r i s t i c common to t o x i c chemical r i s k a n a l y s i s ; an acceptable exposure l e v e l must be combined with a r e l a t i o n ship between source c o n c e n t r a t i o n and estimated degree of exposure• T h i s concept has been published p r e v i o u s l y ( 1 , 2 , 3 ) ; T
T
14.
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Preliminary Pollutant Limit Value Process
Figure 1. Pathways from s o i l v i a water, p l a n t , and animal compartments to man.
265
266
FATE OF CHEMICALS IN THE
ENVIRONMENT
F i g u r e 2. The pathway f r o m s o i l v i a w a t e r , p l a n t s , and a n i m a l s t o man. I n t h i s f a t e m o d e l , t h e a c c e p t a b l e d a i l y dose o f t o x i c a n t , D^, c a n be o b t a i n e d from s e v e n s o u r c e s o f l i t e r a t u r e information. The e q u a t i o n f o r a c c e p t a b l e d a i l y dose i s : D
T
=
=
K
BW
Table I .
PPLV Studies Related to Selected Land Uses
Site (Ref)
Scenarios and Associated Pathways Scenarios Pathways
Alabama AAP (4)
Subsistence agriculture
Vegetable consumption Livestock consumption Dairy consumption Soil ingestion
Residential housing
Vegetable consumption Soil ingestion
Apartment housing
Soil ingestion
Compounds of P o t e n t i a l Concern at S i t e
2,4,6-Trinitrotoluene (TNT) 2,4-Dinitrotoluene (DNT N-Methyl-N,2,4,6-tetranitroaniline (Tetryl) 1,3,5-Trinitrobenzene (TNB) 1,3-Dinitrobenzene (DNB) Diphenylamine Aniline N,N-Dimethylaniline Nitrobenzene Nitrocellulose Lead 3
14.
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267
Table I — c o n t i n u e d
Savanna ADA C5)
Gratiot County Landfill (6)
Bangor Naval Submarine Base
a. b. c.
Industrial
Dust inhalation
Hunting
Meat consumption
Timber harvesting
Dust inhalation
Recreational fishing
Sediment to bottom feeders
TNT DNT TNB
Downriver drinking water supply
Dry lagoons leaching to river
Hexahydro1,3,5-trinitro1,3,5-triazine (RDX)
Subsistence agriculture
Livestock (soil)
Polybromobiphenyls (PBBs)
Residential housing
Water ingestion
Industrial
Dust i n h a l a t i o n or water ingestion
Recreational fishing
F i s h and shellfish consumption
TNT RDX Picric acid Picramic a c i d Propylene g l y c o l d i n i t r a t e (PGDN) c
c
Not a t o x i c hazard. Lead presents some complex problems. These were discussed at length by two of the present authors (Ref. _4). P i c r i c and picramic acids are s t r o n g l y i o n i z e d . Not enough i s known of t h e i r b i o c o n c e n t r a t i o n behavior to permit c a l c u l a t i o n of a b i o c o n c e n t r a t i o n f a c t o r ; hence, they w i l l not be discussed f u r t h e r i n the present r e p o r t .
FATE OF CHEMICALS IN THE ENVIRONMENT
268
the present report concentrates on i t s use i n d e r i v i n g values a s s o c i a t e d with s e l e c t e d land uses. Acceptable D a i l y Doses
limit
(Dj)
The acceptable d a i l y dose of a t o x i c a n t ( i n mg/(kg x d a y ) ) , Drp, r e l a t i v e to chronic human h e a l t h e f f e c t s , i s c e n t r a l to PPLV c a l c u l a t i o n s . Table I I l i s t s seven sources of information from which D^, values may be drawn. From t h i s , i t i s seen that, i f there i s a v a i l a b l e an ADI (Acceptable D a i l y Intake) value o r i g i n a t i n g with the World Health Organization (_7), then that f i g u r e should be used as D^. A second e x c e l l e n t , but l i m i t e d , source of information i s the l i s t i n the N a t i o n a l Interim Primary Drinking Water Regul a t i o n s ; i t s MCL (Maximum Concentration Level) values (8) are d i r e c t l y c o n v e r t i b l e to L\j, values (1,2,3) by applying the f a c t o r weight of water consumed -3- body weight: D
T
= MCL/35
A t h i r d g e n e r a l l y accepted source of values i s the c o l l e c t i o n of TLVs (Threshold L i m i t Values) published by the American Conference of Governmental I n d u s t r i a l H y g i e n i s t s (9) and u t i l i z e d by the Occupational Safety and Health A d m i n i s t r a t i o n . Conversion of these to Dtp (10) i n v o l v e s three f a c t o r s : The f i r s t i s d i v i s i o n by 7/5 (= 1.4) to convert from a normal 5-day workweek to a 7-day exposure week. The second i s d i v i s i o n by 100; t h i s allows f o r e x c e p t i o n a l l y s e n s i t i v e i n d i v i d u a l s , who would not normally be part of the work f o r c e , and takes i n t o c o n s i d e r a t i o n the completely i n v o l u n t a r y and unsuspected nature of the exposure. The t h i r d f a c t o r converts from TLV (expressed i n mg m"~^) to a t o t a l dose; the breathing r a t e , RB', f o r a 70-kg person (BW = body weight) doing l i g h t work i s taken as 12.1 m /8-hr day (10) . Thus, 3
D
/
T
= (TLV x RB )/(140 x BW)
= TLV/810
TLVs must be used c a u t i o u s l y to preclude the e f f e c t s of hidden, i n a p p l i c a b l e assumptions• A f o u r t h o f f i c i a l source of values i s the Food and Drug A d m i n i s t r a t i o n , whose g u i d e l i n e s f i n d o c c a s i o n a l use i n d e r i v i n g PPLVs. For example, f o r a given compound, where the g u i d e l i n e i s f o r c o n c e n t r a t i o n i n beef f a t , D
T
_ (Meat consumption r a t e ) ( F r a c t i o n f a t i n meat)(guideline BW
value)
The remaining l i s t e d sources from which Dtp might be derived i n v o l v e animal experiments. Although s i m i l a r experiments were the u l t i m a t e source of the f i r s t four methods f o r c a l c u l a t i n g
14.
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269
Table I I . Information Sources from which to Derive Values of Acceptable D a i l y Doses ( D s ) of Toxic P o l l u t a n t s f o r Human Beings ( i n Order of P r i o r i t y ) T
Input
Information
Existing
Calculation Required
Reference
Standards None
WHO (7)
Maximum c o n c e n t r a t i o n l e v e l (MCL) i n d r i n k ing water
Adjust f o r water consumption l e v e l
EPA (8)
Threshold l i m i t value (TLV) f o r occupational exposures
Use f a c t o r s f o r breathing r a t e , exposure time, s a f e t y f a c t o r ,of 10r 2
ACGIH (9,10)
FDA g u i d e l i n e s f o r concentrations i n foods
Use f a c t o r s f o r consumption of p a r t i c u l a r foods
FDA
Acceptable (ADI)
d a i l y intake
Experimental
Results i n Laboratory Animal Studies
Lifetime no-effect l e v e l (NEL )
Use s a f e t y f a c t o r of 10~
(11)
Ninety-day n o - e f f e c t level (NEL )
Use safety 10'-3
(11)
Acute t o x i c i t y ( L D ^ Q )
Use s a f e t y f a c t o r of 1.155 x 10~
L
9Q
2
o
f a c t o r of
5
(1,2,3)
FATE OF CHEMICALS IN
270
THE
ENVIRONMENT
Dm, the t o x i c o l o g i c a l experiments r e f e r r e d to here have not gone through the process of e x t r a p o l a t i o n , e v a l u a t i o n , and consensus. Thus, they are used only i n the absence of b e t t e r data. The n o - e f f e c t l e v e l (NEL) from a chronic or l i f e t i m e study i n a l a b o r a t o r y animal i s diminished by a f a c t o r of 100 (11), i . e . , Drp = NEL x 10"*"
2
L
_ o
The widely accepted s a f e t y margin of 10 should be s u f f i c i e n t to allow f o r i n t e r s p e c i e s d i f f e r e n c e s and e s p e c i a l l y s u s c e p t i b l e i n d i v i d u a l s or groups w i t h i n the population. The n o - e f f e c t l e v e l from a subchronic (90-day) study i s assigned an a d d i t i o n a l s a f e t y f a c t o r of 10 because of the shorter period of exposure ( 1 1 ) . Hence
D
T
= NELgo x IO"
3
The most l i k e l y t o x i c i t y value to be found i n the l i t e r a ture i s the L D Q (dose l e t h a l to 50% of the animals) f o r some l a b o r a t o r y s p e c i e s , u s u a l l y rat or mouse. This value may be obtained by p l o t t i n g on p r o b i t paper the f r a c t i o n of e x p e r i mental animals k i l l e d against the acute dosage. There i s seldom enough information to permit e x t r a p o l a t i o n to a dosage at which only a very small (e.g., 1%) f r a c t i o n of the animals would be k i l l e d , much l e s s to an acceptable r i s k l e v e l . Handy and Schindler (12), however, assume a safe l i m i t f o r the maximum body concentration of a t o x i c substance to be 5 x 10 x IAJQ* Based on experimental s t u d i e s , they a l s o assume a b i o l o g i c a l h a l f - l i f e of 30 days, which implies a disappearance rate of 2.31% per day. If the d a i l y intake of the t o x i c substance i s made equal to the d a i l y disappearance rate at the safe concent r a t i o n l i m i t , then that safe concentration i s maintained. Thus, 5
D
T
= 2.31
x 10"
2
4
x 5 x IO"* x L D
5 Q
= 1.155
5
x 10"*
x LD
5 Q
This i s the l e a s t d e s i r a b l e method of estimating D but may be the only a v a i l a b l e method when new or r e l a t i v e l y u n f a m i l i a r compounds are being d e a l t with. Carcinogens pose a s p e c i a l challenge; although c h a r a c t e r i z a t i o n of c e r t a i n compounds as suspected carcinogens might be agreed upon by most researchers, there i s no consensus among s c i e n t i s t s regarding a s u i t a b l e mathematical model for c a r c i n o genesis; n e i t h e r i s there an accepted " s a f e " l e v e l f o r a c a r cinogen. For the time being, the authors regard a r i s k l e v e l of one cancer death per hundred thousand l i f e t i m e exposures to be an acceptable c r i t e r i o n f o r carcinogenic p o l l u t a n t s that do not threaten a l a r g e population. Such c r i t e r i a have been published by the U.S. Environmental P r o t e c t i o n Agency for d r i n k i n g water p o l l u t a n t s (13). T
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271
Coefficients
Assume that between any two adjacent media (such as s o i l and water or water and crops) the p o l l u t a n t Is p a r t i t i o n e d i n a p e r f e c t l y constant manner, e.g., C = Acceptable c o n c e n t r a t i o n i n s o i l C = K g C = Acceptable concentration i n water Cp = K^pC = Acceptable c o n c e n t r a t i o n i n p l a n t ( s ) , d r y weight b a s i s C = Kp Cp = Acceptable c o n c e n t r a t i o n i n meat animal g
w
W
g
w
a
a
Also, C
K
C
p ~ sp s
K
K
C
~ sw wp s
The K values are p a r t i t i o n c o e f f i c i e n t s . The assumption that these are r e a l constants i s seldom completely t r u e , of course, because e q u i l i b r i u m i s r a r e l y achieved and because the e q u i l i b r i u m r a t i o s g e n e r a l l y are not the same f o r a l l concent r a t i o n l e v e l s . Moreover, i t i s d i f f i c u l t to f i n d the needed i n f o r m a t i o n , and one must o f t e n accept a s i n g l e l i t e r a t u r e value as t y p i c a l of a given intermedia t r a n s f e r . When the organic content of the s o i l i s known or can be a c c u r a t e l y estimated, one can u s u a l l y d e r i v e K from a compound's aqueous s o l u b i l i t y , S, or i t s octanol/water p a r t i t i o n c o e f f i c i e n t , K ( 1 4 ) . Values of Kp , namely " b i o c o n c e n t r a t i o n f a c t o r s " between feed and meat animals ( 15,16), can a l s o be derived from S or K . Bioconcent r a t i o n f a c t o r s between water and f i s h are w e l l documented (14)• A c o n s i d e r a b l e weakness e x i s t s i n our perception of the proper estimates to use f o r p a r t i t i o n c o e f f i c i e n t s between s o i l and e d i b l e crop m a t e r i a l s . Thus, at one time, two of the present authors used a d e f a u l t value of K = 1 f o r munitions compounds that are n e i t h e r very s o l u b l e i n water nor very i n s o l u b l e (4_); a t another time, a value of was assumed f o r compounds with very low values of K , i . e . , polybromobiphenyls (6). g w
Q W
a
Q W
g p
eTT
Scenarios, Single Pathway PPLVs (SPPPLVs), and PPLVs For each category of land or water body use, one may e n v i s i o n a s i m p l i f i e d s c e n a r i o . In each s c e n a r i o , only those a c t i v i t i e s most l i k e l y to lead to t o x i c exposures are considered. For example, i n the i n d u s t r i a l s c e n a r i o , indoor workers would not be exposed to l e v e l s of dust bearing high concentrations of s o i l contaminants; outdoor workers who s t i r up dry s o i l with heavy machinery, however, could expect to i n h a l e contaminant-laden d u s t . A scenario could i n v o l v e more than one exposure pathway. Thus, the i n d u s t r i a l worker might d r i n k water from a contaminated w e l l , i n a d d i t i o n to breathing contaminated dust; these exposures might represent not only d i f f e r e n t pathways but d i f f e r e n t sources.
FATE OF CHEMICALS
272
IN THE ENVIRONMENT
An SPPPLV u s u a l l y i n v o l v e s 1^, one or more K v a l u e s , and a rate of i n g e s t i o n , i n h a l a t i o n , or other contaminant t r a n s f e r f a c t o r . A d d i t i o n a l f a c t o r s may be i n c l u d e d to account f o r e f f e c t s that modify i n t e n s i t y or time of exposure. Examples of general equations of t h i s sort have been published p r e v i o u s l y (1,2,3); those u s e f u l i n the present examples have been modified as r e q u i r e d . Where pathways have t h e i r o r i g i n i n the same medium or have a common point of i n t e r s e c t i o n , a simple c a l c u l a t i o n i s used to a d j u s t the c o n c e n t r a t i o n a t the o r i g i n or the i n t e r s e c t i o n such that SPPPLVs taken together provide the target organism, u s u a l l y humans, with an exposure p r o v i d i n g e x a c t l y D^. Thus, f o r SPPPLVs v i a three pathways from the same source: PPLV = [ l / ( S P P P L V )
1
+ l/(SPPPLV)
2
+
l/(SPPPLV)3]"
1
If s e v e r a l independent sources of the p o l l u t a n t have to be c o n s i d e r e d , the i n d i v i d u a l l y c a l c u l a t e d PPLVs must be reduced to some a r b i t r a r y combination c o n s i s t e n t with the Drj,. Physicochemical P r o p e r t i e s For the s t u d i e s summarized i n Table I and discussed i n the f o l l o w i n g s e c t i o n s of the t e x t , physicochemical p r o p e r t i e s ( i n c l u d i n g p a r t i t i o n c o e f f i c i e n t s ) were c o l l e c t e d from a v a r i e t y of reference documents or estimated according to a v a i l a b l e equations (Table I I I ) • Acceptable d a i l y doses were c a l c u l a t e d from t o x i c o l o g i c a l data (Table I I I ) • When more than one equation was a v a i l a b l e , judgment was used to determine which to apply. Table I I I excludes those contaminants footnoted i n Table I . A d e f a u l t value of 1.0 was adopted f o r K f o r the f i r s t nine compounds of Table I I I ( 4 ) . For PBBs, the value of log K was c a l c u l a t e d from the s o l u b i l i t y i n creek water (7.96 x 10~ yM), according to the equation ( 1 , 3 ) : Q C
4
log
K
o c
= -0.557 l o g S + 4.277 = 6.003
With an assumed 2% organic carbon content i n s o i l , K = 5 x IO" f o r PBBs; i f i s assumed to be 5, K = K x K^p = 2.5 x 10 . g w
5
g p
g w
Alabama Army Ammunition Plant (4) The 5,168-acre Alabama Army Ammunition Plant t r a c t , on the banks of the Coosa River i n T a l l a d e g a County, AL, i s 4 miles north of C h i l d e r s b u r g , AL ( 4 ) . Plant o p e r a t i o n s , between 1942 and 1945, l e f t residues from the manufacture of diphenylamine, TNT, DNT, and t e t r y l . Some of these compounds have been found on the s i t e , and others are suspected. The shallow water t a b l e , d r a i n i n g to the Coosa R i v e r , i s probably contaminated, but only deeper, uncontaminated a q u i f e r s would be used as the source f o r
14.
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273
Table I I I . Physicochemical Constants and Acceptable D a i l y Doses ( D ) of S o i l and Water Contaminants 3
T
Dmh S
Contaminant^
TNT DNT Tetryl TNB DNB Diphenylamine Aniline N,N-Diraethylaniline Nitrobenzene RDX PBBs PGDN a. b. c. d. e. f.
(mg/kg/ day)
e
k (day"" )
C
L
(mg/L)
K
124* 273 35 32 370 36° 1
n
1
1
35,000° 16,000° 1,780? 44 5xl0l,300 1
4 t
v
°§
2
1
1.84J 1.98
m
— 1.18
14.7
— —
6.7x10"•3 4.3x10"•3 1.4x20"•2 1.4x10"•2 3.6x10"•3 1.3x10"•2
— —
2.8x10"•4 4.4x10"-4
— —
9x10" -3
—
5.1 4.6
k
k
— m
— — — — — —
0.90
9.6
k
—
0.87^ w
BCFS
12.9
— —
k
— — —
3
1.4xl0" 3.2xl0" 1.8xl0" 5.8xl0~ 1.2xl0" 2.0xl0*"
1
— — — — —
4.2
5
3
3
3
1.2xl0"" 3.0xl0"
2
2
3
r
— 2.8
2
1
6.2xl0~ 1.0xl0" 3.73xl0" 2.5xl0"
3s
4u
4x
Only data u s e f u l f o r thepresent report are given here. See Table 1 f o r a b b r e v i a t i o n s . Solubility. Log octanol/water p a r t i t i o n c o e f f i c i e n t . Depuration rate constant f o r f i s h ( 1 7 ) . Basic data f o r equations presumably involve contaminant conc e n t r a t i o n s i n dry f e e d . Experiments were c a r r i e d out long enough f o r a steady c o n c e n t r a t i o n i n f a t to be reached f o r any concentration i n feed. K = BF x 0.3 f o r c a t t l e . For a l l c a l c u l a t e d values of BF shown i n t h i s t a b l e , the equation used i s l o g BF = 1.2-0.56 l o g S, (when S must be expressed i n mg/L) U5).
Table I I I continued on next page
274
FATE OF CHEMICALS IN THE ENVIRONMENT
Table I I I — c o n t i n u e d g. h.
BCF = Concentration i n whole f i s h / c o n c e n t r a t i o n In water. Dm = acceptable d a i l y dose, as discussed i n t e x t . Sources of D are provided f o r the f i r s t 9 compounds i n Reference ( 4 ) ; the value f o r DNT i s based on a c r i t e r i o n of one excess cancer death i n 10^ l i f e t i m e exposure. i. Reference ( 1 8 ) . j. C a l c u l a t e d from value f o r TNB (19) by method of Reference (14). k. Log k = 1.47-0.414 l o g K ; k i n day"" ( 1 7 ) . 1. Log BCF - 0.76 l o g K -0.3, from Reference ( 1 4 ) . ra. Reference ( 1 9 ) . n. Reference ( 2 0 ) . o. Reference ( 2 1 ) . p. Reference ( 1 5 ) . q. Reference ( 2 2 ) . r . Average value f o r 27-day studies (23). s. Reference ( 2 4 ) . t . For creek water; s o l u b i l i t y i n d i s t i l l e d water i s 9 times lower ( 2 5 ) . u. Based on FDA g u i d e l i n e of 0.3 mg/kg i n beef f a t (26), 30% f a t i n beef, and consumption of 0.29 kg/day, T
1
2
Q W
2
Q W
0.29 x 0.3 x 0.3
n
Dm =
-. -4 = 3.73 x 10 0
0
1A
mg/kg
v. w.
Reference ( 2 7 ) . Estimated according to Reference (14)•
x.
Estimated from TLV (9) of 0.2 mg/m according to equation in text.
D, T
3
= (Breathing r a t e f o r 8-hr work day)x(TLV)x(5 day work week) (Body weight)x(7 day work week)x(safety f a c t o r )
3 3 12.1 m x 5 days x 0.2 mg/m 70 kg x 7 days x 100
14.
ROSENBLATT E T AL.
Preliminary Pollutant Limit Value Process
275
water s u p p l i e s . Hence, groundwater contamination was not considered i n PPLV s c e n a r i o s . Consumption of l i v e s t o c k and d a i r y products, as w e l l as i n g e s t i o n of s o i l by c h i l d r e n , were considered f o r the subs i s t e n c e a g r i c u l t u r e case, but the SPPPLVs were s i g n i f i c a n t l y higher than f o r vegetable consumption; s i m i l a r l y , s o i l i n g e s t i o n by c h i l d r e n was considered f o r the r e s i d e n t i a l housing s c e n a r i o . For the subsistence farming and r e s i d e n t i a l housing s c e n a r i o s , the only s i g n i f i c a n t pathway f o r the nine organic compounds of concern would be that from s o i l v i a vegetable consumption. The SPPPLV (and a l s o , i n t h i s case, the PPLV) would be: BW x D
rj
= s
z Vegetable Consumption (dry weight) x 70 D_ = 953 D 0.0734 kg x 1 T
=
U
On the other hand, i f the land were to be used f o r a p a r t ment housing, the growing of s i g n i f i c a n t amounts of vegetables would not be expected. Here, the only s i g n i f i c a n t pathway was adjudged to be v i a i n g e s t i o n of s o i l by c h i l d r e n , with an estimated consumption of 0.1 g ( I O kg), per 12-kg c h i l d per day. The pathway-related equation f o r t h i s s i t u a t i o n i s : - 4
C
= S
7- = 1.2 x 10
10~
D
m
4
For the i n d u s t r i a l s e t t i n g , the outdoor worker s c e n a r i o , as mentioned above, represents a worst case. Owing to wind and weather c o n d i t i o n s , one assumes that the worker i s exposed to dust only 50% of h i s approximately 225 workdays. The maximum dust c o n c e n t r a t i o n i s the normal nuisance dust TLV (9) of 10""^ kg/m , breathed by a 70-kg adult at a rate of 12.1 n ? per 8-hour workday (_4). A f a c t o r of 10 i s introduced (see equation below) to account f o r a more robust worker population than the general p o p u l a t i o n . From these assumptions, the c a l c u l a t i o n i s 3
C
=
365 x 70 x 10 x D _ = i = 2.35 x 10 D 10" x 225 x 0.4 x 12.1 D
1
For DNT, an oncogen, the f a c t o r of 10 i s i n a p p r o p r i a t e , so that C
6
s
- 2.35 x 10 Dm
FATE OF CHEMICALS IN THE ENVIRONMENT
276
Timber-harvesting might involve perhaps 4% of the exposure to dust posed by other outdoor i n d u s t r i a l a c t i v i t y ; hence, the values of C would be higher by a f a c t o r of 25. Ingestion of venison taken i n hunting a c t i v i t y i s assumed to be 11 kg by each member of a f a m i l y of four per year. The value of K i s adjusted by a f a c t o r of 2/3, because venison i s a leaner meat, perhaps 20% f a t , than beef. The animals browse over a wide area, i n c l u d i n g uncontaminated land, f o r which reason a f a c t o r of 0.1 i s introduced. The equation thus derived (with BW = 70) i s g
C
70 x 365 x D , = Tr-: , „ — r r - = 3.48 x 10 D^/K s 0.1 x (2/3) K x l l T p a pa o
/
o
N
Results f o r the f i v e scenarios examined i n d e t a i l are shown i n Table IV. It may be seen that subsistence farming and r e s i d e n t i a l housing e n t a i l the most r e s t r i c t i v e PPLVs at the Alabama AAP s i t e . Savanna Army Depot A c t i v i t y
(5)
The 5,330 hectare (13,170 acre) Savanna Army Depot A c t i v i t y , north of Savanna, IL, c o n s i s t s of high ground and M i s s i s s i p p i River f l o o d p l a i n . In the f l o o d p l a i n are 223 hectares of waterways connected to the r i v e r ; about 10 hectares of sediment p l a i n i n these waterways are considered p o t e n t i a l l y contaminated by m u n i t i o n s - r e l a t e d compounds (see Table I ) . Of these compounds, only TNT has been i s o l a t e d (0.3 rag/kg i n one sediment sample); DNT, TNB, and RDX are a s s o c i a t e d with TNT i n other munitions contexts, hence they were a l s o i n c l u d e d . The waterways are f i s h e d by a number of a c t i v i t y personnel and r e t i r e e s . These persons and t h e i r f a m i l i e s may eat some of t h e i r c a t c h , and thereby ingest those compounds that might be present i n the f i s h (predominantly carp and c a t f i s h , both bottomfeeders) • Acceptable safe sediment l e v e l guidance f o r these compounds was therefore d e s i r e d . The a c t i v i t y a l s o has s i x bermed dry lagoons whose t o t a l area comprises 0.521 h e c t a r e s . RDX has been found i n surface s o i l s of lagoons on high ground at l e v e l s up to 4,000 mg/kg. TNT and TNB have been found i n groundwater beneath these h i g h ground lagoons at concentrations below 0.5 rag/L, and could be assumed to r e s i d e i n lagoon s o i l , as could DNT. This groundwater i s d i r e c t e d to the M i s s i s s i p p i R i v e r . There was concern that the leachate from the lagoons could pose a hazard i n r i v e r derived water s u p p l i e s downstream. The question of acceptable s o i l l e v e l s i n waterway s e d i ments was resolved by l i n k i n g such l e v e l s to the human exposure route of f i s h i n g e s t i o n . The fishermen involved do not r e q u i r e the f i s h they catch to provide a major p o r t i o n of t h e i r d i e t . Thus, a s a f e - s i d e d estimate of t h e i r f i s h d i e t a r y intake was set
14.
ROSENBLATT E T AL.
Preliminary Pollutant Limit Value Process
277
Table IV. Allowable Concentrations (PPLVs) f o r S o i l Contaminants a t Alabama Army Ammunition Plant
Pathways Governing PPLV
PPLV f o r S o i l ( C ) mg/kg)
Subsistence farming
Vegetable consumption
953 Dm
Residential housing
Vegetable
953 Dm
Apartment housing
S o i l i n g e s t i o n by children
1.2X1CT Dry
Industrial (outdoor worker)
Dust
2.35xl0'p, (2.35xl0 D
Hunting
Consumption of venison
Scenario
consumption
inhalation
g
6 T
3.48
x 10
T
f o r DNT) D
T
K pa
Timber harvesting
Dust
inhalation
8
5.9xl0 D ( 5 . 9 x l 0 f o r DNT) T
7
FATE OF CHEMICALS IN THE ENVIRONMENT
278
at 0.01 kg per 70 kg person per day. T h i s i s about 1.5 times as high as the i n g e s t i o n rate employed i n Water Q u a l i t y C r i t e r i a computations (13). Factors r e l a t e d to the p a t t e r n of intake by f i s h of the compounds of concern were i n t r o d u c e d . These were: (1) The r a t i o of contaminated waterway bottom a r e a / t o t a l waterway bottom area; (2) consumption by bottom feeders of d e t r i t u s , i . e . , 6% of t h e i r body weight (28); and (3) the depuration rate constants, k , of Table I I I . Based on these, 2
70 x 223 x k C
s°
x D
?
, ?
0.06x10x0.01
• "
6
X
1 0
k
2
°T
C a l c u l a t e d values of C are shown i n Table V. The C value for TNT ( 1 . 9 x l 0 mg/kg) i s w e l l i n excess of the c o n c e n t r a t i o n of TNT i n the one measured sediment sample (0.3 mg/kg). It was expected that the C l e v e l s f o r other postulated compounds of concern would a l s o be f a r i n excess of sediment l e v e l s . For leaching from lagoons, water consumption was considered the route of p o s s i b l e exposure to the p o l l u t a n t s . Estimated acceptable d r i n k i n g water l e v e l s were determined by g
g
4
g
BW x D C
w
=
70 D
2 L/day/person
=
=
3 5
D
T
n
< «
/ L )
The c o n c e n t r a t i o n that could p o s s i b l y be a t t a i n e d i n the r i v e r due to contaminated dry lagoon s o i l ( C ) was then c a l c u l a t e d . A worst-case scenario f o r d e l i v e r y of p o l l u t a n t to the M i s s i s s i p p i River would e n t a i l the assumptions t h a t : (1) The r a i n f a l l on a l l lagoons becomes saturated with the contaminant; (2) a l l contaminated rainwater reaches the r i v e r , and (3) chara c t e r i s t i c r i v e r flow i s at an h i s t o r i c low. Hence, the s o i l contamination l e v e l s do not enter i n t o c o n s i d e r a t i o n , only the lagoon areas exposed to r a i n f a l l . Annual r a i n f a l l i n the v i c i n i t y of the A c t i v i t y i s 0.86 m/year. The h i s t o r i c low flow of the M i s s i s s i p p i River i n the A c t i v i t y area was estimated at 2 . 5 x l 0 L / y r . Thus, w
1 3
C ' = I^S w
0 0
"
8
area x R a i n f a l l
H i s t o r i c low
flow
I n s e r t i o n of values f o r area, r a i n , and a consistent unit b a s i s , yields cJ
= 1.79
x 10"
7
x S
r i v e r flow,converted
x S (mg/L)
The r a t i o C / C may be considered a " s a f e t y f a c t o r ; " i f i n excess of 1, i t would i n d i c a t e that the acceptable d r i n k i n g w
w
to
14.
ROSENBLATT E T AL.
Preliminary Pollutant Limit Value Process
Table V. C a l c u l a t e d Values of Acceptable Contaminant Levels i n Waterway Sediment ( C ) and Safety Factors ( C / C ' ) f o r River-Derived Drinking Water, Savanna Army Depot A c t i v i t y . (Based on Data of Table I I I ; f o r c a l c u l a t i o n , see text) g
w
Contaminant
(mg/kg)
TNT DNT TNB RDX
1.9xl0
4
w
%l
2.3xl0 1.9X10 3.5xl0 4.5xl0
3
1
4
3
279
FATE OF CHEMICALS IN
280
THE
ENVIRONMENT
water concentrations would exceed the r i v e r contamination l e v e l s for t h i s worst-case s c e n a r i o . This r a t i o , i n terms of Dm and S, is C / C ' = 1.95 w
w
x 10
8
x
D /S T
Values of C / C f o r p o s s i b l e compounds of concern appear i n Table V. A l l values are w e l l i n excess of 1, which i n d i c a t e s that downstream d r i n k i n g water supplies would not reach p o l l u t ant l e v e l s that might cause adverse human h e a l t h e f f e c t s • w
w
G r a t i o t County L a n d f i l l
(_6)
Approximately 122,000 kg of polybromobiphenyls (PBBs) were buried i n the 40-acre G r a t i o t County, MI, l a n d f i l l between 1971 and 1973. The upper n a t u r a l c l a y b a r r i e r beneath the l a n d f i l l was breached i n a few l o c a t i o n s ; hence, groundwater flowing beneath the l a n d f i l l can become contaminated as a r e s u l t of f l o o d i n g of the l a n d f i l l during periods when the groundwater s i g n i f i c a n t l y r i s e s , even i f capping l a r g e l y prevents leaching by rainwater f a l l i n g on the s i t e . In a d d i t i o n to the l a n d f i l l , adjacent farms seem to have been contaminated by PBBs that may have blown o f f trucks c a r r y i n g such m a t e r i a l to the l a n d f i l l . Although the s o l u b i l i t y of PBBs, measured i n d i s t i l l e d , deionized or creek water, i s below 10"" mg/L, groundwater concentrat i o n s of up to 2.6 x 10" mg/L have been reported; t h i s i s not s u r p r i s i n g , since d i s s o l v e d organic matter can g r e a t l y increase the s o l u b i l i t y of PBBs (25) • Three land use scenarios have been examined (see Table I ) ; a l l r e s t on the assumption that the PBBs w i l l not be removed and that the l a n d f i l l w i l l be p r o p e r l y capped. Other s c e n a r i o s , i n which PBB removal down to a safe l e v e l was p o s t u l a t e d , could be developed, and t h e i r consequences explored. The t r a n s f e r of PBBs from s o i l to plants i s so low, e.g., Table I I I and References (6,29), that the only important i s s u e i n the a g r i c u l t u r a l scenario appears to be s o i l i n g e s t i o n (and p o s s i b l y i n g e s t i o n of groundwater) by c a t t l e . Based on an e s t i mated h a l f - l i f e , t w , i n beef of 120 days (30) an estimated mass of f a t per animal, M^, of 67 kg and a s o i l i n g e s t i o n r a t e , M , of 0.72 kg/day (31), a reasonably conservative s o i l - t o - f a t b i o c o n c e n t r a t i o n f a c t o r can be obtained: 3
2
2
g
BF
=
s
0.72
x t
—
^
M
f
1
/
2
,f\r%—
"
1
»86
x 0.693
Where C = FDA g u i d e l i n e f o r PBB concentration SPPPLV f o r the s o i l i n g e s t i o n pathway i s then f
C
s
= C /BF f
S
= 0.3/1.86 = 0.16
mg/kg
i n f a t (26),
the
14.
Preliminary Pollutant Limit Value Process
ROSENBLATT E T AL.
281
Note: Should groundwater (45.4 kg/day) be used f o r c a t t l e , the a p p l i c a b l e PPLV would be C c
-
x M x 0.693 / » = 2.6 x 10 mg/L 45.4 x t ^
f
f
/c
&
w
2
If residences are supplied with well water, t h i s would be the most l i k e l y source of PBBs. For a d u l t s , the acceptable c o n c e n t r a t i o n would be C = 35 Dj = 1.3 x 10 mg/L. (That f o r c h i l d r e n might be somewhat l e s s . ) The r e s i d e n t i a l s o i l c o n c e n t r a t i o n PPLV i s governed by c h i l d r e n ' s s o i l i n g e s t i o n , estimated at IO"" kg/day ( 3 2 ) . w
4
r s C
B W
=
X
D
child T =4 10
1
=
2
k
X
S ~^4 10
P
T =
4
4
5
m
g
/
k
g
kg/day
I f one source i s assumed to be contaminated at l e s s than i t s a p p l i c a b l e PPLV, then the PPLV f o r the other source need not be reduced to zero. Thus, i f the groundwater were contaminated by 0.005 mg/L of PBBs, the r e s i d e n t i a l s o i l PPLV, C , would be (0.008/0.013) x 45 - 28 mg/kg. The PPLVs a p p l i c a b l e to i n d u s t r i a l scenarios would p o s s i b l y be water i n g e s t i o n (as i n the case of r e s i d e n t i a l housing), and more l i k e l y dust i n h a l a t i o n . A conservative approach would be to use the equation a p p l i e d to DNT f o r worker exposure to dust, i.e., g
C
6
s
= 2.35 x 10 D
T
= 875 mg/kg
In view of the above, groundwater i n the v i c i n i t y of the l a n d f i l l should be used as a d r i n k i n g water supply only i f the PBB concentrations are v i g o r o u s l y monitored. C a t t l e grazing should be r e s t r i c t e d to the extent necessary. Bangor Naval Submarine Base Bangor Naval Submarine Base, on the Hood Canal i n the State of Washington, provides f i n e r e c r e a t i o n a l f a c i l i t i e s f o r s e r v i c e people s t a t i o n e d there, as w e l l as f o r c i v i l i a n employees. A proposal to d i v e r t runoff from munitions-contaminated areas towards the r e c r e a t i o n a l f i s h i n g pond, C a t t a i l Lake, l e d to a d e c i s i o n to i d e n t i f y hazard l e v e l s f o r the compounds of i n t e r e s t . In a d d i t i o n to t r o u t , there was concern over contamination of b i v a l v e s , such as o y s t e r s , c o c k l e s , and clams, a t the pond's o u t l e t to Hood Canal. B i o c o n c e n t r a t i o n f a c t o r s (BCFs), assumed a p p l i c a b l e f o r both f i s h and b i v a l v e s , were developed f o r three compounds (Table I I I ) . BCFs, together with D™ values and worstcase l e v e l s of f i s h or b i v a l v e consumption (0.4 kg/day) provided PPLVs f o r the pond water, according to the equation
FATE OF CHEMICALS IN THE ENVIRONMENT
282
BW °w
=
X
D
T
=
Consumption rate x BCF
1
7
5
D
T
/
B
C
F
From t h i s equation, C values were c a l c u l a t e d , i n mg/L, a s : TNT, 1.7 x 10" ; RDX, 4.2 x IO" ; PGDN, 1.6 x I O " . These very s t r i n g e n t values r e f l e c t the l i f e t i m e consumption of almost a pound of f i s h per person per day, and do not take into account the f a c t that whole f i s h g e n e r a l l y c o n t a i n more f a t than the e d i b l e portions of f i s h or b i v a l v e s ; the BCFs r e f l e c t whole f i s h d a t a . I t i s recommended that the foregoing C^ values be used as d e t e c t i o n l i m i t s f o r monitoring. I f these are exceeded, the assumptions may need to be reconsidered, since they appear to be somewhat too s t r i n g e n t . w
2
2
2
Summary The examples provided above represent a v a r i e t y of s i t u a t i o n s where the uses to which land or water may be put would depend on estimates of acceptable contaminant l e v e l s . Conversely, contaminants might be removed from land or prevented from reaching water so that the land or water could be used b e n e f i c i a l l y f o r s p e c i f i e d purposes. Literature 1.
2. 3.
4.
5.
Cited
Rosenblatt, D.H.; Dacre, J.C.; Cogley, D.R. "An Environmental Fate Model Leading to P r e l i m i n a r y P o l l u t a n t L i m i t Values f o r Human Health E f f e c t s , " T e c h n i c a l Report 8005, U.S. Army Medical Bioengineering Research and Development Laboratory, Fort D e t r i c k , F r e d e r i c k , MD, 1980, AD B049917L. Dacre, J.C.; Rosenblatt, D.H.; COgley, D.R. E n v i r o n . Sci. Technol. 1980, 14, 778-784. Rosenblatt, D.H.; Dacre, J.C.; Cogley, D.R. "Environmental Risk A n a l y s i s f o r Chemicals"; Conway, R.A., Ed.; Van Nostrand Reinhold: New York, 1982, Chapter 15. Rosenblatt, D.H.; Small, M.J. " P r e l i m i n a r y P o l l u t a n t L i m i t Values f o r Alabama Army Ammunition P l a n t , " T e c h n i c a l Report 8105, U.S. Army Medical Bioengineering Research and Development Laboratory, Fort D e t r i c k , F r e d e r i c k , MD, August 1981, AD A104203. Rosenblatt, D.H. "Environmental Risk Assessment f o r Four M u n i t i o n s - r e l a t e d Contaminants at Savanna Army Depot A c t i v i t y , " T e c h n i c a l Report 8110, U.S. Army Medical Bioengineering Research and Development Laboratory, Fort D e t r i c k , F r e d e r i c k , MD, November 1981, AD A116650.
14. 6.
7.
8.
9.
10.
11.
12.
13.
14.
15. 16. 17.
17.
19.
20.
ROSENBLATT E T AL.
Preliminary Pollutant Limit Value Process
283
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R E C E I V E D April 15, 1983.
