Bull. Environ. Contam. Toxicol. (1985) 35:51-60 9 1985 Springer-Verlag New York Inc.

~E n v i r o n m e n t a l Contamination i a n d Toxicology

Quantification and Distribution of Polychlorinated Biphenyls in Farm Silos 1 L. B. Willett, 1 Ting-Ting Y. Liu, 1 Holly I. Durst, ~ Burton D. Cardwell, 2 and Edwin D. Renkie 2 ~Department of Dairy Science, Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH 44691 and ZToxic Substances and Emergency Services Office, Michigan Department of Agriculture, P.O. Box 30017, Lansing, MI 48909 One source of p o l y c h l o r i n a t e d b i p h e n y l s (PCBs) in the human food chain has been c o n c r e t e stave farm silos that were treated with a coating m a t e r i a l called Cumar (Willett and Hess, 1975; Willett, 1980). This coating was formulated in 1941 to aid the proper curing of c o n c r e t e and p r o t e c t the staves and joint mortar from the erosive actions of the organic acids which are p r o d u c e d during f e r m e n t a t i o n of silage. W i l l e t t and Hess (1975) reported that Cumar c o n t a i n e d a p p r o x i m a t e l y 19% Aroclor 1254, a PCB m i x t u r e , and 5.4% Aroclor 5460, a m i x t u r e of p o l y c h l o r i n a t e d terphenyls. Once applied to the silo wall, and the carrier s o l v e n t s evaporated, the c~red coating c o n t a i n e d 32.6% PCB. Typically, 2.45 m of silo wall were covered per liter. Thus, in the case of a f r e s h l y coated silo, if comp l e t e l y coated, the c o n c e n t r a t i o n of Aroclor 1254 equaled 467 ppm on a w h o l e silo basis. If coated only on joint mortar, a f r e q u e n t l y used procedure, the c o n c e n t r a t i o n e q u a l e d 109 ppm. The PCB c o n t e n t of silos d e c l i n e d with use as the coating d i s i n t e g r a t e d and flaked off the silo wall. Studies have r e v e a l e d that the PCBs were soluble in the organic acids, including lactic and acetic, that were p r o d u c e d d u r i n g the f e r m e n t a t i o n process. Once d i s s o l v e d in these acids, the residues d i f f u s e d toward the center and leached toward the b o t t o m of the silo (Willett, 1974). A c c o r d i n g to the "Toxic Substances Control Act of 1979", m a t e r i a l s which c o n t a i n more than 50 ~g/g of PCBs require special h a n d l i n g and disposal. Usually, s c r a p i n g s are taken from the surface of silos to d e t e r m i n e if a silo is c o n t a m i n a t e d . The c o n c e n t r a t i o n of PCB in s c r a p i n g s g e n e r a l l y exceeds the 50 ~[g/g limit. However, s c r a p i n g s r e p r e s e n t only the c o n c e n tration of PCBs d i r e c t l y on the inner surface of the silo and are not r e p r e s e n t a t i v e of the entire structure.

51

In order to d e t e r m i n e the r e l a t i o n s h i p b e t w e e n the conc e n t r a t i o n of PCBs in s c r a p i n g s from the silo wall and the c o n c e n t r a t i o n in the e n t i r e s t r u c t u r e a s t u d y was c o n d u c t e d to d e t e r m i n e the e x t e n t of p e n e t r a t i o n of PCBs into c o n c r e t e silo s t a v e s , and d e v e l o p e q u a t i o n s w h e r e b y the c o n c e n t r a t i o n of PCBs in the e n t i r e silo can be p r e d i c t e d from the c o n c e n t r a t i o n of PCBs in s c r a p i n g s from the inner silo s u r f a c e . MATERIALS

AND

METHODS

Silo s t a v e s from M i c h i g a n and Ohio, k n o w n to be cont a m i n a t e d w i t h p o l y c h l o r i n a t e d b i p h e n y l s , w e r e coll e c t e d to d e t e r m i n e the d e p t h of p e n e t r a t i o n of PCB residues. Staves used in this s t u d y were m a n u f a c t u r e d b y N a t i o n a l , C & B, I n t e r l o c k e n and M i c h i g a n Silo C o m p a n i e s and i n c l u d e d both p l a i n - and w a x e d - s t a v e c o n s t r u c t i o n from the l a t t e r m a n u f a c t u r e r . Staves r e p r e s e n t e d silos of v a r i o u s c o n d i t i o n s , from t h o s e w i t h C u m a r c o a t i n g intact to t h o s e c l e a n e d and recoated. A b r i e f d e s c r i p t i o n of the s t a v e s is in T a b l e i. Silo s t a v e s w e r e w e i g h e d and m e a s u r e d , and their c o n d i tion and h i s t o r y r e c o r d e d . F i v e l o c a t i o n s were sel e c t e d in each full s t a v e for s a m p l i n g , p o s i t i o n s A-E (Figure i). P o s i t i o n s r e p r e s e n t e d b o t h edge and c e n t e r locations. Each s a m p l e p o s i t i o n was cut in four to six c r o s s - s e c t i o n s t h r o u g h the s t a v e on a m a s o n r y saw w i t h a diamond blade. The size and w e i g h t of s e c t i o n s w e r e r e c o r d e d w i t h each a p p r o x i m a t e l y 25 x 25 mm on the face and 10 mm thick. Sections were labeled consecutively w i t h 1 d e s i g n a t i n g the i n s i d e s u r f a c e . Sections were a l s o cut from a c o n t r o l s t a v e to m o n i t o r m e t h o d c r o s s contamination. S e c t i o n s w e r e g e n t l y rinsed, and air d r i e d to r e m o v e r e s i d u a l d u s t from c u t t i n g . S e c t i o n s w e r e c r u s h e d in a m o r t a r and p e s t l e to a p p r o x i m a t e l y 1 mm in d i a m e t e r . Crushed sections were ground (20,000 rpm for 2.5 min.) to a fine p o w d e r in a m i l l e q u i p p e d with a t u n g s t e n c a r b i d e b l a d e (A-20 U n i v e r s a l Mill, T e k m a r C o m p a n y , C i n c i n n a t i , OH). To p r e v e n t cross-contamination, s e c t i o n w e r e g r o u n d by d e s c e n d i n g s a m p l e n u m b e r and 5-7 g r a m s of a b s o r b a n t c l a y was ground between sections. S u r f a c e s of the m i l l , m o r t a r and p e s t l e w e r e c l e a n e d w i t h a c e t o n e b e t w e e n s a m p l e s . B l a n k s w e r e g r o u n d p r i o r to each stave. In a d d i t i o n s c r a p i n g s were taken from the i n s i d e s u r f a c e a d j a c e n t to the s a m p l i n g sites. S c r a p i n g t h i c k n e s s was influe n c e d by d e n s i t y and c o n d i t i o n of the s t a v e s u r f a c e . S c r a p i n g t h i c k n e s s r a n g e d from .01 to 1.5 mm. Two g r a m s a m p l e s of the g r o u n d s e c t i o n s into tubes that had been p r e w a s h e d w i t h 52

were weighed t o l u e n e and

Table

i.

No.

Silo s t a v e s penetration

Appearance Condition

Brand

OM-I b

Michigan d

OM-2 b

Michigan d

OCB-I b

C & Bd

ON-1 b

National d

MM-I b

Michigan e

b

Michigan e

MM_3 b

Michigan e

MM_4 b

Michlgan

MM-2

used to d e t e r m i n e of PCBs.

e e

MM-5 b

Michlgan

MM_6 b

Michlgan

MM-7 c

Michlgan

MM-8 c

Michlgan

MM-9 c

Michlgan

MI-I c

Interlocken e

e e e e

&

Recoated, surface very good Recoated, surface very good Cumar coating intact, e x c e l l e n t PCB c o n t a i n i n g c o a t i n g intact, excellent Some e r o s i o n , good No e r o s i o n , excellent Recoated, coating & s u r f a c e poor Recoated, coating & surface poor Some e r o s i o n , surface v e r y g o o d B a d l y e r o d e d , poor condition Moderate surface e r o s i o n , fair Minor erosion, good Minor erosion, good Surface erosion, fair

~F i g u r e

io Entire stave available. C d P a r t l a l or b r o k e n s t a v e S o u r c e - Ohio. esource - Michigan.

the

available.

53

Positions a Sampled

A-E A-E A-E A-E

A-E A-E A-E A-E A-E A-F A-C D,E A-C A,B

Figure

i.

The cutting and on silo staves

sectioning

pattern

used

acetone. Samples were e x t r a c t e d with 9 ml of 2% benzene in p e t r o l e u m ether, agitated for 1 min, centrifuged at 1,240 x g for 3 min, and the s u p e r n a t a n t decanted into s i m i l a r l y p r e w a s h e d s c r e w - t o p vials. Samples were reextracted as above and the supernatants combined. Method recovery and q u a l i t y control were based on spiked control stave samples. Silo scrapings were extracted in the same m a n n e r using 9 ml of 2% b e n z e n e in p e t r o l e u m ether regardless of sample weight. ~ m p l e analysis was by g a s - l i q u i d - c h r o m a t o g r a p h using a Ni detector (5736-A Gas C h r o m a t o g r a p h , Hewlett Packard, Avondale, PA) . A 1.8 m glass column of 5% OV-101 on G a s - C h r o m Q (80/100 mesh) was used with A r g o n - M e t h a n e (95:5) as carrier and purge. Running c o n d i t i o n s were: oven 250~ d e t e c t o r 300~ and injection port 300~ Samples were diluted and injected to be within the linear d e t e c t i o n range of the EC-cell. Q u a n t i f i c a t i o n was based on e l e c t r o n i c a l l y integrated area of peaks 3-9 (Figure 2). RESULTS

AND D I S C U S S I O N

The procedures utilized in this study were adequate to r e l i a b l y d e t e r m i n e the p e n e t r a t i o n of p o l y c h l o r i n a t e d b i p h e n y l s into c o n c r e t e silo staves. R e c o v e r y of PCBs 54

I.

8 Figure

2.

Typical c h r o m a t o g r a m of p o l y c h l o r i n a t e d b i p h e n y l s (Aroclor 1254) e x t r a c t e d from C u m a r - t r e a t e d silo staves. Quantification was based on integrated areas of peaks 3 t h r o u g h 9.

from spiked concrete was a d e q u a t e and r e p e a t a b l e (86.47 + 1.50%) utilizing 2% benzene in p e t r o l e u m ether as the solvent. C h r o m a t o g r a p h i c "clean-up" m e t h o d s were not n e c e s s a r y as b a c k g r o u n d and blank samples revealed no interfering peaks for the staves within the elution time for Aroclor 1254 c o n g e n e r s with our GLC conditions. The p r o c e d u r e s employed did an e x c e l l e n t job of p r e v e n t i n g c r o s s - c o n t a m i n a t i o n d e s p i t e great differences in residue c o n c e n t r a t i o n among sections. The p r o c e d u r e was reliable as the c o e f f i c i e n t of v a r i a t i o n for d u p l i c a t e (> limit of a n a l y t i c a l sensitivity) and rerun samples was 7.29%. During this study the limit of analytical s e n s i t i v i t y was 0.025 ~g/g. The 14 silo staves c o l l e c t e d for this e x p e r i m e n t seem to represent m a n y p o s s i b l e stave c o n d i t i o n s that can be e n c o u n t e r e d on farms (Table i). Least-squares analyses of v a r i a n c e revealed s i g n i f i c a n t stave and section differences (P<.01) where p o s i t i o n effect was not s i g n i f i cant (P>.05). Table 2 s u m m a r i z e s the PCB c o n c e n t r a t i o n in s c r a p i n g s and sections of each stave. The data presented were averages of all p o s i t i o n s sampled. When c o n s i d e r i n g these results it is important that all of 55

0%

No.

Stave

OM-I OM-2 OCB-I ON-1 MM-I MM-2 MM-3 MM-4 MM-5 MM-6 MM-7 MM-8 MM-9 MI-I

2.

Table

2.14 85.51 259206.35 997.58 235.35 445.19 3.13 2.14 10.95 1.25 586.13 25.56 18.39 1.19

Scrapings

Penetration

PCB

1

into

.29 10.98 1639.51 221.23 53.37 49.01 .76 .07 3.80 .82 92.96 9.48 9.50 .04

Section

of

.00 .03 .29 20.09 .03 1.40 .00 .00 .00 .00 .33 .04 .54 .00

2

.00 .00 .14 .52 .00 .04 .00 .00 .00 .00 .05 .02 .47 .00

Section

Concentration

staves.

Section

PCB

silo

3

~g/g

.02 .00 .ii .00 .00 .01 .00 .00 .00 .04 .04 .04 .95 .00

Section

in 4

5

Section

.03 --.00 --.08 .43 .00 .17 .09 --.15 --.03 --.07 --.18 --. . . . . . .30 --.07 --.38 --.03 ---

Section

6

the staves c o l l e c t e d in Ohio were known to be coated across the entire inside surface (plain-staves) . M i c h i g a n Brand silos from the Charlotte, M i c h i g a n , plant have been reported to be of w a x e d ' s t a v e c o n s t r u c tion, thus staves c o l l e c t e d in M i c h i g a n m o s t l i k e l y were coated only on the joint mortar. Records are not a v a i l a b l e to verify the coating p r o c e d u r e s of the particular staves c o l l e c t e d for this study, however, higher c o n c e n t r a t i o n s near the edges (Positions A & C) of some of these staves would suggest that the joints were Cumar treated. S c r a p i n g s from the surface of all of the staves revealed the p r e s e n c e of p o l y c h l o r i n a t e d b i p h e n y l s when c o m p a r e d to standard Aroclor 1254. The thickness of these scrapings varied with c o m p o s i t i o n and c o n d i t i o n of individual staves. The m a x i m u m and m i n i m u m p a r t i c l e thickness of scrapings for each stave were m e a s u r e d . The average m a x i m u m thickness was 0.834 + 0.580 m~n and the m i n i m u m averaged 0.100 + 0.012 mm. The range of PCB c o n c e n t r a t i o n in s c r a p i n g s from these staves was > 250,000 ~g/g to ~ 1 ~g/g (Table 2). The former is p a r t i c u l a r l y s i g n i f i c a n t as Cumar coating was intact on the stave surface with c o n c e n t r a t i o n s of PCB a p p r o a c h i n g the theoretical m a x i m u m of 325,600 ~g/g based on reported Cumar formulations. When sections were cut from the staves all but one were found to be d e n s e l y c o n s t r u c t e d of c o n c r e t e and stone aggregate. The National brand stave (ON-l) from Ohio was v i s i b l y porous with traces of coating p e n e t r a t i n g b e y o n d the surface. The stave used in this s t u d y was e x p e r i m e n t a l l y coated in 1971 (Willett, 1974), thus there is little likelihood of National silos that contain Cumar. The average residue pattern of M i c h i g a n brand silo stave MM-9 (Table 2) s u g g e s t e d that p e n e t r a t i o n of PCB m a y have occurred. However, residue c o n c e n t r a t i o n s were g r e a t e s t in sections along the stave joints; thus Cumar m a y have p e n e t r a t e d between, not through, the stave. Except for the a f o r e m e n t i o n e d National (ON-I) and Michigan (MM-9) brand staves, these studies r e v e a l e d little p e n e t r a t i o n of residual PCB into the silo wall. Table 3 summarizes the amount of PCB in each section, thus the m a j o r i t y of the PCB was found in the first section (inside) of each stave which included the surface and 9 to 14 mm of concrete. Residual PCB was either n o n d e t e c t a b l e or in very low c o n c e n t r a t i o n s in subsequent sections through the stave until the outer surface. Most outside sections had a low PCB c o n t e n t , p r o b a b l y resulting from silage juices c a r r y i n g PCBs 57

ta O0

No.

Stave

OM-I OM-2 OCB-I ON-1 MM-I MM-2 MM-3 MM-4 MM-5 MM-6 MM-7 MM-8 MM-9 MI-I

3.

Table

86.41 99.76 99.94 91.77 99.73 97.55 97.10 96.36 96.50 97.42 99.31 98.58 82.52 65.85

Section

1

Distribution

in

.00 .24 .02 7.95 .05 2.09 .00 .00 .00 .00 .28 .35 3.67 .00

2

Amount

PCB

Section

of

of

PCB

.00 .00 .01 .20 .00 .06 .00 .00 .00 .00 .05 .19 3.55 .00

3

(% o f

staves.

Section

silo

in

4.85 .00 .01 .00 .00 .02 .00 .00 .00 2.58 .03 .30 6.82 .00

Section

total 4

8.74 .00 .01 .00 .22 .28 2.90 3.64 3.50 . . .33 .57 3.44 34.15

Section

sections)

.

5

.

.

. ---------

----.03 .07 -----------

Section

6

d o w n the o u t s i d e of the silo or c r o s s - c o n t a m i n a t i o n of s t a v e s w h e n s t a c k e d , a f t e r the s i l o s w e r e d i s m a n t l e d . A m o u n t s of PCB d e t e c t a b l e in all s e c t i o n s o t h e r than t h o s e a d j a c e n t to the inner wall ( s e c t i o n I) w e r e c o n s i d e r e d to be i n s i g n i f i c a n t . T h e s e r e s u l t s h a v e s h o w n that PCBs from the silo c o a t i n g c a l l e d C u m a r did not p e n e t r a t e s i g n i f i c a n t l y into the c o n c r e t e staves. Thus, w i t h the m a j o r i t y of r e s i d u a l PCB on the inner s u r f a c e of the silo, the PCB c o n t e n t s c r a p i n g s from this s u r f a c e can be used to e s t i m a t e the PCB c o n t e n t of the e n t i r e silo a s s u m i n g that the d e n s i t y of s c r a p i n g s are e q u a l to the e n t i r e s t a v e (2.3 g / c m ~ ) . The f o l l o w i n g f o r m u l a s w e r e d e v e l oped to e s t i m a t e the PCB c o n t e n t of a silo i r r e s p e c t i v e of size. For p l a i n - s t a v e silos, w h e r e the e n t i r e s t a v e s w e r e c o a t e d , c o n c e n t r a t i o n is e s t i m a t e d by: C

= C e

where:

s

C Ce Ds Ds w

= = = =

" Ds Dw

c o n c e n t r a t i o n in e n t i r e silo c o n c e n t r a t i o n in s c r a p i n g s d e p t h of s c r a p i n g s t h i c k n e s s of silo wall

In the case of M i c h i g a n B r a n d silos, w h e r e o n l y the j o i n t m o r t a r was c o a t e d w i t h C u m a r , less PCB is present. If the s c r a p i n g s w e r e c o l l e c t e d from the j o i n t m o r t a r of one of t h e s e silos, the c o n c e n t r a t i o n e s t i m a t e for the e n t i r e silo can be a d j u s t e d for the p o r t i o n not c o a t e d by the e q u a t i o n : C

=

.23

C

e

s

Ds Dw

This s t u d y has s h o w n that m o s t of the r e s i d u a l PCBs f r o m C u m a r - t r e a t e d silos can be f o u n d on or w i t h i n a few mm of the inner silo s u r f a c e . T h e r e f o r e , the PCB c o n t e n t of s c r a p i n g s from that s u r f a c e can be used to e s t i m a t e the PCB c o n t e n t of the e n t i r e silo. B a s e d on t h e s e e s t i m a t e s , the m a j o r i t y of P C B - c o n t a m i n a t e d silos w o u l d not e x c e e d 50 ~g/g in the total s t r u c t u r e and thus w o u l d not r e q u i r e d i s p o s a l in a h a z a r d o u s w a s t e facility. This is f o r t u n a t e b e c a u s e such d i s p o s a l w o u l d be t r e m e n d o u s l y e x p e n s i v e and w o u l d o c c u p y a g r e a t deal of v a l u a b l e s p a c e that c o u l d be u t i l i z e d for more hazardous materials. P r e s e n t l y , t h e r e are no u n i f o r m r e g u l a t i o n s d e f i n i n g the u l t i m a t e fate of silos w h i c h h a v e b e e n c o a t e d w i t h Cumar. In some a r e a s t h e y m a y be a l l o w e d to r e m a i n in use as long as no r e s i d u e p r o b l e m s r e s u l t , w h i l e in o t h e r s they m a y need to be c o m p l e t e l y a b a n d o n e d .

59

C u m a r - t r e a t e d silos are now at least 13 years old since the last reported uses of this coating were in 1970. Some date back to the early 1950s and late 1940s and have reached the end of their usefulness. Unless these older structures were recoated with Cumar, it is highly u n l i k e l y that they would exceed the federal 50 ~g/g regulation as most of the PCB has eroded or was dissolved from the silo wall. Since these staves contain only small amounts of PCBs, which are bound to the surface, they seem to r e p r e s e n t only a m i n i m a l future e n v i r o n m e n t a l hazard once removed from direct contact with humans, food, feed, or livestock. An extensive survey of 19,096 silos in M i c h i g a n has revealed 406 that c o n t a i n e d b e t w e e n .7 and 140,000 ~g/g PCB, with 50% < 1,000 and 90% < 8,500 ~g/g in scrapings. Since the m a j o r i t y of these silos surveyed are reported to have been only coated on the joint mortar, few would exceed the 50 ~g/g limit on a whole silo basis. Acknowledgements. This study was supported in part by Environmental Protection Agency Grant No. C S - 8 0 7 9 1 2 0 and gifts from Milk Marketing, Inc., and Michigan Milk Producers Assn. Journal Article No. 49-84, The Ohio State University, Ohio A g r i c u l t u r a l Research and D e v e l o p m e n t Center. REFERENCES W i l l e t t LB, Hess JF, Jr. (1975) P o l y c h l o r i n a t e d biphenyl residues in silos in the united States. Residue Reviews 73:135-147 Willett LB (1974) Coatings as b a r r i e r s to p r e v e n t p o l y c h l o r i n a t e d biphenyl c o n t a m i n a t i o n of silage. J Dairy Sci 57:816-825 W i l l e t t LB (1980) P o l y c h l o r i n a t e d b i p h e n y l s from d a i r y farms: C o n s e q u e n c e in m a r k e t milk. J Dairy Sci 63:1961-1965 Received

July

27,

1984;

accepted

60

August

27,

1984.