Cotton Dust - ACS Publications - American Chemical Society

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Downloaded by UNIV OF CALIFORNIA SAN FRANCISCO on December 10, 2014 | http://pubs.acs.org Publication Date: July 1, 1982 | doi: 10.1021/bk-1982-0189.ch020

A n a l y s e s of the I n o r g a n i c C o n t e n t of C o t t o n D u s t : A Review R. E. FORNES, S. P. HERSH, and P. A. TUCKER North Carolina State University, School of Textiles, Department of Textile Materials and Management, Raleigh, NC 27650 R. D. GILBERT North Carolina State University, School of Textiles, Department of Textile Chemistry, Raleigh, NC 27650 Inorganics constitute a significant portion of cotton plant parts, soils and humidifier particulates which are known contaminants of dust generated by the processing of cotton. The inorganics are more easily extracted in a water medium than the organics. The lung disease byssinosis is widely considered to be induced by response to aqueous extractable components of cotton dusts which have penetrated the lower airways. Thus, complete characterization of cotton dusts is highly important in order to understand the relationship between cotton dusts and byssinosis. Samples of cotton dusts, trash, plant parts and other cotton dust contaminants and extracts of all of these have been studied by a number of investigators. A current review of these results is presented here. Cotton dust i s defined i n the Federal Register O ) as "dust present during the handling or processing of cotton which may contain a mixture of substances i n c l u d i n g ground-up plant matter, f i b e r , b a c t e r i a , f u n g i , s o i l , p e s t i c i d e s , non-cotton plant matter and other contaminants which may have accumulated during the growing, harvesting and subsequent processing or storage periods." Although the inorganic f r a c t i o n of cotton dust i s c o n s i dered by many (2^S) t o c o n t r i b u t e n e g l i g i b l y t o the problem o f b y s s i n o s i s , i t has been suggested by some t o have p o s s i b l e b i o l o g i c a l s i g n i f i c a n c e (9-16) and i t does c o n s t i t u t e a major p o r t i o n of the t o t a l dust found i n a cotton processing environment (11, The OSHA standard e s t a b l i s h e s a p e r m i s s i b l e exposure l i m i t of 200 ug/m for yarn manufacturing, 750 ug/m for s l a s h i n g and weaving, and 500 ug/m for a l l other processes i n the cotton industry and for n o n t e x t i l e i n d u s t r i e s where there i s exposure to cotton dust (J_) . The standard s p e c i f i e s that concentration i s 3

3

3

0097-6156/82/0189-0313$6.00/0 © 1982 American Chemical Society

In Cotton Dust; Montalvo, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1982.


314

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to be measured with a v e r t i c a l e l u t r i a t o r cotton dust sampler ( J _ ) , or i t s e q u i v a l e n t . T h i s instrument, which samples gravimetr i c a l l y the amount of dust below approximately 15-um aerodynamic diameter, was used i n the extensive epidemiologic s t u d i e s of Merchant, et a l . (22), i n which c o r r e l a t i o n s of dust concentrat i o n with prevalence of b y s s i n o s i s were made. Dusts c o l l e c t e d by t h i s instrument include not only p a r t i c u l a t e s a s s o c i a t e d with cotton but a l s o p a r t i c u l a t e s from background a i r or from other sources such as s o l i d s from h u m i d i f i e r water. T h i s l a t t e r source which i s mostly inorganic has been noted i n recent reports (23,24,25) to be the major component of cotton dust i n some cases. Inorganics a l s o c o n s t i t u t e a p o r t i o n of the plant c e l l components and show up as contaminants of p l a n t p a r t s and c o t t o n lint. I t i s t h e r e f o r e important that the inorganic composition of cotton dust be w e l l c h a r a c t e r i z e d . Studies of the i n o r g a n i c s i n cotton dust have incorporated the use of a wide v a r i e t y of techniques. These include X-ray fluorescence spectroscopy, atomic absorption spectroscopy, e l e c tron microscopy, energy d i s p e r s i v e a n a l y s i s of X-rays, X-ray d i f f r a c t i o n , atomic absorption spectroscopy, neutron a c t i v a t i o n a n a l y s i s and petrographic microscopy. I t i s necessary to use a wide array of techniques s i n c e no s i n g l e technique w i l l permit the measurement of a l l trace elements. Standard chemical t e c h niques to determine the ash content of samples and of v a r i o u s e x t r a c t s have a l s o been used. In most of these s t u d i e s the ash f r a c t i o n has been considered to be a reasonably accurate measure of the inorganic content. A major problem encountered by researchers who have attempted to c h a r a c t e r i z e cotton dusts using chemical, p h y s i c a l or b i o l o g i c a l t e s t s has been the choice of s u i t a b l e source m a t e r i a l . Many of the b i o l o g i c a l and chemical t e s t s r e q u i r e gram q u a n t i t i e s (sometimes kg q u a n t i t i e s ) of a sample i n order to c a r r y e x p e r i ments to completion. Since a v e r t i c a l e l u t r i a t o r sampler w i l l c o l l e c t only a few mg of dust per operating day i n t y p i c a l cotton processing environments (15,26), i t i s not p r a c t i c a l to c o l l e c t l a r g e q u a n t i t i e s of dust samples with t h i s instrument. Much of the work to date has been done on samples which have been r e l a t i v e l y easy to o b t a i n i n large q u a n t i t y . These include i n v e s t i gations of cotton plant p a r t s , e s p e c i a l l y the bract and leaves s i n c e these are known to be major vegetable contaminants i n c o t ton l i n t (27,28,29)• Some workers have r e s o r t e d to use of coarse t r a s h m a t e r i a l s c o l l e c t e d at various stages i n processing (8,15, 30,31)• Others have used dusts from e l e c t r o s t a t i c p r e c i p i t a t o r s (11,15,26,31,32), dusts c o l l e c t e d on f i l t e r s (8,20,31,32,33) and dust c o l l e c t e d by bubbling card room a i r through water (34). Brown and B e r n i (26) developed a novel method to separate f i n e dusts ( i n the r e s p i r a b l e range) from c o t t o n trash m a t e r i a l . The dust i s separated on s i e v e s by mechanical a g i t a t i o n . The t r a s h t y p i c a l l y c o n s i s t s of condenser f i l t e r cake m a t e r i a l c o l l e c t e d by an a i r f i l t r a t i o n system attached to a processing unit such as a


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cotton c a r d . Samples c o l l e c t e d by t h i s method have been i n v e s t i gated e x t e n s i v e l y i n recent years (17 18,19,26,30,31,35). f


A n a l y s i s o f Cotton Plant Dusts Several i n v e s t i g a t i o n s have been made of the ash contents o f cotton bracts and other plant p a r t s . Wakelyn, et a l . , (36) r e ported ash contents of seven samples of b r a c t s ranging from 10.6% to 22.0%. One of these was a g l a n d l e s s v a r i e t y which had a r e l a t i v e l y low ash content (13.7%). Another of the samples was a low glanded v a r i e t y and i t also showed a low ash content (10.6%.). With the exception of a sample qrown i n Arkansas, a l l samples were grown i n Texas. These samples were analyzed for inorganic elemental composition using X-ray fluorescence spectroscopy. For the glanded v a r i e t i e s (4 samples) the elements analyzed and t h e i r concentration i n the sample are shown i n Table I. TABLE I Elemental Analyses of Cotton Bracts (X-ray fluorescence) Element

Percentage

Ti Fe Zn Cu Si S CI K Ca Mg P Total % a

b

of Sample

0.001 0.014 0.002 0.008 0.55 1.26 1.63 1.88 4.22 1.34 1.17 12.25

b

(36)

(Range) (trace (0.007 (0.001 (0.005 (0.42 (0.85 (0.006 (1.28 (3.89 (1.16 (1.04 (10.37

-

0.001) 0.025) 0.004) 0.015) 0.77) 1.64) 2.91) 2.17) 4.48) 1.55) 1.31) 13.74)

average of 4 samples average of 3 samples

Part of the s i l i c o n i s most l i k e l y a s o i l contaminant on the surface of the b r a c t s while most of the other major elements detected are known to be p l a n t n u t r i e n t s . S i l i c o n and s i l i c a t e s have been detected i n a number of other p l a n t m a t e r i a l s (37,38). The plant n u t r i e n t s n i t r o g e n , phosphorous and potassium have been reported as a f u n c t i o n of the maturity of cotton p l a n t s (39). Bract samples from 14 l o c a t i o n s were i n v e s t i g a t e d by others over a three year p e r i o d (15,21). The average ash content of these samples was 18.0% (see Table I I ) . Results were reported a l s o for cotton l e a f , stem and bur. The ash content of l e a f


COTTON

316

DUST

m a t e r i a l was s l i g h t l y lower than bract while the ash contents of stem and bur were s u b s t a n t i a l l y lower. The bract and l e a f mater i a l s have a much higher surface to volume r a t i o and i t f o l l o w s that surface s o i l contamination would l i k e l y be higher for b r a c t s and leaves than for stem or bur. Ash contents were reported for d r i e d aqueous e x t r a c t s of these m a t e r i a l s . The plant p a r t s were f i r s t ground to 40 mesh i n a Wiley M i l l , mixed i n a r a t i o of 1 g sample/10 ml d i s t i l l e d H 0, e x t r a c t e d at room temperature for 1 hour, f i l t e r e d through a coarse f i l t e r followed by f i l t r a t i o n using a 0.45 m pore f i l t e r and then d r i e d i n a vacuum d e s i c c a tor. For a l l samples i n v e s t i g a t e d , the ash contents of the d r i e d e x t r a c t s were s i g n i f i c a n t l y higher than that i n the raw sample. As shown i n Table I I , the ash contents increased by approximately 2-fold for bract and l e a f and about 5-fold for stem and bur. The authors argued that i f the mechanism by which cotton dust i n t e r acts with the pulmonary f u n c t i o n i s through an aqueous e x t r a c t i o n of m a t e r i a l deposited i n the airways, the inorganic f r a c t i o n should not be ignored since i t i s the most r e a d i l y e x t r a c t a b l e .


2

TABLE I I

of

Sample Type

Bract Leaf Stem Bur c

D

Ash Contents of Cotton Bract, Leaf, Stem, Bur, and Gin Trash Samples; and Ash Contents the Dried Aqueous E x t r a c t s of these Samples (21) 3

No.

38 26 28 27

Average ash content (range), %

18.0 16.6 7.2 7.5

(8.6-27.7) (9.3-26.6) (2.2-12.5) (4.1-12.0)

No.

38 26 28 26

Average ash content of d r i e d aqueous e x t r a c t s (range), %

36.5 35.2 33.6 37.1

(26.1-43.7) (14.6-63.0) (19.1-50.4) (22.4-49.0)

a

Samples were c o l l e c t e d over 1974 and 1975 crop years. Values are the average of a l l samples of a given type. ^Includes samples c o l l e c t e d from the 1973 crop season. A sample with ash value of 57% was omitted from average. C

It was noted i n the work of M i t t a l , et a l . (21) that b r a c t samples taken from cottons grown under a r i d c o n d i t i o n s tend to have higher ash contents than those grown i n regions with r e l a t i v e l y high r a i n f a l l . I t was a l s o noted that the v a r i a t i o n i n ash contents of bracts as a f u n c t i o n of year of harvest was about the same as the v a r i a t i o n of ash contents between the fourteen l o c a t i o n s i n t h e i r study. B e r n i and coworkers (40) used energy d i s p e r s i v e X-ray


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Analyses of Inorganic

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techniques and X-ray fluorescence spectroscopy to i n v e s t i g a t e the elemental p r o f i l e s of cotton b r a c t , l e a f , stem and bur (pericarp) m a t e r i a l s . The o b j e c t i v e of t h i s work was to e s t a b l i s h a means to i d e n t i f y the amount of cotton plant p a r t s contained i n bulk cotton dust samples. Results of the X-ray fluorescence a n a l y s i s are shown i n Table I I I .


TABLE I I I Elemental Percentages of Cotton Plant P a r t s Leaf

Bract b

Stem

3

(40) Pericarp

Element

Mean

S.D.

Mean

S.D.

Mean

S.D.

Mean

S.D.

Ca Mg K CI S Si Al

3.91 1.42 1.07 1.26 1.12 0.75 0.11

1.47 0.44 0.77 1.33 0.50 1.05 0.18

3.34 1.05 2.06 1.08 0.98 1.24 0.16

1.08 0.75 1.17 0.77 0.38 1.32 0.17

0.81 0.26 1.35 0.64 0.20 0.06 0.13

0.40 0.11 0.91 0.60 0.11 0.08 0.11

0.29 0.31 2.86 0.68 0.30 0.45 0.32

0.13 0.55 0.94 0.49 0.07 0.57 0.39

Determined on bulk cotton dust samples from plant parts X-ray fluorescence, averaged over eleven samples. *S.D. - Standard Deviation using a l l eleven p a r t s .

by

Using a s t a t i s t i c a l d i s c r i m i n a n t a n a l y s i s , Berni and coworkers (40) were able to use the r a t i o of elements to d i s t i n g u i s h l e a f and bract from stem and p e r i c a r p . However, they were unable to d i s t i n g u i s h l e a f from bract or stem from p e r i c a r p . They a l s o noted that cotton seed h u l l p a r t i c l e s had c h a r a c t e r i s t i c s s i m i l a r to stem and p e r i c a r p . Calcium was the major inorganic element detected i n l e a f and bract while potassium was highest i n stem and p e r i c a r p . Their r e s u l t s were averages of plant parts from eleven f i e l d s and f i v e geographic l o c a t i o n s . The v a r i a t i o n s were high with c o e f f i c i e n t s of v a r i a t i o n surpassing 100% i n some cases. The f r a c t i o n of the t o t a l mass accounted for by the e l e ments analyzed was 9.5% and 9.9% for l e a f and b r a c t , r e s p e c t i v e ly. Fornes and coworkers (15) used X-ray d i f f r a c t i o n to i d e n t i f y potassium c h l o r i d e and potassium s u l f a t e , both of which had been p r e c i p i t a t e d from concentrated s o l u t i o n s of aqueous e x t r a c t s of b r a c t s . Potassium c h l o r i d e was estimated to be about 1-2% of the s o l i d s i n the aqueous e x t r a c t s . Hersh and coworkers (16,41) used energy d i s p e r s i v e X-ray spectroscopy to i d e n t i f y potassium c h l o r i d e p r e c i p i t a t e s from water e x t r a c t s of b r a c t s . They a l s o i d e n t i f i e d sodium, magnesium, aluminum, s i l i c o n , i r o n and copper i n d r i e d aqueous ext r a c t s of b r a c t s . No q u a n t i t a t i v e analyses were made.


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Analyses o f Card Room and Other T e x t i l e M i l l Dusts A number of i n v e s t i g a t o r s have reported proximate analyses and elemental composition of t e x t i l e m i l l dusts and t r a s h . Only two of these involve s t u d i e s of dusts c o l l e c t e d with an e l u t r i ator sampler (20,31). Samples from both of these s t u d i e s were c o l l e c t e d i n a model card room at North C a r o l i n a State U n i v e r s i t y (42). In one of these, g l a s s f i b e r f i l t e r s were used and the dusts were analyzed for average ash contents (see Table I V ) . The t o t a l ash content was about 20%. The average ash content of area samples also c o l l e c t e d on g l a s s f i l t e r s was found to be s l i g h t l y lower• TABLE IV Ash contents of dusts c o l l e c t e d on

Sample No. 1 2 3 4 5

a

Days collected 4 7 4 6 8

fiber -glass

E l u t r i a t o r samples Ash Dust collected content mg % 2.64 4.33 1.85 2.83 3.69

27.6 26.3 23.8 12.7 10.3

f i l t e r sa

(11)

Area samples Ash Dust content collected mg % 1.07 3.23 1.49 2.34 3.19

30.4 22.9 19.5 18.0 7.2

2.26 17.6 Avg. 3.07 20.1 One set of samples gave a negative ash value for both the e l u t r i a t o r and area samples and i s not included.

In the other study, X-ray fluorescence spectroscopy was used to analyze trace element concentrations by observing dusts on 37 mm diameter c e l l u l o s e acetate f i l t e r s (20). Twenty-three e l u t r i a t o r and twenty-three area samples from 10 d i f f e r e n t bales of cotton were analyzed. The average f r a c t i o n of t o t a l dust accounted for by the elements analyzed was 14.4% and 7.6% for v e r t i c a l e l u t r i a t o r and area samples, r e s p e c t i v e l y . Although the v a r i a t i o n i n absolute q u a n t i t y of an element was high, the r e l a t i v e abundance of an element was c o n s i s t e n t for measurements w i t h i n a b a l e . Averaged over a l l the samples analyzed, calcium was the most abundant element detected (3.6%), followed by s i l i con (2.9%), potassium (2.7%), iron (1.1%), aluminum (1.1%), s u l f u r (1.0%), c h l o r i n e (0.8%) and phosphorous (0.6%). Other elements detected i n smaller amounts included t i t a n i u m , manganese, n i c k e l , copper, z i n c , bromine, rubidium, strontium, barium, mercury and l e a d .



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Much of the v a r i a t i o n i n absolute q u a n t i t y of an element was shown to be due to v a r i a t i o n i n dust c o n c e n t r a t i o n . The c o r r e l a t i o n c o e f f i c i e n t s of l i n e a r r e g r e s s i o n models p r e d i c t i n g the concentration of calcium and s i l i c o n from the v e r t i c a l e l u t r i a t o r dust c o n c e n t r a t i o n were 0.89 and 0.79, r e s p e c t i v e l y . Recent reports suggest that a s i g n i f i c a n t p o r t i o n of the dust measured by a v e r t i c a l e l u t r i a t o r i n a card room may be due to s o l i d s i n h u m i d i f i e r water (23,25,43). Undoubtedly, much of the inorganic matter found i n the model card room dusts a r i s e s from t h i s source. Table V shows a t y p i c a l p r o f i l e of elements i n dust on a v e r t i c a l e l u t r i a t o r sample. Brown and Berni (26) analyzed the elemental composition of four card room dusts using X-ray fluorescence spectroscopy. Two of these were from f i l t e r cake m a t e r i a l c o l l e c t e d i n two t e x t i l e m i l l s from which f i n e dusts ( Cr Mn Fe Co Ni Cu Zn Ga Ge£ As Se Br Rb Sr Cd Sn Sb Ba b

b

b

b

b

b

b

b

Hg Pb

Concentration ± standard deviations ng/m ng/cm 3

2317 8579 2051 5411 11369 9897 17235 237 -43 -70 117 3067 4 42 949 249 -5 3 13 -8 21 17 125 -29 - 7 39 569 39 69 36

2

± 342 + 469 + 149 + 287 ± 578 + 498 ± 864 + 89 ± 46 ± 28 ± 25 ± 161 ± 17 ± 11 ± 53 ± 20 ± 6 ± 9 ± 9 ± 4 ± 8 ± 5 ± 16 ± 14 ± 20 ± 21 ± 112 ± 22 ± 16 ± 14

461 1708 408 1077 2263 1970 3431 45 -9 -14 23 611 1 8 189 50 -1 1 3 -2 4 3 25 -6 -1 8 113 8 14 7

+ + + + + + + + + + +

± + + + +

± ± ± ± ± ± ± ± ± ± ± ± ± ±

68 93 30 57 115 99 172 18 9 6 5 32 3 2 11 4 1 2 2 1 2 1 3 3 4 4 22 4 3 3

Element content expressed

Cotton Dust - ACS Publications - American Chemical Society

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