Skin absorption of aniline from aqueous solutions in man

Toxicology Letters, 10 (1982) 367-372 Elsevier

Biomedical

SKIN ABSORPTION

BOZENA

367

Press

OF ANILINE FROM AQUEOUS SOLUTIONS

IN MAN

BARANOWSKA-DUTKIEWICZ

Department of Analytical Chemistry, Institute of Chemistry and Physics, University Medical School of Silesia, 41-200 Sosnowiec, ul. Jagielioriska 4 (Poland) (Received

August

(Accepted

September

15th, 1981) 4th. 1981)

The skin absorption

of aniline,

SUMMARY

was investigated calculated aqueous mean

aniline with 3% water content,

in man. The time of exposure

on the basis of p-aminophenol solutions

was approx.

rate of absorption

excretion

in 24-h urine.

0.20 to 1.22 mg/cmVh.

of liquid

aniline

and 1 and 2% aqueous

was 30 or 60 min. The absorbed

The rate of aniline

There was no significant

(3.0 mg/cm*/h)

and that

aniline solutions

amount

of aniline was

absorption

difference

with 3% content

between of water

from the (2.5

mg/cm2/h).

INTRODUCTION

Numerous investigations [l-5] showed that under industrial conditions the skin is the main route of aniline absorption, which is connected with contamination of the skin and protective clothing with this substance. Trojanowska [4] found that aniline amounted to 2.0 mg/cm2 on the skin of workers and to 25.0 mg/cm2 on protective clothing. Aquantitative evaluation of aniline absorption was made by Dutkiewicz [l] for aniline vapours and by Piotrowski [3] for liquid aniline. The results were in good agreement as regards the excretion in urine of the aniline metabolite, p-aminophenol, after aniline vapour absorption through the respiratory tract and liquid aniline absorption through the skin. This was the basis for the elaboration of an exposure test for aniline in which the relationship between the absorbed amount of aniline and excretion rate of p-aminophenol were used [6]. However, no data were published regarding skin absorption of aqueous aniline solutions although they occur freq_uentl\! in this form under industrial conditions. 0378.4274/82/000&0000/$02.75

0 Elsevier

Biomedical

Press

368

Therefore, we set out to study and determine the rate of aniline skin absorption from diluted aqueous solutions. Attempts were also made to assess the influence of water on the rate of aniline absorption when it was added to the liquid aniline before topical application.

MATERIALS

AND METHODS

The study was performed on 10 healthy male and female volunteers aged 22-48 years who had no professional contact with aniline. They did not take any drugs before and during the experiment. The period of time between experiments with the same person was long enough to eliminate the effect of the preceding experiment. Previously elaborated methods for this type of experiments were applied [7, 81. In 14 experiments the hands (347-459 cm2) were immersed in 1 and 2% aqueous solutions of aniline. The time of exposure was 30 or 60 min and the temperature of the solution was 20 f 1 “C. The exposed area of the hand was geometrically measured and calculated for each person separately. Skin absorption of liquid aniline and aniline with 3% water was investigated in 12 experiments. Aniline in a volume of 0.25 ml was introduced under the watch-glass on a limited area of the forearm calculated to be 26.3 cm2. The time of exposure was always 30 min. At termination of exposure the skin was washed with water and soap. In all experiments the absorbed amount of aniline was calculated on the basis of the amount of p-aminophenol excreted in urine during 24 h from the beginning of the exposure. The ratio between the amount of aniline absorbed and the amount of p-aminophenol excreted was calculated by the method of Piotrowski [3]. l-h urine samples were collected during 8 h at the beginning of the experiment and subsequently at unrestricted time intervals. The determination of p-aminophenol in urine samples with known specific gravity was performed by the indophenol method of Dutkiewicz [6]. The accuracy of p-aminophenol determinations measured by the coefficient of variation was equal to 9.5% (n = 30). The normal level of p-aminophenol was calculated by the method of Dutkiewicz [l] and taken into account in all determinations.

RESULTS

The results obtained for absorption by the skin from aqueous aniline solutions are presented in Table I. The absorption rate increased with the increase of concentration and declined according to the time of exposure. The 2-fold increase of aniline concentration in water solutions caused about a 4-fold increase in the rate of skin absorption.

369 TABLE I ANILINE SKIN ABSORPTION FROM AQUEOUS SOLUTIONS Number Absorption area of experi- (cm2) ments

4 4 4 2

347-416 350-436 350-459 347-370

Time of absorption (min)

30 60 30 60

Concentration of aniline in water (%)

p-Aminophenol eliminated during 24 h

1 1 2 2

Absorption rate (mg/cm2/h)

Aniline absorbed (mg)

(mg) Range

Average

23.0- 37.5 29.1 25.0- 59.6 44.9 138.2-157.0 147.9 157.6-197.7 177.6

Range

Average

Range

Average

48.0- 71.0 53.0-100.0 222.0-242.0 242.0-352.1

58.3 80.4 232.1 297.0

0.28-0.35 0.15-0.24 1.05-1.38 0.70-0.95

0.32 0.20 1.22 0.82

The character ofp-aminophenol excretion in urine presented as a rate of excretion in function of time (Fig. l), was similar to that obtained by liquid aniline skin absorption or aniline vapour lung absorption [ 1, 31. The maximum excretion rate of p-aminophenol in the majority of experiments was between 4 and 6 h from the beginning of the exposure. Data concerning absorption of liquid aniline and aniline with 3% water are presented in Table II. Mean values of absorption rates were similar and amounted to approx. 3.0 and 2.5 mg/cm2/h, respectively. The statistical evaluation of the data presented in Table II based on the test of rank sums [9] showed that the observed difference in amounts of p-aminophenol excreted and aniline absorbed were accidental, statistically not significant (P = 95%).

1

2 3 4

5 6 7

8 9ioni213uismn~ez~,~b:::32

Fig. 1. Excretion rate of p-aminophenol

in urine in a subject exposed to 1% aniline solution for 1 h.

370 TABLE l1 LIQUD ANlLINE ABS~R~~~~~ Number of Form experiments

5

6

Liquid aniline Aniline + 3% water

THROUGH THE SKfN

~-Amjoo~be~oI elimi- Aniline absorbed nated during 24 h (mg) Cm@

Absorption rate (mg/cm*/h)

Range

Average

Range

Average

Range

Average

9.3-30.0

17.2

26.5-60.0

38.8

2.0-4.6

3.0

8.0-25.1

13.6

24.Q-5&O

32.7

f.8-3.8

2.5

The results indicate that skin absorption of aniline from its aqueous solutions occurred with great intensity. The rate of absorption of 1 or 29’0 aqueous aniline solutions is of the same order as for liquid aniline. The above comparison shows the essential influence of water as an accelerating factor of aniline absorption through the skin. Similar results were obtained by Piotrowski [3] for liquid aniline skin absorption and by Dutkiewicz fl] for aniline vapour skin absorption. Comparing the rate of skin absorption of liquid aniline and other industrial poisons (Table III) it could be shown that it is slightly lower than for carbon ~snl~hide [lo], benzene fl I], styrene, and xylene [I 2]. The absorption rate of 1 and 2% aqueous aniline sohuions is in the same range as of the abov~m~utioned substances in concentrations 100 times lower (Table III>. This comparatively high rate of skin absorption of compounds from their aqueous solutions seems to be a rule, which could be confirmed by numerous experiments [lo-121. It could be related to the hydration of stratum corneum. Scheuplein showed that water as a common vehicle plays an important role in increasing the permeabihty of stratum corneum [13]. On the other hand, the solubility of the pen&rant in the solvent also influences skin absorption” In case of poor solubifity in water of the applied substance it creates a convenient situation for penetration through the skin. The lipophilic action of the peuetrant changes the physical and chemical properties of stratum eorneum, whereas substances poorly soluble in water are easily liberated from the solution 114, 1st. If penetrants are easily dissolved in vehicles applied to the skin, penetration is more difficult. An example of such a situation could be given for carbon disulphide, which is absorbed through the skin in man about 100 times faster from aqueous solutions compared with oil solutions of the same concentration [16]. Similar differentiation was observed by Massman (after [l]) for aniline skin absorption in rats from aqueous and oil solutions.

371

TABLE III COMPARATIVE

DATA OF SKIN ABSORPTION OF SOME INDUSTRIAL POISONS Liquid

Aqueous solution

No. Substance

Time of exposure (min)

Absorption Time of rate exposure (mg/cm2/h) (min)

(1)

30 300 _

2.0 -4.6 0.18-0.72 _

10-15 10-15 10-15 S-15 5

5 14 22 9 9.7

(2) (3) (4) (5) (6)

Aniline Aniline Aniline Aniline Benzene Toluene Ethylobenzene Styrene Carbon disulphide

-12 -23 -33 -15

60 60 60 60 60 60 60

Concentration (g/l)

Absorption rate (mg/cm*/h)

Ref.

_

_

Our data

_ 10

_ 0.15-0.24

131 Our data

20

0.70-0.95

Our data

0.17-0.71

0.07-0.31

[ill

0.18-0.61

0.16-0.62

0.11-0.16

0.1 l-O.23

0.06-0.26 0.42-1.49

0.04-0.18 0.23-0.79

WI 1121 [121 HO1

The data in Table II show no substantial difference in skin absorption of liquid aniline and aniline with 3% water. The reason for this is that the water content of the applied substance is too small, limited by solubility, to cause the hydration of stratum corneum. Our data concerning liquid aniline skin absorption are similar to those of Piotrowski [3]. Slightly lower absorption rates obtained by this author could by explained by the longer (5 h) times of exposure. Table I also indicates that a prolonged exposure time results in lower absorption rates. The decreased absorption rate at longer times of skin contact with the applied substance is not unique and has been stated for various substances [8, 11, 12, 14, 171. It could be associated with the accumulation of aniline in stratum corneum and other skin layers which leads, by longer times of contact, to reduction of concentration differences and results in a reduced capability of diffusion. p-Aminophenol excretion in urine after application of aqueous aniline solutions is very similar to that after liquid aniline skin absorption [3] or aniline vapour absorption in respiratory tract [ 11. This proves the usefulness of the p-aminophenol test for the evaluation of skin absorption of aqueous aniline solutions. The results showed that aniline could present a risk as an industrial poison, also in case of skin contact with aqueous aniline solutions. Dutkiewicz [l] showed that the use of aqueous aniline solutions in industry - in dyeing animal furs and textiles led to skin absorption of >60% of the daily dose of aniline. Taking into account the rate of absorption of aniline from 2% aqueous solutions it could be calculated that the amount absorbed was 240 mg during a 30-min exposure (Table I). The absorption of aniline vapours in the respiratory tract during 8 h by 90% retention in concentrations equal to MAC of 5 mg/m3 acceptable in Poland is only 22.5 mg. This comparison is significant because the dermal toxicity of aniline is only two times lower than that of parathion and about eight times higher than that of benzene or carbon tetrachloride [18].

312

It should be emphasized that even single contact of skin with aqueous aniline solutions should be avoided. Exposure in industry should in any case be checked by means of the p-aminophenol test.

REFERENCES

1 T. Dutkiewicz, 2 D. Jamrog,

The Absorption

(in Polish),

Quantitative

Immunol.,

4 B. Trojanowska, 5 H.B. Elkins,

estimation

The pollution

(in Polish),

LTN, Lbdi,

investigations

1962.

in the dye industry

Chemistry

and B. Baranowska,

the skin in men, Excerpta 8 T. Dutkiewicz

through

the skin in man. J. Hyg. Epid.

Toxicology, (in Polish),

Absorption

Medica

and H. Tyras,

and amino-compounds

of the work clothes

and of the

Med. Pr., 6 (1959) 387.

of Industrial

Toxicological

7 T. Dutkiewicz

of aniline absorption

with nitro-

workers

The Chemistry

6 T. Dutkiewicz,

Congress

Wiley, New York, PZWL,

of carbon

Warszawa,

disulphide

1959, pp. 170-171. 1974, pp. 200-204.

from aqueous

solutions

through

Series No. 62, 2 (1963) 715.

A study of the skin absorption

of ethylobenzene

in man, Br. J. Indust.

24 (1967) 330.

9 J. Gren,

Mathematical

10 B. Baranowska, Absorption

PWN,

Warszawa,

on the absorption

CS2 and

its aqueous

and H. Tyras,

Bromat.

Chem.

12 T. Dutkiewicz and styrene

The absorption

Toksykol.,

and H. Tyras, through

13 R.J. Scheuplein, 14 V. Riihimaki,

solutions of benzene

Comparative

Mechanism J. Work

of percutaneous absorption

Environ.

the human

Nauk.

Bromat.

skin, II. Chem.

Acta Pol. Pharmac.,

18 R.L. Roudabush,

C.J.

and Occup.

Terhaar,

on the skin rabbits

the skin in man (in Polish),

Zes.

of toluene ethyl benzene,

xylene

J. Invest.

from a mixture

Dermatol.,

45 (1965) 334.

of m-xylene

and isobutyl

alcohol

5 (1979) 143.

factors

influencing

percutaneous

of carbon

absorption

disulphide

through

from dermatolothe skin from

oil

23 (1966) 406.

J. Koticzalik

in man, Int. Arch.

through

Med. Pr., 20 (1969) 228.

absorption,

of m-xylene

Health,

Some physical-chemical

17 B. Dutkiewicz,

chemicals

through Zes.

studies on the absorption

gicals, Curr. Probl. Dermatol., 7 (1978) 156. 16 T. Dutkiewicz and B. Baranowska, Absorption

methanol

disulphide

(in Polish).

1 (1968) 159.

the skin of man (in Polish),

Percutaneous

Stand.

15 D.E. Wurster,

solutions,

1974. of carbon

1 (1968) 121.

11 T. Dutkiewicz

in man,

Statistics,

Investigations

of liquid

Toksykol., Nauk.

in Man (in Polish),

Toxicological

23 (1957) 1.

skin, of dye industry

Med.,

of Aniline

and Z. Zaremba,

Med. Pr., 5 (1954) 278.

3 J. Piotrowski, Microb.

and Metabolism

I. Kesy, J. Piotrowski

W. Karwacki, Environ.

Skin absorption

Health,

D.W. Fasset and S.P. Dziuba,

and guinea

pigs. Toxicol.

and

per OS administration

of

47 (1980) 81. Appl.

Comparative Pharmacol.,

acute effects 7 (1965) 559.

of some