Document 4485G4NnYO9kwaEKLgRa5X17a

162 FRANK A. PATTY F. OTHER MEANS OF ABSORPTION 1. Ingestion Ingestion of toxic materials has been mentioned above as resulting from in halation. It may also result from many other sources, such as contaminated food, tobacco, or beverages, or from putting fingers or other contaminated objects into the mouth, or from licking the lips. Compared with inhalation, ingestion plays aminor role in the absorption of most toxic materials in industry. However, progres sive companies realize that occupational diseases can occur from the careless us6, of contaminated workrooms as a place in which to eat lunches--all too often with*' out previously washing the hands (cf. also page 130). S. Absorption through the Skin Many gaseous and liquid materials are absorbed to a limited extent through' the intact skin by way of the air spaces in the hair follicle to the sebaceous glands and the gland cells. Similarly, according to Rothman,18 any substance may, through the sweat gland ducts, reach the secretory surface of the sweat gland cells after having passed the straight and the convoluted part of the ducts. Most electrolytes and water do not penetrate the skin in significant amount^ Alkaloids, phenols, oxalic and salicylic acids and esters, lead acetate, and lead' oleate are absorbed in appreciable amounts. Salts of lead, tin, copper, arsenjc, bismuth, antimony, and mercury are said to penetrate by combining with the fat) acid-radicaLoL.the-seb.um..Ammoniated-mercury,..however,,,is-said_not-to_be_Al^- sorbed through the skin as such.18 Nicotine, strychnine, and opium are absorbed readily, but their salts are not. Slight amounts of hydrogen sulfide and rapidly dangerous amounts of hydrogen cyanide may be absorbed from contaminated ajn Nitrobenzene, dinitrobenzene, nitrotoluene, dinitrotoluene, (probably) trinitrotqf luene, aniline, dimethylaniline, and nitroglycerin are readily absorbed from s^irf contact with these materials or their solutions. Hodge and Sterner18 have shqwE that triorthocresyl phosphate is absorbed through the skin. Alcohols, aldehydes and acetone are said to be readily absorbed, but from a practical viewpoint there seems to be little significant hazard from this source. Benzene, toluene, xylene,th'e chlorinated hydrocarbons, and other fat solvents are absorbed to a degree, but the ..quantities.of..these.materials.accumulatedjn.tha.b).dy.in.this-manner_ar.e_pr,Qh"itiJ not ofea; significant ordei? although tetrachloroethane and, other.'unusuaH^'itrai'c solvents;fflayl;BC3exceptions to this statement. Absorption through lesions dicin' epiderinis.is much,more rapid than through the intact skin. ! itr. IV. Standards of Physiological Response In order to facilitate the comparison of data on the physiological response^ " S. Rothman, J. Lab. Clin. Med., 28, 1305 (1943). "H. C. Hodge and J. H. Sterner, J. Pharmacol., 79, 225 (1943). ENTRY AND ACTION OF TOXIC MATERIALS 163 ijnife'lation of atmospheric contaminants, many investigators have tabulated ; in degrees of response such as the following: .,u.d' tSfmount producing detectable or other degree of odor. ySniount producing detectable or other degree of irritation. iximum amount for repeated daily 8-hour exposures without injury. Sli\imum amount for a single 8-hour exposure without serious disturbance. Maximum amount for a single 1-hour exposure without serious disturbance. A'l'ioi.ntjdangerous to life within several (4 to 8) hours. 'Vomint dangerous to life within '/* to 1 hour. "Amount causing death within a few minutes. I i''vch set for industrial practice have been variously labeled as threshold -maximum safe concentration, maximum allowable concentration, toxic ,^maximum permissible concentration, and maximum safe practice. What is, o'urse, the most desired value is the maximum concentration to which an indilalm'aybe exposed throughout his or her working day, for an indefinite period me,'without suffering any ill effects. Unfortunately this has been established `'arVorily for extremely few single substances. The human body is fortified iefcnse, or detoxication, mechanism able to cope with all toxic materials in oaiua'bclow a certain level, called the threshold of intoxication. So long as this ""`old oi-daily intake is not exceeded, there are no harmful effects, but as soon ^Wfl- is exceeded, injurious effects result. This level is not a definite and oincifor any material, and it may vary not only with individuals, but also ^aijyiconditions of the same individual. There are many degrees or shades Jpftyijplmong the materials encbuntered'in ihdustry7 as, for 'inltafice, the volasoivent|WAll of these are toxic if absorbed into the system in excess, their ||feing a matter of degree, and none of them meriting the classification toxicljfHow are we to set permissible or safe standards of air contamination Vd^ip- !,,very few exceptions all of our so-called "safe" limits are educated |their best they are estimates rather than aotfialcsafe limits. They are |j|6sr careful consideration of available toxicity--data, largely obtained '' ,i of animals, which further research or experience may or may not pBfiftiyfo-y. then, pretend that we know the maximum safe limit unless, as " 'fprtfjj^g^qgi'monoxide and. other asphyxiants, lead, mercury, andr-possibly a m^|enalsjwe"liave*tEed'atatb establish the'poin7)Even_witlrthevaiphyx.x-uipk ,are not positive of the effects of prolonged inhalation of concenMSw to cause unconsciousness, and regarding the safe (limit for lead, points to a need for specifying the physical state and'chemical comIl'eadrTt-seemslogicaTthatwe'should/as-a-guidedxj'tlie-Uifinitiated, |0n the alarmist, and possibly the unscrupulous, without undue dep|sted'maximum concentrations for materials as soon as,iif' not1 before, jpfegustrial importance. We should call them hygienic standards, recomr L4?diP9cfd;>practice, tentative threshold limits, or suggested maximum concen- v i *, pi!