edited by MIRIAMC. NAGEL Avo" High School Avon. CT 06001
Chemical Pollutants in Perspective Miriam C. Nagel Avon High School A w n . CT 06001
In an address a t a Cancer Symposium in 1979, Charles Heidelberger of the University of Southern California Cancer Center said, "I think the public is tired of the carcinogen of the week." ( I ) . Far removed from such a prestigiousgroup of scientists, in a college chemistry laboratory session, a student told the instructor he did not want to continue in chemistry. The student said he did not want to be part of a profession that "pollutes the environment with chemicals." Widespread publicity about possible cancer-causing chemical oollutants. from DDT to dioxin, PCB's to EDB, &arms a& confuses the public. I t is little wonder that potential chemists are leanine toward "safer" career choices. Unfortunately, sensationalnews about a pollutant seldom includes a review of its histom. how useful i t was, or if it was developed specifically to meet some pressing need. Extensive toxicitv testine and environmental impact studies are relatively recent aiditions to the chemical world. They, t w , were born out of need-to mard against undesirable and unplanned consequences like thos;that followed the overuse of some pesticides. safety-minded chemistry teachers are concerned about the misuse of chemicals in and out of the laboratory. There are no easy "tips" on how to find the right answers for a negative student, but teachers should he able to discuss the issues with some knowledge and perspective.' Given some background in chemistry and the history of pollutants, students will be better prepared to make informed choices. Some students might even elect to accept the challenge and join in the search for-solutions. Chemical pollutants are chemicals that are in food, soil, water, or the atmosphere in amounts thought to be harmful. The chemicals may be safe, even desirable, if properly used. Chemicals that become pollutants have accumulated in unnatural amounts and locations where chance contact can cause distress to unlucky individuals. Circumstances surrounding that unsafe environment can be extremely varied. The book "Silent Spring" (2) in 1962 did more t o trigger public furor over chemicai pollution than any other single prior event. Pesticides, particularly, became the focus of concern. This discussion will trace the history of a few chemicals used t o control pests in order to give the chemistry teacher some ~
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' Carol Collins. Tampa, FL, and Michael E. Lewandowski,Somerset,
MA (chemistry teachers and reviewers for Safety Tips), suggest the
CMA film "Doing Something" as relevant to this column. Lewandowski also recommends Dow Chemical's film "Bill Smith's New Chemical." The films are available from Modern Talking Picture Service, 5000 Park Street North. St. Petersburg. FL 33709. ~
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Journal of Chemical Education
material for opening a discussion on the impact of chemicals on the environment. Although the dangers associated with toxic rhemicals were Franklin wrote of lead uoi~uninain not unnoticed IHeniamin . . 1786 (3)),i t is only in recent years that the h&ce of Ask versus benefit has been subiect to debate-with little aereement. The question of whois a t risk and who benefits too often manioulated. economicallv or ~oliticallv. Several &emiral; in use in srhbol lahoratori& were popular pesticides for renturies. Admittedly, must of the fear of pesticides today is hased on suspirion of rhe newer syntheticoraanic rhemicals, ones that are not "natural." This anxiety is not altogether unfounded, hut it is exaggerated out of ighoranee. Some highly toxic inorganic substances have been used as pesticides since ancient times. Had they been broadcast as widely as some modern pesticides have been, results would have been far more drastic than the havoc attrihuted to
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An 11th century Arab doctor recommended a cure for "lousy disease" t o be quicksilver, arsenic, and a change of clothes ( 4 ) !That may well be the earliest use of arsenic as an insecticide. Some arsenic compounds are still used for pest control. The safety of arsenic in wood preservatives for outdoor furniture has recently been questioned (5). Mercury compound^ are still used as seed treatments and for wood preservatives. The hazards of mercury are well documented. Students should he cold of its ilsc ar a pesticide. 'l'raaic incidents of the use of mercury-treated sieds as food are documented in "Mercury Contamination: A Human Tragedy" (6). I t is interestine that DDT came into popular use to combat s saved "lousy" diseases the 20th century. ~ G s o l d i e r were from disease in World War I1 bv dustines with DDT. A massive typhus epidemic in ~ a ~ l eright s , &ter the city was liherated, was brought t o an end in a few days by dusting everyone and the whole area with DDT. Planes routinely dispersed DDT over battle areas to prevent insecbborne diseases (7). I t is reported that more soldiers died of "lousy" diseases than of battle wounds in every war before WW 11.DDT and other new insecticides saved-many Allied soldiers, but the Germans did not use DDT and their losses to insect-borne diseases were heavy. According to the British Royal Army Medical Corps, "for every infested British soldier there were eieht thousand lousv Germans" (8). %he life-saving benefits resulting from the large scale use of insecticides in World War~I1 e x ~ l a~i n their s ~~r o f u s euse~in ~ the post-war period. Malaria is the most common insect-borne disease. Massive efforts were made to eradicate i t with chemical pesticides. Although malaria was not eliminated, the annual incidence of 250 million cases has been cut to 100 One reason for the limits to sucres with chemiral million (9). insecticides is the natural development of pesticide-resismt insects. This problem was recog&ed eve; before the DDT era. ~
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In the late 1800's fumigation of whole citrus trees with hvdrogen cyanide, HCN, w& an accepted method of pest contrh. It is mind boggling . . .to anvone concerned with chemical safetv to visualize trees enclosed in cloth tents which were filled with a predetermined amount of gas generated from potassium or sodium cyanide and sulfuiic &id. Whole orchards were treated by teams of fumigators. I t was an effective control for scale for quite a few years, but then the insects developed resistance to HCN and new control methods had to be found (10). The widespread use of pesticides favored the evolution of resistant insects. HCN had been used on a limited basis for centuries. Virgil reported seeing seeds being treated with crushed Cyprus leaves-now known to give off hydrogen cyanide. The seeds were then sowed just before a new moon (ll)! Copper sulfate is probablv one of the most commonlv used chemi&s in generalchemist& programs. I t is also wide& used as a pesticide. Pentahvdrate comer sulfate is used as an aericuliural fungicide, agicide, bactericide, and herbicide. some years ago, two im~ulsivecollege students were in charee of an outdoo.r municipal swimminppool u,hvn hor, humid weather hroughr on n sudden buildup of a l r : ~ They . had a barrel of CuSO4 crystals to use for such emergencies,-and, rather than read the directions, they simplv dumped the whole barrel of crystals into the pool when they closed it for the night. The next morning the day crew arrived to find an astonishing s i g h t a clear bright hlue pool! Fortunately, one of the students was a chemistry major and recognized the hazard of opening the pool to the public. Slowly-the water had to he changed over several days so the overflow stream would safely carry away the tainted water. EPA was not in existence at the time and no guidelines for solving a hlue pool problem were available. Copper sulfate has been used as a fungicide since the 1880's. Although mention is made in "The Pest War" that it was noted in 1846 that potatoes grown near a copper smelter in Wales did not suffer the common blight, the effectiveness of copper as a fungicide was not really appreciated until 1882. In that sear Millardet, a professor a t the Universitv of Bordeaux, ohserved healthy grape vines along the roadside when all the other plants had been shriveled by mildew. Local growers had sprayed the grapes along the road with a copper sulfate and lime mixture to make the grapes lwk unappetizing to passersby. Millardet tested various lime and copper sulfate mixtures for two years to see if i t was the solution to the mil-
dew. He oublished the eood news of his tests and Bordeaux mixture Lecame a common pesticide (12). Perhaps the erape mowers of France eot their insoiratiou for Bordeaux mixture from a similar slurry used against the destructive Colorado potato beetle which had made its way to Europe in 1875 (13). That year Germany imposed an emharao against US. and Canadian ootatoes. the fmt auarantine ever used to try to control plant diseases: The most effective insecticide against the potato beetle was Paris green. ; ( C . U \ A ~ O ~ ) ~ . C U I C ~made H ~ O into ~ I ~ ;a slurry with lime. .Inother deadly wsticide, a calcium arseniw waite product of the aniline dyeindustry called London purple, was &o used. The poisonous properties of the arsenic sprays were publicized, but little concern was expressed until 1920 when authorities in several American cities and England began confiscating fruits and vegetables with too much spray residue. This move foreshadowed present concerns. The oroblems of chemical ~ollutionfrom oesticides have rvol\.rd ovw centuries. There has been an enormous growth in world vor~ulntionsince 1939 when Paul Muller demonstrated tGe botency of DDT against the Colorado potato beetle. Before DDT there were onlv about 30 ~esticidesin common use. The need to feed the burgeoning population was one of the maior reasons for the wholesale develo~mentof modern pesticides. Large tracts devoted to single crops provide the means to feed the growing population, while they also provide the conditions for pests to multiply in numbers never known before. After the pest comes the pesticide, then the resistant pest, and so the war goes on. Somewhere safety has to fit into the picture, too. There is an ever recurrent need for concerned students with fresh ideas to enter chemistry. Literature Cited (1) Efmn. Edith. "The Apoeslyptirs? Simon &Schuster, New York. 1984,p. 233.
(2) Carson. Rachel, '"Silent Spring," paperback edition. Fawcett Publieations he., Greenmch. CT, 1962. (3) "The Franklin Letter on Lead Paisoning,"J. CHEM. EDUC., 58,274 (19811. (4) Odish, Gwrge. "The Constant Pest," Charles Snibnera Sons, New Yark, 1976, p.
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(5) The New York Times, July 12,1984,p. A19. (6) D'Itri. P. A,. and Dltti, F. M., "Mercury Cantaminstion: A Human Tragedy? John Wilov& Sona. New York. 1977. (7) K ~ I I ~ ~chem&, . E ~ ~43, ~8 (IWOJ. ~ ~ ~ ; (81 Oldish, reL ( 5 ) .p. 183. (91 Gunn,D. and stevcne,J.G.R., ( E d i ~ 0 ~ 1 , " ~ ~ t i c i d HHB~ d a n d weuar~,"odord University Press. Oxford. 1976,p. 30. (101 Ordish,ref.i5J.p.170. (11) 0rdish.ref. (5J.p.35. (12) Fletcher, W. W., "The Pest War,"John Wiley & Sons, New York, 1974, p. 82. (13) Carefod.G.L.,andSpmRE.R,"Famineonthe W i d ? h d M c N d y &Co.,Chicago, 1967.p. 143.
Volume 62
Number 5
May 1965
405
