L~ttm to the Editor
that not only first but also recurrent events of disease during the study period are taken into account. Thus a rate difference, ER, - ERr, between the index (exposed) and reference populations indicates the excess number of episodes per persontime in the exposed population. A twosided confidence interval can be calculated based on the normal distribution assumption RD(1 ± ZJX), where Z is the critical ratio (1.96 with 95% confidence interval [Cl]) and X is test statistic. The chisquare test statistic is calculated using the observed (0) and expected number of episodes (E) in polluted and reference populations during the study period: X2 =
(O-E)/E
In our studywe used information collected during a MMR vaccination program, where the interviewer asked the mothers about the number of upper respiratory infection episodes experienced by the child during the previous 12 months (Table 1). Unfortunately, the information was coded in categories (0, 1-4, 5-9, 10-), which lead us to use the odds for experiencing one or more episodes during the past year. However, a crude estimate of ER in different study populations can be estimated by assiging for each category an average number of episodes: 0, 2.5, 7.0 and 10. The average for the last category is the most arbitrary. The episode rate of URI among the younger children of the polluted city was 3.1 episodes per person-year and 2.6 in the reference cities, giving a RD of 0.5 episodes per person-year (95% CI: 0.4-0.6) (Table 2). The corresponding figures for the older children were 2.0, 1.7, and 0.3 (0.1-0.5). Accordingly, ER for the younger children in the more polluted area (3.3) compared to those of less polluted area (2.8) gave a RD of 0.5 (0.1 - 0.9) and the corresponding figures for the older children were 2.2, 1.9, and 0.3 (-0.1 0.7). These crude RDs are not likely to be seriously confounded, while the corresponding crude odds ratios did not differ essentially from those adjusted for the confounders in the logistic regression analysis.3 The different analyses do not change qualitatively our findings, which suggest that children's respiratory health can be jeopardized from air pollution in concentrations lower than reported in most earlier studies from Europe. We would also like to point out that the estimated magnitude of the effect, 0.3 to 0.5 extra epiJune 1992, Vol. 82, No. 6
sodes a year, has a considerable public health importance. 0 Jouu J.L Jaakkok MD 0( P. Heinen, MD, DSc Requests for reprints should be sent to Jouni J.K. Jaakkola, MD, Helsinki University of Technology, Kl/Ko 302, Otakaari 4 A, SF02150 Espoo, Finland.
References 1. Miettinen OS. Theoretical epidemiology. P,incpls of occurence research in medicine. New York, NY: John Wiley & Sons; 1985:246-249. 2. Rothman KJ. Modem ep iogy. Boston, Mass: Little, Brown and Company; 1986:24. 3. Jaakkola JJK, Paunio M, Virtanen M, Heinonen OP. Low-level airpollution and upper respiratory infections in children.AmJPublic Health. 1991;81:1060-1063.
Plague Surveillance in Los Angeles County In 1986 Los Angeles County began a plague surveillance program because the number of human plague cases had increased. (uring the past 50 years, all human cases have occurred since 1978, including 3 in 1984.) Reagents and quality control were supplied by the CDC Plague Laboratory. Groups participating in the study included the countyveterinarian, animal shelters, county vector control, the agriculture commissioner, and the California State Polytechnic University, Pomona. Between 1986 and 1990,4,484 animal sera were tested for passive hemagglutination antibodies to Yerismia pestis, with 113 animals having antibody titers of 1:16 or higher. The titers ranged from 1:16 to 1:512, with the most common (modal) titer being 1:32. The largest number of seropositive animals were seen in 1987 (43) and the smallest in 1990 (2). Ground squirrels, dogs, coyotes, and black bears accounted for 109 (96%) of the seropositive animals. Additional seropositive animals included two cats, one fox, one raccoon, and one wild boar. Over half (60) of the seropositive animals were ground squirrels. Of the over 2000 shelter dogs tested, less than 1% were seropositive. Owned dogs were useful in areas of suspected plague epizootics. Two camp dogs were seropositive (1:32, 1:64) in 1987 at Camp Barley Flats, a correctional facility. Yersinia pestis was isolated from a dead ground squirrel found on the premises.
The animals most often seropositive were black bears (75%), wild boar (9%o), coyotes (6%), and ground squirrels (5%).
The seropositive rate for ground squirrels and coyotes was comparable to what was detected 10 years earlier.' Autopsies were performed on most of the coyotes. There were no histopathologic lesions suggestive of plague in any coyote examined. Most coyotes examined were under 1 year of age. Urban coyotes are useftl in plague surveillance of large areas. Wild carnivore provide a practical plague monitoring system. Although black bears and wild boars make good sentinels, they are uncommon in the semi-urban areas of Los Angeles County where most human exposure occurs. Ground squirrels are useful in pinpointing a location where a plague epizootic is occurring or has recently occurred. When ground squirrels are not available, domestic and wild carnivores are useful monitors.2-4 [] C. Pabick RPwn, DVM, MPH P. Eric Hughes, DVM GeorW Ma lsmoto, BA, MT Requests for reprints should be sent to C. Patrick Ryan, County of Los Angeles, Department of Health Services, Comparative Medical and Veterinary Services, 12824 Erickson Avenue, Downey, CA 90242.
References 1. Nelson BC, Madon MB, Tilzer A. The complexities at the interface among domestic/ wild rodents, fleas, pets, and man in urban plague ecology in Los Angeles County, California. In: Proceedings of the Twelfth Vertebrate Pest Conference; 1986:88-96; University of California, Davis. 2. Rust JH, Miller BM, Bahmanyar M, Marshall JD, et al. The role of domestic animals in the epidemiologyof plague. II. Antibodyto
Yeristiair in sera of dogs and cats.Journal of Infectious Diseases 1971;124(5): 527-31. 3. Rust JH, Cavanaugh DC, O'Shita R, Marshall JD. The role of domestic animals in the epidemiology of plague. I. &perunental infection of dogs and cats. Joumal ofInfectious Diseases 1971;124(5):522-26. 4. Nelson JH, Decker MD, Barnes AM, et al. Plague surveillance usingwild boar and wild carivore sentinels.JownalofEnviron,nen-
tal Health 1985;47(6):306-309.
Epidemiologic Studies on Electromagnetic Fields and Cancer Articles in the popular press alleging hazards of electromagnetic fields (EMFs) have contained misconceptions. In particular, in articles by Paul Brodeur in The New Yot*r magazine (and a book dealing with essentially the same information) that state a strong association between exposure to EMFs and cancer, the scientific
American Journal of Public Health 897
Letters to the Editor
evidence was oversimplified, the data were misinterpreted, and the body of work in this area in the scientific literature was ignored (for example, see Foster's review'). Also, the validity of citations of Brodeur's articles in the medical and scientific literature has been questioned.2 Several additional misconceptions have been presented in two more recent articles by Brodeur in The New Yorker. Most of the evidence Brodeur cited for the alleged association comes from epidemiologic studies. In "Annals of Radiation: Calamity on Meadow Street,"3 Brodeur cited a 1979 study containing numerous flaws that he chose to ignore. Michaelson4 and Poole and Trichopoulos5 have presented detailed analyses of some of these flaws. Brodeur also wrote that data from one study6 showed "four times the expected rate of brain cancer in children whose mothers used electric blankets." Brodeur had selected the subgroup with the highest odds ratio in the study, one that represented only 9% of the total population studied for prenatal electric blanket exposure. The odds ratio for association of all prenatal electric blanket exposures with the incidence of childhood cancer was only 1.3. In one study,7 according to Brodeur, "children whose fathers were electricians ran three and a half times the risk of developing tumors of the central nervous system than other children ran." Brodeur insinuated that this finding related to EMF exposure. In that article, however, the ratio was related not to fathers with jobs involving potential EMF exposure, but rather to "fathers who were electricians." This is an important distinction. The odds ratio for jobs in industries involving potential EMF exposure was only 1.6. The authors stated, "the highest risk estimate in our analysis was the odds ratio of 10.0 for construction electricians . . . (who) work largely with unenergized wiring, implying that they have a limited exposure to electromagnetic fields." Brodeur's reference to a cancer cluster in association with EMF exposure lacked a cause-and-effect relationship. An epidemiologist from a state health department has stated that "our investigation of a cluster of brain cancer cases ... was severely hampered by local reaction to the inaccuracies and misconceptions in The New Yorker article."8 Others have expressed similar complaints.8 In "Deartment of Arnpklfcation,"9 Brodeur stated that "eye melanoma .. has been found to be 'notably high for electrical and electronics workers,' who 898 American Journal of Public Health
are known to be exposed to strong magnetic fields." Yet the cited study10 did not mention exposure to EME. Brodeur also stated that "melanoma of the skin is ... prevalent amongworkers in electrical and electronic occupations, and thus associated with exposure to magnetic fields." Occupational titles, however, are a poor means of assessing potential EMF exposure. Brodeur called for several departments of health to conduct full-scale investigations of alleged EMF hazards. Yet it is questionablewhether the money spent on such investigations would be justified. As Weisburger11 has explained, "with limited funds available for serious research efforts, a program on electromagnetic fields and cancer could be counterproductive by diverting effort and money from more relevant research and public information activities." In contrast to Brodeur's claims, the majority of epidemiologic studies do not support the contention that there is an association between EMF exposure and cancer.12 His highly speculative and unsubstantiated claims should not be accepted as representing the scientific literature dealing with EMFs. Public health experts should be aware of these misconceptions and must challenge the appearance of such accounts in both the popular press and in medical and scientific journals. [1 James R. Jauche, PhD Requests for reprints should be sent to James R. Jauchem, Directed Energy Division, Occupational and Environmental Health Directorate, Armstrong Laboratory, Brooks Air Force Base, TX 78235. The opinions are those of the author and do not necessarily state or reflect those of the US government.)
References 1. Foster KR. Book review-Currents of death: Power lines, computer terminals, and the attempt to cover up their threat to your health. IEEE Eng Med Biol Mag.
1990;9(1):89.
2. Jauchem JR. Electromagnetic fields: Is there really a danger? Lancet 1990;336:884. Letter. 3. 7he New Yorker. July 9, 1990. 4. Michaelson SM. Household magnetic fields and childhood leukemia: a critical
analYsis. Pedatrics. 1991;88:630-635.
5. Poole C, Trichopoulos D. Extremely lowfrequency electric and magnetic fields and cancer. Cancer Causes ControL 1991;2: 267-276. 6. Savitz DA, John EM, Kleckner RC. Magnetic field exposure from electric appli-
ances and childhood cancer. Am JEpide-
miot 1990;131:763-773.
7. Johnson CC, Spitz MR. Childhood nervous system tumours: an assessment of
risk associated with paternal occupations involving use, repair or manufacture of electrical and electronic equipment. Int J EpidemnioL 1990;18:756-762. 8. Newman ME. Electromagnetic fields and cancer-Media and public attention affect research.JNatlCancerInst. 1991;83:164166. 9. 7he New Yorker. November 8, 1990. 10. Swerdlow AJ. Epidemiology of eye cancer in adults in England and Wales, 1962-1977. Am JEpideniology. 1983;118:294-300. 11. Weisburger JH. Cancer and electromagnetic fields. Lancet. 1990;336:1259. Letter. 12. JauchemJR, MerrittJH. The epidemiology of exposure to electromagnetic fields: an overview of the recent literature.JClin EpidemioL 1991;44:895-906.
The Correct Use of Growth Charts It is with great interest that I read the article by M. T. Ruel, D. L. Pelletier, J.-P. Habicht, et al., "Comparison between two growth charts in Lesotho" (Am J Public Health. 1991;81:610-615). I was surprised to see that both emphasize percentage deficit, which is taken as a percentage of the median of the reference population. My experience in different places (most recently in Indonesia) is that health workers feel that, on a Road-toHealth (RHT) chart that carries the top of the "green" at the male median W/Age, anyone who falls beyond the top line (i.e., in the white part) is "abnormal." I am very glad that at least the RHT was chosen as the more effective chart and that both mothers and health workers had a better understanding of the process indicated on the card. As it is, teaching is usually done the wrong way round: the chart should not be an initial indicator but a tool for the evaluation of growth; the advice given is the most important. The Guideline should come first, with the feeding advice, then the weighing to see if the mother's efforts have bome fruit-this is the original process of child health care. The interview with the mother-not the chart-gives the answers regarding good or indifferent care. Many children bom at or above the chart median can stay there without any problem, but health workers are quite happy if they "flatten off" into the "green" until they approach the 80%o line, and in some countries supplementary feeding may start only at the 60%o line. I wonder why the Catholic Relief Service Food and Nutrition Programme still uses the GS card with its unphysiologic implications? Especially in Africa, one would not expect the well fed to deviate too farfrm the National Center for Health Statistics distribution-
June 1992, Vol. 82, No. 6
that not only first but also recurrent events of disease during the study period are taken into account. Thus a rate difference, ER, - ERr, between the index (exposed) and reference populations indicates the excess number of episodes per persontime in the exposed population. A twosided confidence interval can be calculated based on the normal distribution assumption RD(1 ± ZJX), where Z is the critical ratio (1.96 with 95% confidence interval [Cl]) and X is test statistic. The chisquare test statistic is calculated using the observed (0) and expected number of episodes (E) in polluted and reference populations during the study period: X2 =
(O-E)/E
In our studywe used information collected during a MMR vaccination program, where the interviewer asked the mothers about the number of upper respiratory infection episodes experienced by the child during the previous 12 months (Table 1). Unfortunately, the information was coded in categories (0, 1-4, 5-9, 10-), which lead us to use the odds for experiencing one or more episodes during the past year. However, a crude estimate of ER in different study populations can be estimated by assiging for each category an average number of episodes: 0, 2.5, 7.0 and 10. The average for the last category is the most arbitrary. The episode rate of URI among the younger children of the polluted city was 3.1 episodes per person-year and 2.6 in the reference cities, giving a RD of 0.5 episodes per person-year (95% CI: 0.4-0.6) (Table 2). The corresponding figures for the older children were 2.0, 1.7, and 0.3 (0.1-0.5). Accordingly, ER for the younger children in the more polluted area (3.3) compared to those of less polluted area (2.8) gave a RD of 0.5 (0.1 - 0.9) and the corresponding figures for the older children were 2.2, 1.9, and 0.3 (-0.1 0.7). These crude RDs are not likely to be seriously confounded, while the corresponding crude odds ratios did not differ essentially from those adjusted for the confounders in the logistic regression analysis.3 The different analyses do not change qualitatively our findings, which suggest that children's respiratory health can be jeopardized from air pollution in concentrations lower than reported in most earlier studies from Europe. We would also like to point out that the estimated magnitude of the effect, 0.3 to 0.5 extra epiJune 1992, Vol. 82, No. 6
sodes a year, has a considerable public health importance. 0 Jouu J.L Jaakkok MD 0( P. Heinen, MD, DSc Requests for reprints should be sent to Jouni J.K. Jaakkola, MD, Helsinki University of Technology, Kl/Ko 302, Otakaari 4 A, SF02150 Espoo, Finland.
References 1. Miettinen OS. Theoretical epidemiology. P,incpls of occurence research in medicine. New York, NY: John Wiley & Sons; 1985:246-249. 2. Rothman KJ. Modem ep iogy. Boston, Mass: Little, Brown and Company; 1986:24. 3. Jaakkola JJK, Paunio M, Virtanen M, Heinonen OP. Low-level airpollution and upper respiratory infections in children.AmJPublic Health. 1991;81:1060-1063.
Plague Surveillance in Los Angeles County In 1986 Los Angeles County began a plague surveillance program because the number of human plague cases had increased. (uring the past 50 years, all human cases have occurred since 1978, including 3 in 1984.) Reagents and quality control were supplied by the CDC Plague Laboratory. Groups participating in the study included the countyveterinarian, animal shelters, county vector control, the agriculture commissioner, and the California State Polytechnic University, Pomona. Between 1986 and 1990,4,484 animal sera were tested for passive hemagglutination antibodies to Yerismia pestis, with 113 animals having antibody titers of 1:16 or higher. The titers ranged from 1:16 to 1:512, with the most common (modal) titer being 1:32. The largest number of seropositive animals were seen in 1987 (43) and the smallest in 1990 (2). Ground squirrels, dogs, coyotes, and black bears accounted for 109 (96%) of the seropositive animals. Additional seropositive animals included two cats, one fox, one raccoon, and one wild boar. Over half (60) of the seropositive animals were ground squirrels. Of the over 2000 shelter dogs tested, less than 1% were seropositive. Owned dogs were useful in areas of suspected plague epizootics. Two camp dogs were seropositive (1:32, 1:64) in 1987 at Camp Barley Flats, a correctional facility. Yersinia pestis was isolated from a dead ground squirrel found on the premises.
The animals most often seropositive were black bears (75%), wild boar (9%o), coyotes (6%), and ground squirrels (5%).
The seropositive rate for ground squirrels and coyotes was comparable to what was detected 10 years earlier.' Autopsies were performed on most of the coyotes. There were no histopathologic lesions suggestive of plague in any coyote examined. Most coyotes examined were under 1 year of age. Urban coyotes are useftl in plague surveillance of large areas. Wild carnivore provide a practical plague monitoring system. Although black bears and wild boars make good sentinels, they are uncommon in the semi-urban areas of Los Angeles County where most human exposure occurs. Ground squirrels are useful in pinpointing a location where a plague epizootic is occurring or has recently occurred. When ground squirrels are not available, domestic and wild carnivores are useful monitors.2-4 [] C. Pabick RPwn, DVM, MPH P. Eric Hughes, DVM GeorW Ma lsmoto, BA, MT Requests for reprints should be sent to C. Patrick Ryan, County of Los Angeles, Department of Health Services, Comparative Medical and Veterinary Services, 12824 Erickson Avenue, Downey, CA 90242.
References 1. Nelson BC, Madon MB, Tilzer A. The complexities at the interface among domestic/ wild rodents, fleas, pets, and man in urban plague ecology in Los Angeles County, California. In: Proceedings of the Twelfth Vertebrate Pest Conference; 1986:88-96; University of California, Davis. 2. Rust JH, Miller BM, Bahmanyar M, Marshall JD, et al. The role of domestic animals in the epidemiologyof plague. II. Antibodyto
Yeristiair in sera of dogs and cats.Journal of Infectious Diseases 1971;124(5): 527-31. 3. Rust JH, Cavanaugh DC, O'Shita R, Marshall JD. The role of domestic animals in the epidemiology of plague. I. &perunental infection of dogs and cats. Joumal ofInfectious Diseases 1971;124(5):522-26. 4. Nelson JH, Decker MD, Barnes AM, et al. Plague surveillance usingwild boar and wild carivore sentinels.JownalofEnviron,nen-
tal Health 1985;47(6):306-309.
Epidemiologic Studies on Electromagnetic Fields and Cancer Articles in the popular press alleging hazards of electromagnetic fields (EMFs) have contained misconceptions. In particular, in articles by Paul Brodeur in The New Yot*r magazine (and a book dealing with essentially the same information) that state a strong association between exposure to EMFs and cancer, the scientific
American Journal of Public Health 897
Letters to the Editor
evidence was oversimplified, the data were misinterpreted, and the body of work in this area in the scientific literature was ignored (for example, see Foster's review'). Also, the validity of citations of Brodeur's articles in the medical and scientific literature has been questioned.2 Several additional misconceptions have been presented in two more recent articles by Brodeur in The New Yorker. Most of the evidence Brodeur cited for the alleged association comes from epidemiologic studies. In "Annals of Radiation: Calamity on Meadow Street,"3 Brodeur cited a 1979 study containing numerous flaws that he chose to ignore. Michaelson4 and Poole and Trichopoulos5 have presented detailed analyses of some of these flaws. Brodeur also wrote that data from one study6 showed "four times the expected rate of brain cancer in children whose mothers used electric blankets." Brodeur had selected the subgroup with the highest odds ratio in the study, one that represented only 9% of the total population studied for prenatal electric blanket exposure. The odds ratio for association of all prenatal electric blanket exposures with the incidence of childhood cancer was only 1.3. In one study,7 according to Brodeur, "children whose fathers were electricians ran three and a half times the risk of developing tumors of the central nervous system than other children ran." Brodeur insinuated that this finding related to EMF exposure. In that article, however, the ratio was related not to fathers with jobs involving potential EMF exposure, but rather to "fathers who were electricians." This is an important distinction. The odds ratio for jobs in industries involving potential EMF exposure was only 1.6. The authors stated, "the highest risk estimate in our analysis was the odds ratio of 10.0 for construction electricians . . . (who) work largely with unenergized wiring, implying that they have a limited exposure to electromagnetic fields." Brodeur's reference to a cancer cluster in association with EMF exposure lacked a cause-and-effect relationship. An epidemiologist from a state health department has stated that "our investigation of a cluster of brain cancer cases ... was severely hampered by local reaction to the inaccuracies and misconceptions in The New Yorker article."8 Others have expressed similar complaints.8 In "Deartment of Arnpklfcation,"9 Brodeur stated that "eye melanoma .. has been found to be 'notably high for electrical and electronics workers,' who 898 American Journal of Public Health
are known to be exposed to strong magnetic fields." Yet the cited study10 did not mention exposure to EME. Brodeur also stated that "melanoma of the skin is ... prevalent amongworkers in electrical and electronic occupations, and thus associated with exposure to magnetic fields." Occupational titles, however, are a poor means of assessing potential EMF exposure. Brodeur called for several departments of health to conduct full-scale investigations of alleged EMF hazards. Yet it is questionablewhether the money spent on such investigations would be justified. As Weisburger11 has explained, "with limited funds available for serious research efforts, a program on electromagnetic fields and cancer could be counterproductive by diverting effort and money from more relevant research and public information activities." In contrast to Brodeur's claims, the majority of epidemiologic studies do not support the contention that there is an association between EMF exposure and cancer.12 His highly speculative and unsubstantiated claims should not be accepted as representing the scientific literature dealing with EMFs. Public health experts should be aware of these misconceptions and must challenge the appearance of such accounts in both the popular press and in medical and scientific journals. [1 James R. Jauche, PhD Requests for reprints should be sent to James R. Jauchem, Directed Energy Division, Occupational and Environmental Health Directorate, Armstrong Laboratory, Brooks Air Force Base, TX 78235. The opinions are those of the author and do not necessarily state or reflect those of the US government.)
References 1. Foster KR. Book review-Currents of death: Power lines, computer terminals, and the attempt to cover up their threat to your health. IEEE Eng Med Biol Mag.
1990;9(1):89.
2. Jauchem JR. Electromagnetic fields: Is there really a danger? Lancet 1990;336:884. Letter. 3. 7he New Yorker. July 9, 1990. 4. Michaelson SM. Household magnetic fields and childhood leukemia: a critical
analYsis. Pedatrics. 1991;88:630-635.
5. Poole C, Trichopoulos D. Extremely lowfrequency electric and magnetic fields and cancer. Cancer Causes ControL 1991;2: 267-276. 6. Savitz DA, John EM, Kleckner RC. Magnetic field exposure from electric appli-
ances and childhood cancer. Am JEpide-
miot 1990;131:763-773.
7. Johnson CC, Spitz MR. Childhood nervous system tumours: an assessment of
risk associated with paternal occupations involving use, repair or manufacture of electrical and electronic equipment. Int J EpidemnioL 1990;18:756-762. 8. Newman ME. Electromagnetic fields and cancer-Media and public attention affect research.JNatlCancerInst. 1991;83:164166. 9. 7he New Yorker. November 8, 1990. 10. Swerdlow AJ. Epidemiology of eye cancer in adults in England and Wales, 1962-1977. Am JEpideniology. 1983;118:294-300. 11. Weisburger JH. Cancer and electromagnetic fields. Lancet. 1990;336:1259. Letter. 12. JauchemJR, MerrittJH. The epidemiology of exposure to electromagnetic fields: an overview of the recent literature.JClin EpidemioL 1991;44:895-906.
The Correct Use of Growth Charts It is with great interest that I read the article by M. T. Ruel, D. L. Pelletier, J.-P. Habicht, et al., "Comparison between two growth charts in Lesotho" (Am J Public Health. 1991;81:610-615). I was surprised to see that both emphasize percentage deficit, which is taken as a percentage of the median of the reference population. My experience in different places (most recently in Indonesia) is that health workers feel that, on a Road-toHealth (RHT) chart that carries the top of the "green" at the male median W/Age, anyone who falls beyond the top line (i.e., in the white part) is "abnormal." I am very glad that at least the RHT was chosen as the more effective chart and that both mothers and health workers had a better understanding of the process indicated on the card. As it is, teaching is usually done the wrong way round: the chart should not be an initial indicator but a tool for the evaluation of growth; the advice given is the most important. The Guideline should come first, with the feeding advice, then the weighing to see if the mother's efforts have bome fruit-this is the original process of child health care. The interview with the mother-not the chart-gives the answers regarding good or indifferent care. Many children bom at or above the chart median can stay there without any problem, but health workers are quite happy if they "flatten off" into the "green" until they approach the 80%o line, and in some countries supplementary feeding may start only at the 60%o line. I wonder why the Catholic Relief Service Food and Nutrition Programme still uses the GS card with its unphysiologic implications? Especially in Africa, one would not expect the well fed to deviate too farfrm the National Center for Health Statistics distribution-
June 1992, Vol. 82, No. 6
