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Letters are welcomed and will be published, iffound suitable, as space permits. The editors reserve the right to edit and abridge letters, to publish replies, and to solicit responses from authors and others. Letters should be submitted in duplicate, double-spaced (including references), and generally should not exceed 400 words.
Caution Against Use of Extrapolated Risk Estimate We would like to comment on the risks implied by A. P. Jacobson, et al, in their paper "Contamination of the Home Environment by Patients Treated with 1-131: Initial Results," [AJPH Vol. 68, No. 3, pg. 225-230]. We feel that the authors errored in determining the risks of thyroid cancer by using the maximum dose received by one individual and calculating a risk on the basis of every individual receiving this dose. In addition, we would like to caution against the use of the extrapolated risk estimate, itself, in determining cancer incidence. The BEIR best risk estimate to children as the authors point out is 1.6 to 9.3 new cases per year per 106 people-rad. Using the authors' data, excluding only the erroneous external exposure of 2200 mrads, we calculated an average external plus internal thyroid exposure of 219 mrads. This would represent a risk of .35 to 2.0 cases per 106 people/year or a 3 to 20 per cent increase over the naturally occurring incidence rate for this group, not a doubling as the authors state. The authors point out that 700,000 thyroid diagnoses by 1-131 were performed in 1974. However, only about 10 per cent of these had therapeutic procedures with the 1-131 activities of concern. Assuming two children per family, this represents a risk to 140,000 children a year or a total upper risk estimate of .3 new AJPH September, 1978, Vol. 68, No. 9
Letters to the Editor cases per year compared to the natural incidence rate of 2200 per year. We encourage the use of protective measures in order to keep exposures to relatives and all persons as low as practical. However, it must be stressed that risk estimates extrapolated to low doses are of questionable value, at best, in assessing the true low dose risks and should be used strictly for assessing radiation protection limits. RichardJ. Petersen, MD Stanley S. Jaeger, MS Bishop Clarkson Memorial Hospital Dewey Avenue at 44th Omaha, NE 68105
Authors' Response The comments by Jaeger and Petersen point out to us the need to caution against the possible errors of extrapolation even more carefully than we did (our article, page 229, second paragraph, right hand column). A. P. Jacobson, PhD Associate Professor of Environmental and Industrial Health University ofMichigan School of Public Health Ann Arbor 48109
On Definition of Anemia in Pregnancy The article of Owen and Owen (AJPH 67:865-866, 1977) and subsequent discussion in the Letters to the Editor column by Buttery, and Owen, (AJPH 68:174, 1978) raised important issues regarding racial factors in the definition of anemia. Statistical definitions of normal hemoglobin may vary between races. Garn, et al,1 have recently reported Black-White differ-
ences in hemoglobin concentrations during pregnancy, and Dallman, et al,2 have recently confirmed Black-White differences in hemoglobin during childhood. In 1977 we completed a study of maternal and child health care indices on 500 consecutive pregnancies, in mothers from both the indigent and non-indigent populations, who presented to maternal and child health care clinics in Davao City, Philippines. Our data illustrated the importance of racial considerations in the determination of anemia levels with respect to OrientalOccidental populations.3 Anemia is a high-risk complication of pregnancy.4 Using a modification of the maternal and child health care index of Nesbitt and Aubry,5 no association was seen between Asian mothers with mild anemia (Hgb of 10-11 gms/dI) on initial prenatal examination and those who subsequently developed high-risk pregnancy complications and poor pregnancy outcome. However, there were statistically significant correlations (p < 0.05) between Asian mothers with moderate (Hgb 9-10 gms/ dl) or severe (Hgb < 9 gms/dl) anemia, and those who developed high-risk pregnancy and poor pregnancy outcome. These findings are in contrast to those in Western populations where mild as well as moderate and severe anemia were related to pregnancy outcome.
Furthermore, there were no differences in the prevalence of mild anemia between the indigent and nonindigent Asian populations on initial prenatal examination, while prevalence of moderate and severe anemia was two times greater in the indigent than in the non-indigent population due to socioeconomic considerations. If mild (Hgb 10-11 gms/dl) anemia had functional meaning within the Asian population, one would expect significant dif907
Letters are welcomed and will be published, iffound suitable, as space permits. The editors reserve the right to edit and abridge letters, to publish replies, and to solicit responses from authors and others. Letters should be submitted in duplicate, double-spaced (including references), and generally should not exceed 400 words.
Caution Against Use of Extrapolated Risk Estimate We would like to comment on the risks implied by A. P. Jacobson, et al, in their paper "Contamination of the Home Environment by Patients Treated with 1-131: Initial Results," [AJPH Vol. 68, No. 3, pg. 225-230]. We feel that the authors errored in determining the risks of thyroid cancer by using the maximum dose received by one individual and calculating a risk on the basis of every individual receiving this dose. In addition, we would like to caution against the use of the extrapolated risk estimate, itself, in determining cancer incidence. The BEIR best risk estimate to children as the authors point out is 1.6 to 9.3 new cases per year per 106 people-rad. Using the authors' data, excluding only the erroneous external exposure of 2200 mrads, we calculated an average external plus internal thyroid exposure of 219 mrads. This would represent a risk of .35 to 2.0 cases per 106 people/year or a 3 to 20 per cent increase over the naturally occurring incidence rate for this group, not a doubling as the authors state. The authors point out that 700,000 thyroid diagnoses by 1-131 were performed in 1974. However, only about 10 per cent of these had therapeutic procedures with the 1-131 activities of concern. Assuming two children per family, this represents a risk to 140,000 children a year or a total upper risk estimate of .3 new AJPH September, 1978, Vol. 68, No. 9
Letters to the Editor cases per year compared to the natural incidence rate of 2200 per year. We encourage the use of protective measures in order to keep exposures to relatives and all persons as low as practical. However, it must be stressed that risk estimates extrapolated to low doses are of questionable value, at best, in assessing the true low dose risks and should be used strictly for assessing radiation protection limits. RichardJ. Petersen, MD Stanley S. Jaeger, MS Bishop Clarkson Memorial Hospital Dewey Avenue at 44th Omaha, NE 68105
Authors' Response The comments by Jaeger and Petersen point out to us the need to caution against the possible errors of extrapolation even more carefully than we did (our article, page 229, second paragraph, right hand column). A. P. Jacobson, PhD Associate Professor of Environmental and Industrial Health University ofMichigan School of Public Health Ann Arbor 48109
On Definition of Anemia in Pregnancy The article of Owen and Owen (AJPH 67:865-866, 1977) and subsequent discussion in the Letters to the Editor column by Buttery, and Owen, (AJPH 68:174, 1978) raised important issues regarding racial factors in the definition of anemia. Statistical definitions of normal hemoglobin may vary between races. Garn, et al,1 have recently reported Black-White differ-
ences in hemoglobin concentrations during pregnancy, and Dallman, et al,2 have recently confirmed Black-White differences in hemoglobin during childhood. In 1977 we completed a study of maternal and child health care indices on 500 consecutive pregnancies, in mothers from both the indigent and non-indigent populations, who presented to maternal and child health care clinics in Davao City, Philippines. Our data illustrated the importance of racial considerations in the determination of anemia levels with respect to OrientalOccidental populations.3 Anemia is a high-risk complication of pregnancy.4 Using a modification of the maternal and child health care index of Nesbitt and Aubry,5 no association was seen between Asian mothers with mild anemia (Hgb of 10-11 gms/dI) on initial prenatal examination and those who subsequently developed high-risk pregnancy complications and poor pregnancy outcome. However, there were statistically significant correlations (p < 0.05) between Asian mothers with moderate (Hgb 9-10 gms/ dl) or severe (Hgb < 9 gms/dl) anemia, and those who developed high-risk pregnancy and poor pregnancy outcome. These findings are in contrast to those in Western populations where mild as well as moderate and severe anemia were related to pregnancy outcome.
Furthermore, there were no differences in the prevalence of mild anemia between the indigent and nonindigent Asian populations on initial prenatal examination, while prevalence of moderate and severe anemia was two times greater in the indigent than in the non-indigent population due to socioeconomic considerations. If mild (Hgb 10-11 gms/dl) anemia had functional meaning within the Asian population, one would expect significant dif907
