Maternal ingestion of radon-222 in drinking water and the absorbed radiation dose to the embryo

Maternal ingestion of high concentrations of radon-222 (Rn-222) in drinking during pregnancy may pose a significant radiation hazard to the developing embryo. The effects of ionizing radiation to the embryo and fetus have been the subject of research, analyses, and the development of a number of radiation dosimetric models for a variety of radionuclides. Currently, essentially all of the biokinetic and dosimetric models that have been developed by national and international radiation protection agencies and organizations recommend calculating the dose to the mother's uterus as a surrogate for estimating the dose to the embryo. Heretofore, the traditional radiation dosimetry models have neither considered the embryo a distinct and rapidly developing entity, the fact that it is implanted in the endometrial layer of the uterus, nor the physiological interchanges that take place between maternal and embryonic cells following the implantation of the blastocyst in the endometrium. The purpose of this research was to propose a new approach and mathematical model for calculating the absorbed radiation dose to the embryo by utilizing a semiclassical treatment of alpha particle decay and subsequent scattering of energy deposition in uterine and embryonic tissue. The new approach and model were compared and contrasted with the currently recommended biokinetic and dosimetric models for estimating the radiation dose to the embryo. The results obtained in this research demonstrate that the estimated absorbed dose for an embryo implanted in the endometrial layer of the uterus during the fifth week of embryonic development is greater than the estimated absorbed dose for an embryo implanted in the uterine muscle on the last day of the eighth week of gestation. This research provides compelling evidence that the recommended methodologies and dosimetric models of the Nuclear Regulatory Commission and International Commission on Radiological Protection employed for calculating the radiation dose to the embryo from maternal intakes of radionuclides, including maternal ingestion of Rn-222 in drinking water would result in an underestimation of dose. ^

REPRODUCTIVE PERFORMANCE IN THE DES-EXPOSED DAUGHTERS

This research examined the relation between prenatal exposure to diethylstilbestrol (DES) and subsequent reproductive performance in females. Although previous studies have agreed that unfavorable pregnancy outcomes (spontaneous abortions, stillbirths, ectopic pregnancies, and premature births) occur with greater frequency in the exposed as compared to unexposed women, the role of exposure to DES in-utero on subsequent fertility (pregnancy achievement) remains controversial. Also, the possibility that the reproductive dysfunction reported in exposed women might be due to familial predisposition to reproductive dysfunction rather than to DES exposure has not been examined heretofore.^ The purposes of the research were to: (1) measure the overall differences in rates of live births between exposed and unexposed women; (2) determine if infertility or early unrecognized spontaneous miscarriages (as opposed to recognized fetal death) contributes to poor reproductive performance in the exposed; and (3) determine if constitutional predisposition contributes to poor reproductive performance in exposed daughters.^ The study population comprised those participants in the National Cooperative Diethylstilbestrol Adenosis (DESAD) Project who were identified through review of prenatal records. Birth interval curves (survival analyses) were used to compare the reproductive performance of exposed daughters and unexposed women. Birth interval curves were also constructed for unexposed siblings (of exposed participants) and unexposed nonsiblings to determine the role of constitutional predisposition in the reproductive performance of exposed daughters.^ The DES-daughters, as compared to unexposed women, were found to be at a reproductive disadvantage when the overall differences in rates of live births were compared.^ When the differences in rates of live births due specifically to infertility or early unrecognized spontaneous miscarriages (as opposed to recognized fetal death) were examined, the exposed maintained the reproductive disadvantage. This analysis was suggestive but not statistically significant for the first-birth-interval and was neither suggestive nor significant in the second-birth-interval. (Abstract shortened with permission of author.) ^

Design of a systematic approach to workplace exposure medical surveillance protocols

Current toxic tort cases have increased national awareness of health concerns and present an important avenue in which public health scientists can perform a vital function: in litigation, and in public health initiatives and promotions which may result. This review presents a systematic approach, using the paradigm of interactive public health disciplines, for the design of a matrix framework for medical surveillance of workers exposed to toxic substances. The matrix framework design addresses the required scientific bases to support the legal remedy of medical monitoring for workers injured as a result of their exposure to toxic agents. A background of recent legal developments which have a direct impact on the use of scientific expertise in litigation is examined in the context of toxic exposure litigation and the attainment of public health goals. The matrix model is applied to five different workplace exposures: dental mercury, firefighting, vinyl chloride manufacture, radon in mining and silica. An exposure matrix designed by the Department of Energy for government nuclear workers is included as a reference comparison to the design matrix. ^

Family stress, coping, communication, and adaptation in unintended adolescent pregnancy

Objective. This study examines post-crisis family stress, coping, communication, and adaptation using the Double ABC-X Model of Family Adaptation in families with a pregnant or postpartum adolescent living at home. ^ Methods. Ninety-eight pregnant and parenting adolescents between ages 14 and 18 years (Group 1 at 20 or more weeks gestation; Group 2 at delivery and 8 weeks postpartum) and their parent(s) completed instruments congruent with the model to measure family stress, coping, communication, and adaptation. Descriptive family data was obtained. Mother-daughter data was analyzed for differences between subjects and within subjects using paired t-tests. Correlational analysis was used to examine relationships among variables. ^ Results. More than 90% of families were Hispanic. There were no significant differences between mother and daughter mean scores for family stress or communication. Adolescent coping was not significantly correlated to family coping at any interval. Adolescent family adaptation scores were significantly lower than mothers' scores at delivery and 8 weeks postpartum. Mean individual ratings of family variables did not differ significantly between delivery and 8 weeks postpartum. Simultaneous multiple regression analysis showed that stress, coping, and communication significantly influenced adaptation for mothers and daughters at all three intervals. The relative contributions of the three independent variables exhibited different patterns for mothers and daughters. Parent-adolescent communication accounted for most of the variability in adaptation for daughters at all three intervals. Daughters' family stress ratings were significant for adaptability (p = .01) during the pregnancy and for cohesion (p = .03) at delivery. Adolescent coping (p = .03) was significant for cohesion at 8 weeks postpartum. Family stress was a significant influence at all three intervals for mothers' ratings of family adaptation. Parent-adolescent communication was significant for mother's perception of both family cohesion (p < .001) and adaptability (p < .001) at delivery and 8 weeks, but not during pregnancy. ^ Conclusions. Mothers' and daughters' ratings of family processes were similar regarding family stress and communication, but were significantly different for family adaptation. Adolescent coping may not reflect family coping. Family communication is a powerful component in family functioning and may be an important focus for interventions with adolescents and parents. ^

Incidence of breast cancer in first-degree female relatives of men with newly diagnosed prostate cancer

Prostate cancer is the most common incident cancer and the second leading cause of death in men in the United States. Although numerous attempts have been made to identify risk factors associated with prostate cancer, the results have been inconsistent and conflicting. The only established risk factors are age and ethnicity. A positive family history of prostate cancer has also been shown to increase the risk two- to three-fold among close relatives.^ There are several similarities between breast and prostate cancer that make the relationship between the two of interest. (1) Histologically, both cancers are predominantly adenocarcinomas, (2) both organs have a sexual and/or reproductive role, (3) both cancers occur in hormone-responsive tissue, (4) therapy often consists of hormonal manipulation, (5) worldwide distribution patterns of prostate and breast cancer are positively correlated.^ A family history study was conducted to evaluate the aggregation of prostate cancer and co-aggregation of breast cancer in 149 patients referred to The University of Texas, M.D. Anderson Cancer Center with newly diagnosed prostate cancer. All patients were white, less than 75 years of age at diagnosis and permanent residents of the United States. Through a personal interview with the proband, family histories were collected on 1,128 first-degree relatives. Cancer diagnoses were verified through medical records or death certificate. Standardized incidence ratios were calculated using a computer program by Monson incorporating data from Connecticut Tumor Registry.^ In this study, familial aggregation of prostate cancer was verified only among the brothers, not among fathers. Although a statistically significant excess of breast cancer was not found, the increased point estimates in mothers, sisters and daughters are consistent with a co-aggregation hypothesis. Rather surprising was the finding of a seven-fold increased risk of prostate cancer and a three-fold increased risk of breast cancer among siblings in the presence of a maternal history of any cancer. Larger family history studies including high risk (African-Americans) and lower-risk groups (Hispanics) and incorporating molecular genetic evaluations should be conducted to determine if genetic differences play a role in the differential incidence rates across ethnic groups. ^

Spatial distribution of orofacial cleft birth defects and uranium-radium concentrations in tap water in Atascosa, Bee, Brooks, Calhoun, Duval, Goliad, Hidalgo, Jim Hogg, Jim Wells, Karnes, Kleberg, Live Oak, McMullen, Nueces, San Patricio, Refugio, Starr, Victoria, Webb, and Zavala Counties, Texas

Background Past and recent evidence shows that radionuclides in drinking water may be a public health concern. Developmental thresholds for birth defects with respect to chronic low level domestic radiation exposures, such as through drinking water, have not been definitely recognized, and there is a strong need to address this deficiency in information. In this study we examined the geographic distribution of orofacial cleft birth defects in and around uranium mining district Counties in South Texas (Atascosa, Bee, Brooks, Calhoun, Duval, Goliad, Hidalgo, Jim Hogg, Jim Wells, Karnes, Kleberg, Live Oak, McMullen, Nueces, San Patricio, Refugio, Starr, Victoria, Webb, and Zavala), from 1999 to 2007. The probable association of cleft birth defect rates by ZIP codes classified according to uranium and radium concentrations in drinking water supplies was evaluated. Similar associations between orofacial cleft birth defects and radium/radon in drinking water were reported earlier by Cech and co-investigators in another of the Gulf Coast region (Harris County, Texas).50, 55 Since substantial uranium mining activity existed and still exists in South Texas, contamination of drinking water sources with radiation and its relation to birth defects is a ground for concern. ^ Methods Residential addresses of orofacial cleft birth defect cases, as well as live births within the twenty Counties during 1999-2007 were geocoded and mapped. Prevalence rates were calculated by ZIP codes and were mapped accordingly. Locations of drinking water supplies were also geocoded and mapped. ZIP codes were stratified as having high combined uranium (≥30μg/L) vs. low combined uranium (<30μg/L). Likewise, ZIP codes having the uranium isotope, Ra-226 in drinking water, were also stratified as having elevated radium (≥3 pCi/L) vs. low radium (<3 pCi/L). A linear regression was performed using STATA® generalized linear model (GLM) program to evaluate the probable association between cleft birth defect rates by ZIP codes and concentration of uranium and radium via domestic water supply. These rates were further adjusted for potentially confounding variables such as maternal age, education, occupation, and ethnicity. ^ Results This study showed higher rates of cleft births in ZIP codes classified as having high combined uranium versus ZIP codes having low combined uranium. The model was further improved by adding radium stratified as explained above. Adjustment for maternal age and ethnicity did not substantially affect the statistical significance of uranium or radium concentrations in household water supplies. ^ Conclusion Although this study lacks individual exposure levels, the findings suggest a significant association between elevated uranium and radium concentrations in tap water and high orofacial birth defect rates by ZIP codes. Future case-control studies that can measure individual exposure levels and adjust for contending risk factors could result in a better understanding of the exposure-disease association.^