HEALTH CONSULTATION
Health Outcome Data Evaluation
KELLY AIR FORCE BASE
SAN ANTONIO, BEXAR COUNTY, TEXAS
Health outcomes selected for evaluation were based on community concerns and biological plausibility. During several site visits to Kelly Air Force Base in San Antonio, Texas, ATSDR staff members discussed health concerns with community residents. Many residents expressed concern about elevated cancer rates and birth defects. Citizens also expressed concerned about reports of lead found in soil samples taken from the neighborhood and the effects that exposure to lead may have on their children. This health consultation addresses these concerns.
Health outcome data is evaluated if a completed exposure pathway exists for the chemical or chemicals suspected of causing the health outcome of concern. When a contaminant of concern has been identified as a carcinogen, specific types of cancers which may be related to the contaminant are usually selected for evaluation. At Kelly, we have identified hexavalent chromium and volatile organic compounds (VOCs) such as tetrachloroethylene and benzene in air as a pathway of exposure. For cancer, the health outcomes we considered included cancer of the kidney, liver, lung, cervix, bladder, and leukemia. We also examined all reportable birth defects and low birth weight babies. The majority of the health outcome data analyses focused on zip code areas 78211, 78228, and 78237.
The evaluation of health outcome data helps to provide a general picture of the health of a community, and it may help to identify or confirm the presence of excess disease or illness in a community. However, elevated rates of a particular disease may not necessarily be caused by hazardous substances in the environment. Other factors, such as socioeconomic status, occupation, and lifestyle, also may influence the development of disease. In contrast, a contaminant can contribute to illness or disease without this being reflected in the available health outcome data.
II. INTERPRETING HEALTH OUTCOME DATA
To determine whether there is an excess of a particular disease or health condition, we compare the observed number of cases in the population living in the area of concern to an "expected" number of cases determined from a standard population. For cancer, we examined the ratio of observed-to-expected number of cases (incidence) or deaths (mortality), and the information was further standardized to eliminate possible effects due to race, sex, and age. These ratios are referred to as the standardized incidence ratio (SIR) or standardized mortality ratio (SMR). The type of ratio used depends on the type of health data to which one is referring. For birth defects and low birth weight babies, we divided the number of observed cases by the number expected, producing an observed-to-expected ratio (O:E ratio).
An O:E ratio of 1.0 indicates that the number of cases observed in the population being evaluated is equal to the number of cases expected based on the rate of disease in the comparison population. A ratio greater than 1.0 indicates that more cases occurred than expected; and a ratio less than 1.0 indicates that fewer cases occurred than expected. Accordingly, a ratio of 1.5 is interpreted as 50% more cases than expected; and a ratio of 0.9 indicates 10% fewer cases than would be expected.
Caution should be exercised, however, when interpreting these ratios. The interpretation of a ratio depends on both the value of the ratio and the numbers used to compute the ratio. Two ratios can have the same size but be interpreted differently. For example, a ratio of 1.5 based on 2 expected cases and 3 observed cases indicates a 50% excess in cancer, but the excess is actually only 1 case. However, a ratio of 1.5 based on 200 expected cases and 300 observed cases represents the same 50% excess in cancer, but because the ratio is based upon a greater number of cases, the estimate is less likely to be attributable to chance. It is very unlikely that 100 excess cases of cancer would occur by chance alone. However, a single excess case very easily could be due to chance occurrence.
A certain amount of chance variation can be expected when looking at the occurrence of different health conditions in communities, and statisticians have developed methods to take this into account. One method is to calculate a 95% confidence interval (CI) for the O:E ratio. The 95% CI is the range of estimated ratio values that has a 95% probability of including the true ratio for the population. The confidence interval is a statistical measure of the precision of the risk estimate.
"Statistically significant" means there is less than 5% chance that the observed difference is merely the result of random fluctuation in the number of observed cancer cases. For example, if the confidence interval does not include 1.0 and the interval is below 1.0, then the number of cases is significantly lower than expected. Similarly, if a confidence interval does not include 1.0 and the interval is above 1.0, then there is a significant excess in the number of cases. If the confidence interval includes 1.0, then the true ratio may be 1.0, and it cannot be concluded with sufficient confidence that the observed number of cases reflects a real excess or deficit. As long as the 95% confidence interval contains 1.0, that indicates that the ratio is still within the range one might expect based on the disease experience of the comparison population. However, if either the upper or lower bound of the confidence interval is 1.0, it is considered of borderline statistical significance. This means that the ratio is close to being statistically significant and that the number of cases was either higher or lower than expected.
In addition to the number of cases, the width of the confidence interval also reflects the precision of the ratio estimate. For example, a narrow confidence interval (e.g., 1.03-1.15) indicates that the population's size was sufficiently large to generate a fairly precise estimate of the ratio. A wide interval (e.g., 0.85-4.50) indicates far less precision, and more uncertainty, in the calculated ratio.
All cancer data were provided by the Cancer Registry Division (CRD) of the Texas Department of Health. The CRD maintains cancer incidence and mortality data for the state of Texas. Cancer incidence data are acquired under the Texas Cancer Incidence Reporting Act (Chapter 82, Health and Safety Code), which requires every general and special hospital, clinical laboratory, and cancer treatment center to report all cases of cancer to the CRD. Every person, inpatient or outpatient, diagnosed with or treated for cancer must be reported to the CRD. Although the CRD is a passive registry that relies on facilities to supply the information, it monitors the number of expected reports from each institution and contacts those facilities that fail to report. To ensure that reported data are complete and accurate, CRD staff members perform case-finding and other quality control checks at these institutions. The CRD has determined that for Public Health Region 8, which includes San Antonio, cancer incidence reporting is 90%-95% complete for the years 1990-1994. Cancer mortality data is obtained by CRD from death certificate information maintained by the Bureau of Vital Statistics. The CRD conducted an analysis of both cancer incidence (1990-1994) and cancer mortality data (1991-1995) for three zip code areas around Kelly Air Force Base (78211, 78228, and 78237).
After receiving the petition to perform a public health assessment on neighborhoods north and southeast of Kelly Air Force Base, ATSDR requested that the CRD evaluate rates of cancers of the colon, pancreas, lung, prostate, breast, and leukemia in zip code areas 78211 and 78237. This information was used only to give a general idea of the rates of cancer in these communities and the results from this evaluation are presented in Appendix A.
The CRD evaluated cancer incidence data for the period 1990-1994 for San Antonio zip code areas 78211, 78237, and 78228 for the following cancer sites: liver, lung, cervix, bladder, kidney, and leukemia. Data were initially evaluated using race-, sex-, and age-specific cancer incidence rates published by the California Cancer Registry. Statewide cancer incidence data for Texas were not available and the California Cancer Registry had Hispanic cancer rates which could be used for comparison. During the course of the analyses, statewide cancer incidence data became available for Texas and the analyses were updated to include the Texas comparison population. These results are presented in this section. The results from the initial analysis using California rates as the comparison population are included in Appendix B.
During the period 1990-1994, the number of cases observed for cancer of the liver, lung, bladder, kidney, and leukemia were close to the number expected among males and females in zip code 78211 (Table 1). The number of cases observed for cervical cancer among females was also close to the number expected in this area during this time period. In zip code 78228, the number of observed cases of bladder cancer and leukemia among males and females were close to the number expected, as were the number of cases observed for lung, cervical, and kidney cancer among females (Table 2). A significant excess of liver cancer among males was observed. A higher than expected number of kidney cancer cases and a lower than expected number of lung cancer cases was observed among males in this zip code, which was of borderline statistical significance. In zip code 78237, the number of cases observed for lung, bladder and kidney cancer, as well as leukemia, was close to the number expected among males (Table 3). However, a significant excess of liver cancer was observed among males in this zip code area. The number of cases observed for cancer of the liver, lung, and bladder were close to the number expected among females in this zip code area. A significant excess of leukemia among females was observed as was a higher than expected number of kidney and cervical cancer cases, although these elevations were of borderline statistical significance.
ATSDR compares mortality and incidence data for indications of reporting consistency. Using death certificate information, the CRD also evaluated cancer mortality for the same cancer sites for the three zip code areas of concern for the period 1991-1995 (Tables 4-6). During this period, a significant excess of liver cancer deaths was observed among males in zip codes 78228 and 78237. During the same period of time, a significant excess of liver cancer deaths was observed among females in zip codes 78211 and 78237. In zip code 78228, the number of lung cancer cases in males was significantly lower than expected. A higher than expected number of leukemia cases was observed among males in zip code 78237, although the elevation was of borderline statistical significance.
Additional Liver Cancer Analysis
Because of the increased occurrence of liver cancer in the initial three zip code areas, ATSDR requested that the CRD evaluate the incidence and mortality data for liver cancer in ten additional zip code areas surrounding Kelly Air Force Base in order to determine if there were an excess of liver cancer cases. Incidence data were initially evaluated using race-, sex-, and age-specific cancer incidence rates published by the California Cancer Registry because statewide cancer incidence data for Texas was not available at the time this analysis was conducted. Once statewide cancer incidence data for Texas became available, the analyses were conducted using these rates. The results from the analysis using California as the comparison population are included in Appendix B.
An additional five zip code areas were evaluated when conducting the analysis of liver cancer rates in the area using Texas incidence data but not evaluated when conducting the analysis of liver cancer mortality. For the sake of consistency, Tables 7 and 8 include the results from the same zip code areas. The results from the five additional zip code areas are included in Appendix C.
The analysis of incidence data using Texas as the comparison population for the ten additional zip code areas during the period 1990-1994 indicates a statistically significant excess of liver cancer among males in the 78201, 78205, and 78227 zip code areas (Table 7). A higher than expected number of liver cancer cases was observed among males in zip code 78207, although this excess was of borderline statistical significance. Among females in the study area during the same time period, no statistically significant excess of liver cancer was observed. However, a higher than expected number of liver cancer cases was observed among females in zip code 78207 and 78221, although these excesses were of borderline statistical significance.
The analysis of mortality data for this area during the period 1991-1995 also indicates a statistically significant excess of liver cancer among the males in the 78201, 78204, and 78207 zip code areas and females in the 78242 zip code (Table 8). A higher than expected number of liver cancer deaths in males was observed in zip code 78227 and in females in zip code areas 78207, 78221, and 78226, although the elevations were of borderline statistical significance.
In order to examine cancer incidence in other areas surrounding Kelly Air Force Base, ATSDR requested that the CRD evaluate incidence data for cancer of the liver, lung, cervix, bladder, kidney, and leukemia in the zip code areas 78201, 78204, 78205, 78207, 78221, 78224, 78225, 78226, 78227, and 78242 during the period 1990-1994. The results from these analyses are presented in Appendix D.
Overall, liver cancer rates are elevated in many zip code areas surrounding Kelly Air Force Base; however the reason for these elevations is unknown. The data available to the Texas Cancer Registry regarding individuals who have been diagnosed with liver cancer is limited. Information is not available concerning known risk factors associated with liver cancer, or if occupations had exposed individuals to chemicals that are known liver carcinogens.
The analysis of liver cancer mortality found a significant excess among males and females in two zip code areas. Only one zip code area had a significant excess of liver cancer deaths for both males and females. While the number of liver cancer deaths was elevated, mortality can be affected by several factors including socioeconomic status, access to medical care, and stage of disease at diagnosis. Additionally, the liver is a common site of metastasis for tumors originating in other organs. Metastasis is the spread of disease from one part of the body to another unrelated to it. Death certificates and hospital charts cannot always be relied on to accurately distinguish primary from secondary (metastatic) tumors, making the interpretation of these results difficult.
IV. GENERAL FACTS ABOUT CANCER
Almost everyone alive today will be affected by cancer, either personally or because friends and family members contract the disease. Approximately two out of every five persons will develop some type of cancer in their lifetime. Furthermore, cancer is not one disease, but many different diseases. Different types of cancer are generally thought to have different causes. In Texas, as in the United States as a whole, cancer is the second leading cause of death, exceeded only by heart disease. In 1996, 31,969 Texans died of cancer. Sixty-five percent of these deaths were in persons 65 years of age or older.
The incidence of cancer varies by race/ethnicity, gender, the type of cancer, geographic distribution, population under study, and a variety of other factors. Scientific studies have identified a number of factors for various cancers which may increase an individual's risk of developing a specific type of cancer. Some risk factors cannot be influenced by individual behavior, but many can. General cancer risk factors include heredity, geographic area, diet, environmental causes, tobacco smoke, sexual practices, and alcohol consumption.
The term "primary liver cancer" refers to any malignant tumor arising in the liver itself, not to a cancer that originates elsewhere and spreads, or metastasizes, to the liver. Hepatitis B infection is the most important risk factor in the occurrence of liver cancer worldwide. However, it is usually necessary for infection with hepatitis B to occur early in life in order for liver cancer to develop; it rarely develops in individuals who become infected in adulthood. Males are at much greater risk (twofold to sevenfold higher) for developing liver cancer than females. Also, individuals with cirrhosis of the liver resulting from hepatitis B are at much higher risk of developing liver cancer than those with less severe liver disease. Cirrhosis refers to the consequences of chronic liver injury, that is, extensive scarring of the liver in which the scar tissue surrounds "nodules" of regenerating liver tissue. Some of the causes of cirrhosis are alcohol abuse, chronic hepatitis, prolonged obstruction to the outflow of the bile from the liver, and some viral forms of autoimmune liver disease. Recently, infection with the hepatitis C virus has been strongly linked with liver cancer.
Exposure to some chemicals and toxins can lead to liver cancer. Perhaps the best known and extensively studied is aflatoxin. Aflatoxin, a common mold found in poorly stored peanuts and other foods, readily causes liver cancer in laboratory animals and, in humans, may potentiate the cancer-causing effects of hepatitis B infection.
Some forms of inherited metabolic diseases may predispose individuals to liver cancer. The most common of these is hemochromatosis or "iron overload," a disorder of iron metabolism that results in an excessive accumulation of iron in the body. If untreated, iron accumulation leads to cirrhosis and the development of liver cancer.
Other risk factors thought to be associated with liver cancer include alcohol intake, smoking, use of anabolic steroids, and the use of oral contraceptives.
Kidney cancer accounts for 2% of all new cancers each year in the United States. Studies have shown that cigarette smoking increases the risk of kidney cancer as does high relative weight or obesity. Early studies noted the association of obesity and kidney cancer among women; however, more recent studies have also found an increased risk among overweight men. Some studies have found death from kidney cancer to be elevated among asbestos-exposed workers and among coke-oven workers in steel plants.
Leukemia is cancer of the blood-forming cells. It occurs when immature or mature cells multiply in an uncontrolled manner in the bone marrow. There are four types of leukemia: acute lymphocytic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and chronic myelogenous leukemia (CML). Each type of leukemia can have a different etiology and a different prognosis.
In 1993, about 29,000 new cases of leukemia were diagnosed in the United States, representing about 2.4% of all new cancer cases in that year. Leukemia occurs slightly more often in whites than in blacks and in males more often than females. The incidence of leukemia also varies by age. Leukemia accounts for nearly one-third of all children's cancers, but it actually affects far more adults than children. Acute lymphocytic leukemia occurs predominantly in young children and in adults age 65 and older; acute myeloid leukemia occurs in infants, adolescents, and older people, but is unusual in young children (ages 2 to 10). Only 5% of childhood leukemia cases are chronic, and virtually all of these are chronic myeloid leukemia. Chronic lymphocytic leukemia almost never occurs in children and is rare before age 30; 60 years is the average age at diagnosis. Chronic myeloid leukemia is uncommon below the age of 20; half of all CML patients are over age 67.
Certain factors are known are known to increase the risk of developing the disease. Among these are exposure to radiation, heredity, congenital factors, chemicals (benzene), drugs (chloramphenicol, phenylbutazone), and viruses (human T-lymphotrophic virus type I or HTLV-I).
The two major risk factors for cancer of the cervix are sexual intercourse at an early age and multiple sex partners. More than 90% of all cervical cancer cases are due to a sexually transmitted human papillomavirus infection of the cervix.
In a number of studies, cigarette smoking has been found to increase the risk of cervical cancer; especially among long-term or high-intensity smokers. Choice of contraceptive method also appears to affect the risk of cervical cancer. There is increasing evidence that nutritional factors may play a role in cervical disease. Several studies suggest that low intake of either vitamin C or beta carotene may be associated with elevations in risk, although this has not always been found. Deficiency in folacin (one of the B complex vitamins) has also been proposed as a risk factor, especially among oral contraceptive users whose stores of this vitamin are depleted.
All data relating to birth defects were provided by the Texas Department of Health (TDH) Birth Defects Monitoring Division (TBDMD) and the TDH Bureau of Vital Statistics. Birth defects were identified by examining three types of vital record certificates: live birth certificates, fetal death certificates, and infant death certificates. Each type of vital record contains information on birth defects, and the fetal and infant death certificates also contain information on the cause(s) of death. The TBDMD began active surveillance for birth defects in the San Antonio in January 1997.
Texas requires that birth certificates to be filled out for all live births and that the certificates be filed with the state within 5 days of the birth. Birth defects are reported on birth certificates through the use of check boxes. The physician has the choice of 24 boxes. Twenty-two boxes list specific categories of birth defects; there is one check box for "other" defects, and one check box for "none".
A fetal death certificate must be filed for any stillborn infant of 20 weeks or more gestation. Birth defects are also reported on fetal death certificates through the use of check boxes. The physician has the choice of the same 24 boxes.
Infant deaths are defined as the death of a baby less than one year of age. The same death certificate is used to record all deaths in Texas, regardless of the age at death. Death certificates list the International Classification of Disease 9th Revision (ICD-9) code for all causes of death, both the immediate cause and the underlying cause(s). The ICD-9 codes are a system of numerical codes for specific diseases and health conditions. Birth defects listed among the cause(s) of death are found coded by specific ICD-9 codes.
For this health assessment, we defined a case as an infant or fetus who
1) was delivered between January 1, 1990, and December 31, 1995
2) had a mother residing in zip code 78211, 79237, or 78228 at the time of the birth and
3) had a birth defect indicated on a vital record (birth, death, or fetal death certificate).
Due to a change in the type of information required to be reported on birth certificates in 1989, 1990 is considered to be the first year for which reliable data on specific birth defects are available. The last year for which complete data are available is 1995.
To determine if there was a possible "excess" of birth defects in the three zip codes of concern, we compared the number of "observed" cases for each category of birth defect to the number of cases we would have "expected," based on rates for specific birth defects for the entire state. As with the cancer information, we determined the observed-to-expected ratio (O:E) and calculated the 95% confidence interval for each birth defect category. We examined the number of birthdefects for each type of vital record: birth, death, and fetal death certificates.The results are presented in the following sections, according to the type of vital record used for the analysis. Tables listing the specific number of cases and O:E ratios are found at the end of the report.
TDH compared the observed number of cases for each category of birth defect, as listed on the birth certificate check boxes, to the number that would have been expected and calculated the O:E ratio for each category of birth defects. The number of expected cases is based on the rate for specific birth defects for the entire state of Texas. The ratios were not adjusted for race or maternal age.
Tables 9-11 list information on birth defects recorded on birth certificate check boxes for each of the three zip codes of concern (78211, 78228, 78237) for the time period 1990-1995. The tables list the 22 specific birth defect categories and a nonspecific "other" category, the observed number of cases for each defect, the expected number, and the O:E ratio with the 95% confidence interval.
The only statistically significant findings from the birth certificate data are for the category "other" defects in zip codes 78211 and 78237. The category "other" is a nonspecific category, basically a "catch-all" category for birth defects that are not attributed to one of the 22 categories of specific defects. The defects listed in the "other" category may include a wide variety of defects of different structural systems, some of which may be very serious or merely cosmetic, and whose cause(s) may be very diverse. A nonspecific category such as "other" is difficult to interpret because it is not possible to tell if the elevated O:E ratios are due to a slight elevation in many different defects listed in the "other" category or if it is due to larger increases in one or two kinds of defects listed in the category.
There were no statistically significant elevations of any O:E ratios for conditions listed on fetal death certificates for any zip code. Tables 12-14 list the number of observed and expected cases for each birth defect category and the O:E ratios with 95% confidence intervals for the individual zip codes for the time period 1990-1995.
Death certificates for children less than one year old were also reviewed (Tables 15-17), and 17 specific categories of birth defects were evaluated for 1990-1995. No statistically significant elevations in the O:E ratios were seen for any of the defects in zip codes 78211 and 78228. The O:E ratios for three categories of heart and circulatory system-related defects were significantly elevated for zip code 78237. The elevated ratios were for the categories "bulbus cordis anomalies and anomalies of cardiac septal closure" (ICD-9 745), "other congenital anomalies of the heart" (ICD-9 746), and "other congenital anomalies of the circulatory system" (ICD-9 747). Several children had more than one heart or circulatory system defect listed on their death certificate (19 defects reported for 14 infants).
The review of the 1990-1995 birth certificate and fetal death certificate data for zip codes 78211, 78228, and 78237 did not indicate an excess number of birth defects for any specific category of defect examined. The O:E ratios for the nonspecific "other" category on birth certificates were elevated for zip codes 78211 and 78237, but due to the nonspecific nature of the category, do not warrant additional analysis at this time. The infant death certificate data for zip code 78237, however, indicate an excess of reported cases for three categories of heart and circulatory system-related defects for 1990-1995.
Because of the increased occurrence of heart and circulatory-related defects in zip code 78237, additional analyses were performed to further examine the elevated O:E ratios for these categories. To determine if race/ethnicity may have accounted for or contributed to the elevated number of cases reported, the O:E ratios based on infant death certificate data for zip code 78237 were statistically adjusted for race and ethnicity (Table 18). Adjustment for race/ethnicity was performed because the race/ethnicity distribution of the San Antonio population differs from the population distribution of the state of Texas, our comparison population. During 1990-1995, 96.4% of all live births in San Antonio were Hispanic, while only 39.7% of all live births in the state of Texas were of Hispanic origin. If the comparison population does not reflect the race/ethnicity distribution of the study population (the San Antonio area), then the expected number of cases used for comparison may be overestimated or underestimated.
After adjusting for race/ethnicity, the O:E ratios for each of the three birth defect categories changed only slightly. The O:E ratios for "bulbus cordis anomalies and anomalies of cardiac septal closure" (ICD-9 745) and "other congenital anomalies of the heart" (ICD-9 746) remained significantly elevated for zip code 78327. The O:E ratio for "other congenital anomalies of the circulatory system" decreased slightly, and although it remained elevated, it is no longer statistically significant.
TDH also examined the information available on the birth and death certificates for the infants reported with these defects in zip code 78237. The age range of the mothers was 16-40 years with an average age of 24 (median age = 23). Nine of the 14 children (64%) were girls. As previously noted, several children had multiple heart and circulatory system-related defects. One child had a diagnosed chromosomal defect.
TDH also calculated the O:E ratios for the three heart and circulatory system-related defects, adjusting for maternal age. Table 19 lists the observed and expected number of cases, the O:E ratio, and the 95% confidence interval for each birth defect. As would be expected from the California data, adjusting for mother's age increases the O:E ratios for each defect and all O:E ratios remained statistically significant.
The cause(s) for the apparent excess of heart and circulatory system-related defects for zip code 78237 are not immediately evident. We know that for specific heart and circulatory system defects, several risk factors (factors that may increase the risk of a mother delivering a baby with a heart or circulatory system defect) have been identified. These risk factors include maternal diabetes, drinking alcohol, taking large amounts of vitamin A, and taking certain medications such as valproic acid or amphetamines. We do not have information which would allow us to evaluate the possible effect of these risk factors on the cases of heart and circulatory system defects for zip code 78237. We are recommending, however, continued monitoring of heart and circulatory system defects in zip code 78237 using vital statistic information and data from the Texas Birth Defects Monitoring Division as it becomes available.
Information on low birth weight is obtained from birth certificates from the Texas Department of Health's Bureau of Vital Statistics. A low birth weight infant is defined as an infant who is born weighing less that 2,500 grams (5.5 pounds). For this health assessment, a case was defined as an infant weighing less than 2,500 grams (5.5 pounds) at birth who was born from 1990-1995 to a mother residing in one of the three zip code areas studied.
To determine if there were an excess number of low birth weight babies born in the three zip codes in 1990-1995, the number of low birth weight babies born in each zip code was compared to the number expected based on low birth weight rates for the entire state of Texas for the same time period. For each zip code area, Table 20 lists the number of low birth weight babies, the number expected, and the O:E ratio with 95% confidence intervals. Zip codes 78211 and 78228 did not have a significantly elevated number of low birth weight babies reported. The O:E ratio for zip code 78237 was statistically significant.
The review of the 1990-1995 low birth weight data from infant birth certificates for zip codes 78211, 78228, and 78237 indicated an excess number of low birth weight babies born in zip code area 78237. There are a number of risk factors which may increase a woman's chance of delivering a low birth weight baby. Women who smoke, drink alcohol, have poor nutritional habits, or who use illicit drugs have an increased risk for low birth weight babies. Lack of access to early prenatal care has also been associated with an increased risk of delivering a low birth weight baby. TDH did not have information available which would allow them to look at the role these risk factors may have played in the reported excess of low birth weight babies for zip code 78237.
In short, there are a number of factors that play an important role in the health of the mother and developing fetus and may affect birth weight. Some of these factors can be controlled by the mother, others cannot. However, given the community concerns and the fact that the number of low birth weight babies was elevated for zip code 78237 for 1990-1995, we recommend continued monitoring as additional data becomes available.
In order to address concerns regarding lead levels, we looked at information
provided by the Texas Department of Health's Bureau of Women and Children on
blood lead levels in children less than 5 years of age who were tested in 1993-1995
in three zip code areas: 78228, 78237, and 78211. This information is collected
only for children who were tested under the Medicaid program. Blood lead levels
are considered to be elevated if they are greater than or equal to 10 micrograms
per deciliter (>10 µg/dL). The U.S. Centers for Disease Control
and Prevention (CDC) has defined blood lead levels of >10 µg/dL
in children to be a level at which action or intervention is warranted.
Tables 21-23 detail the results of blood lead
tests in children for the three zip codes.
In 1993, 574 blood lead tests were conducted on children less than 5 years of age to determine their blood lead levels. In 1994 and 1995, 285 and 296 children were tested in zip code 78211 (Table 21). The percentage of tests with elevated blood lead levels greater than 10 µg/dL was 10% in 1993, 4% in 1994, and 8% in 1995. Less than 2% of the test results reported were greater than 20 µg/dL each year.
In 1993, 577 blood lead tests were conducted on children less than 5 years of age to determine their blood lead levels. In 1994 and 1995, 459 and 519 children were tested in zip code 78228 (Table 22). The percentage of tests with elevated blood lead levels greater 10 µg/dL was 5% in 1993, 3% in 1994, and 4% in 1995. Less than 2% of the test results reported were greater than 20 µg/dL each year.
In 1993, 635 blood lead tests were conducted on children less than 5 years of age to determine their blood lead levels. In 1994 and 1995, 503 and 530 children were tested in zip code 78237 (Table 23). The percentage of tests with elevated blood lead levels greater 10 µg/dL was 7% in 1993, 4% in 1994, and 7% in 1995. Less than 1% of the test results reported were greater than 20 µg/dL each year.
Between 1993 and 1995, cases of elevated blood lead levels were reported in 90% of the zip code areas in Bexar County. However, this information is limited in that it only includes children who were tested under the Medicaid program. This information also does not provide information on the number of children who may have been tested more than once.
Statewide in 1994 and 1995, the percentage of children less than 5 years of age who had their first blood lead screening tests and were found to have elevated blood leads (>10 µg/dL) was 6% in 1994 and 5.5% in 1995. The Centers for Disease Control, the Texas Department of Health, and many local health departments have established protocols for intervention with children with elevated blood lead levels. For children with elevated blood lead levels (>10 µg/dL), medical care providers are asked to retest the child. If a child's second test shows an elevated blood level ( >10 µg/dL, but less than 20 µg/dL), it is recommended that the medical care provider talk with the parent about possible sources of lead exposure and that the child be retested in 3-4 months. If the child's second test shows a blood lead level >20 µg/dL, follow-up and counseling should be conducted by the medical care provider and the Texas Department of Health or local health department will send a packet of information to the child's parents about lead poisoning. The packet, available in English and Spanish, explains what lead poisoning is, lists potential sources of lead in the home and environment, and recommends specific activities parents can do to limit exposure. In addition, the medical care provider may request that a public health nurse to visit the home to talk with the parents in person. If necessary, an environmental investigator may also be asked to visit the child's house to help identify specific sources of lead exposure. The investigator may also test various items such as paint, water, soil, and dishes for possible lead contamination. Children with elevated blood lead levels will be followed, including additional blood lead tests, until the blood lead level is below 10 µg/dL. The local, regional, and state health departments may all be involved in various aspects of the followup.
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