NATIONAL BLOOD LEAD POISONING CONTINUES TO DECLINE

In the February 21, 1997 issue of the Morbidity and Mortality Weekly Report, the Centers for Disease Control and Prevention (CDC) published an update of blood lead levels (BLL) in the US population. That update was based on a report from the National Health and Nutrition Examination Survey (NHANES). NHANES III Phase 2 was conducted between October 1991 and September 1994 and updated national BLL estimates. The national geometric mean (GM) BLL for persons aged 1-74 years has declined from 2.9µg/dL to 2.3 µg/dL. The prevalence of elevated blood lead levels (EBLL) >10 µg/dL decreased from 4.4% to 2.2%. The GM BLL for children ages 1-5 years of age was 2.7 µg/dL with a prevalence of EBLL of 4.4%. The highest levels were found in children ages 1-2 and persons >50 years. Among children 1-2 years of age, the national GM BLL was found to be 3.1 µg/dL with a prevalence of EBLL of 5.9%.

SURVEILLANCE OF CHILD BLOOD LEAD LEVELS, UTAH 1996

During 1996, the CBLES project received reports of blood lead levels on approximately 0.79% (1839) of children <5 years old living in Utah. About 65% of those reports were on children 1 and 2 years of age. The geometric mean blood lead level was 3.0 µg/dL, slightly higher than the national average of 2.7 µg/dL. Blood lead levels ranged from <0.1 (less than the analytical limits of detection) to 35.0 µg/dL. Eighty-nine children were reported with EBLL >10 µg/dL. Elevated blood lead levels were categorized as confirmed if the test was performed on a venous blood sample or if the child had a follow-up EBLL. Unconfirmed EBLL cases are those cases where only one blood lead test was performed for that child using a capillary blood sample. Of the 89 children, 35 were confirmed cases, 15 were found to be <10 µg/dL by a confirmation test, and 39 cases were unconfirmed. The prevalence of elevated blood lead levels was between 1.9% (confirmed) and 4.0% (confirmed and unconfirmed). That prevalence range would indicate that as many as 9,200 children living in Utah may have blood lead levels >10 µg/dL. This prevalence range is slightly lower than the national average of 4.4% for children 1-5 years of age.

CDC RELEASES DRAFT GUIDELINES FOR CHILD BLOOD LEAD TESTING

In February 1997, CDC released a draft of screening guidelines: Screening Young Children for Lead Poisoning: Guidance for State and Local Public Health Officials. That document suggests two approaches for childhood lead poisoning screening and the criteria to select the most appropriate approach for screening children. Those approaches are universal screening and targeted screening. Universal screening is the testing of all children ages 1 and 2 and all children 3-6 years old who have not been previously screened. With targeted screening, only children in certain high risk populations are tested for elevated blood lead levels. Two specific criteria are given that determine if targeted rather than universal screening is appropriate. One criterion is the percentage of housing stock built before 1950. The CDC draft guidelines recommend that targeted screening may be appropriate if the area under consideration has less than 27% of its housing stock built before 1950. Figure 1 is a map of the percentage of housing stock built before 1950 in each county in Utah (based on 1990 census data). The other selection criterion is the percentage of children with elevated blood lead levels in the state or geographic region. The CDC draft guidelines recommend that targeted screening may be appropriate in areas where a significant amount of universal screening has occurred and the prevalence of children with elevated blood lead levels is found to be <12% and the housing criterion is also met.

Figure 1. Percent of Utah Housing Stock Built before 1950 by County.

Copies of the new guidelines can be obtained by calling 1-888-232-6789, or down loaded from the Internet at http://www.cdc.gov/nceh/programs/lead /lead.htm.

Utah Administrative Code R386-703 (Injury Reporting Rule) establishes an injury surveillance and reporting system for major injuries occurring in Utah. Lead poisoning was added to the list of reportable injuries in 1990. Initially, under the rule, lead poisoning injuries were defined to include lead poisoning of all persons with whole blood lead concentration >30 µg/dL. In December 1991, the reportable level was lowered to >15 µg/dL, and effective January 1, 1997, the reportable level was lowered to >10 µg/dL.

Generally, the Bureau of Epidemiology (BOE) obtains blood lead test results from the laboratory performing the tests. However, the rule also specifies that hospitals, physicians, nurses, other health care practitioners and medical examiners are also required to report. Reports should include the injured persons name, date of birth or age if date of birth is unknown, gender, address of residence, date of sampling, date of testing, physician or clinic requesting the test and their phone number. Each case of injury can be reported to the BOE or to the local health department responsible for the geographic area where the injury occurred. The local health officer can then forward all reports of blood lead levels to the BOE.

SURVEILLANCE OF ADULT BLOOD LEAD LEVELS, UTAH 1996

The primary source for adult exposure to lead occurs in the work place. Since 1990, the Bureau of Epidemiology has maintained the Utah Blood Lead Registry (UBLR). In 1992, the bureau established the Adult Blood Lead Epidemiology and Surveillance (ABLES) Project, to study the epidemiology of occupational lead poisoning in Utah adults, and to develop and disseminate information about adult blood lead poisoning to employees and employers working in the lead industries.

Elevated blood lead levels >15 µg/dL on 129 Utah adults (18 years of age or older) were reported to the UBLR during 1996. Ninety-seven of those adults were reported for the first time. The range of EBLL was 15.0 to 54.0 µg/dL with a GM of 23.3 µg/dL. Those values are lower than in 1995 (range of 15.0 to 65.8 µg/dL, GM of 24.3 µg/dL). The range and GM BLL of reports received in the registry for each year that the registry has been in existence are presented in Figure 2. The prevalence of EBLL in adults in Utah has also decreased since 1995. Figure 3. shows a history of prevalence rates since 1992.

Figure 2. Highest Blood Lead Level Reported and Geometric Mean of All Elevated Blood Lead Levels in Utah Adults (ages 18 and older) Reported to the Utah Blood Lead Registry by Year.

Figure 3. Prevalence of Elevated Blood Lead Levels Among Utah Adults (ages 18 and older) Employed in Non-Agricultural Jobs per 100,000 Population

Follow-up phone surveys were conducted on 28 individuals who were new 1996 cases with EBLL >25 µg/dL. Those surveys asked about significant personal risk factors. The most significant personal risk factor identified was the use of house and auto paint and participating in target practice. Those risk factors are consistent with what has been found in previous years. The potential of secondary exposure to occupational lead by children is also of interest. In 1996, 29% of the cases surveyed had children in the high-risk age group (0-6 years old) living at home. The individuals surveyed were also asked questions about occupational protective measures and occupational risk behavior they practiced. Case reported employer control measures include providing showers at the work site and lead risk training. The number of cases responding affirmatively to questions about control measures were significantly lower in 1996 than in 1995 (41% in 1996 versus 64% in 1995 reported showers available at the work site and 43% in 1996 versus 73% in 1995 reported that they had received lead risk training). Occupational risk questions on the survey included questions about protective measures such as changing clothing and taking a shower before leaving the worksite and negative risks such as use of tobacco and eating snacks in the work area. Figure 4. presents a comparison of the percents of cases responding affirmatively to questions about protective measures and occupational risks for 1994 through 1996.

Figure 4. Trend of Affirmative Responses to Occupational Risk Factors Among Utah Adults (18 and older) Employed in Non-Agricultural Jobs With Elevated Blood Lead Levels (> 40 µg/dL) for 1994-1996.

                                              Showers Available refers to the availability of showers at the work site.
                                              Takes Shower refers to those employees who have showers at the work site and take showers prior to going home.
                                              Training Received refers to training regarding the health effects of lead, protective clothing, or the lead standard.
                                              Changes Clothing refers to the employee changing into clean clothes before leaving the work site.
                                              Uses Tobacco refers to those employees who smoke or use smokeless tobacco in their work area.
                                              Snack refers to those employees who eat or have snacks including chewing gum at their work area.

Ten of 24 cases (42%) surveyed (with blood lead levels >25 µg/dL) reported experiencing one or more symptoms of EBLL. Five cases had blood lead levels >40 µg/dL. Of those cases, only 1 (20%) reported experiencing one or more symptoms. The only case to report experiencing all symptoms queried about in the survey was the case of an accidental gun shot wound (blood lead level 30.4 µg/dL). The most commonly identified symptoms were muscle pain and headaches.

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