EMA Case Study Series

Transcription

1 EMA Case Study Series A National Baseline Survey On Blood Lead Levels [BLLs] Establishing a geometric mean BLL for Trinidad & Tobago for primary school children ages 5-7 1

2 In keeping with the global trend to eliminate lead in gasoline the Government of the Republic of Trinidad and Tobago [GORTT] took a decision effective April 1 st 2004 to stop the sale of leaded fuel on the local market. In light of this initiative and the fact that there had never been any large scale Blood Lead Level [BLL] survey for Trinidad and Tobago, the Environmental Management Authority [EMA] in collaboration with the Ministry of Health [MOH] embarked on a study to carry out a national baseline survey on BLLs by collecting and analyzing blood from a representative sample of primary schoolchildren between the ages of 5 to 7 years old. Why the concern about lead? Lead is dangerous because it is widely used, it never breaks down into a harmless substance, and it lasts forever in the environment. It is especially dangerous to children, and reducing their exposure is vital to their health. A weighty yet soft material, it has numerous uses in modern life, from coins, fine crystal, ceramics, printer's ink, solder, water pipes, shields against radioactivity, ammunition, and even fishing gear. At one time lead was commonly used in additives for gasoline and paint. This is still a concern but less frequently so. Some household items, such as older, vinyl miniblinds, even contain minor amounts of lead. History in the making BLL testing was conducted during the period April 19 to June , which coincided with the final term of the 2003/04 school academic year. Prior to the survey, a package was sent to each participating school, which included the following: A letter to the Principal explaining the purpose of the study and seeking his or her consent to have the school participate in the study; Letters to parents/guardians of the children of the selected age group informing them about the survey; A consent form to be completed by the parents/guardians; and A personal risk assessment survey questionnaire along with instructions for the parents/guardians. Once consent was granted, the parent/guardian of the selected child was required to complete the personal questionnaire, which included six risk assessment questions as identified by the Centers for Disease Control [CDC], A child was considered to be high risk for lead exposure if a parent/guardian answered, yes to one or more of the risk assessment questions. In schools where the number of volunteers exceeded 50, students were randomly selected prior to BLL testing. 2

3 The 6 risk assessment questions as identified by CDC, Does your child have a brother/sister or playmate that has or did have lead poisoning? 2. Did your child already have his or her blood lead tested? 3. Does your child live with an adult whose job or hobby involves lead? Examples include welding, soldering, pottery, stained glass, making bullets or fishing weights or recycling car batteries. 4. At any time have you lived near a factory where lead is used, for example a lead smelter or a paint factory? 5. Do you give your child any home or folk remedies that contain lead? Examples include kajal, teething powder, calcium supplements from bone meal. 6. Does your child eat soil, paint chips or other non-food substances? In all, 1761 students from 42 primary schools in Trinidad and 19 primary schools in Tobago were screened for BLLs with a socio-demographic makeup of 53% female, 47% male, 38% African and Indian, and 23% of mixed race. Only 82% of the respondents completed the question on monthly economic income, which corresponded to 35% low, 36% middle and 11% upper. Participating s Arima Hindu Primary Arouca Anglican Primary Belle Gardens Anglican Primary Bethesda Government Primary Bien Venue Presbyterian Primary Bon Accord Government Primary Brazil Roman Catholic Primary Caroni Hindu Primary Castara Government Primary Chaguanas Roman Catholic Primary Charlotteville Seventh Day Adventist Primary Clarke Road Hindu Primary Cumana Roman Catholic Primary Cunupia Government Primary Curepe Presbyterian Primary Diamond Vale Government Primary El Dorado North Hindu Primary Enterprise Government Primary Erin Roman Catholic Primary Freeport Presbyterian Primary Fyzabad Presbyterian Primary Goodwood Methodist Primary Grant Memorial Presbyterian Primary Guayaguayare Roman Catholic Primary La Brea Roman Catholic Primary Lambeau Anglican Primary Las Cuevas Government Primary Las Lomas Roman Catholic Primary Lower Cumuto Government Primary Manzanilla Government Primary 3

4 Participating s [Cont d] Matelot Roman Catholic Primary Matura Government Primary Mayaro Government Primary Montrose Vedic APS Primary Moriah Government Primary Moulton Hall Methodist Primary Mount St. George Primary Munroe Road Hindu Primary Palatuvier Anglican Primary Patience Hill Government Primary Penal Presbyterian Primary Princes Town ASJA Primary Rochard Douglas Presbyterian Primary Roxborough Anglican Primary San Fernando TML Primary San Juan Presbyterian Primary San Rafael Roman Catholic Primary Scarborough Methodist Primary Scarborough Roman Catholic Primary Scarborough Seventh Day Adventist Primary Signal Hill Government Primary Speyside Anglican Primary St. Andrews Anglican Primary St. Christopher s Anglican Primary St. Joseph TML Primary St. Patrick Anglican Primary St. Theresa Roman Catholic Primary Talparo Roman Catholic Primary Tunapuna Presbyterian Primary Valencia Government Roman Catholic Primary Woodbrook Presbyterian Primary 4

5 The actual analysis Capillary blood samples were taken on site from the subjects by qualified nurses and the samples were analyzed by technicians certified in using the LeadCare Blood Lead Testing System [LCBLTS]. The LCBLTS portable technology quantifies lead levels in minutes on fresh whole blood samples via fingerstick using reagents and an electrochemical sensor based on the principle of anodic stripping voltammetry (ESA, 1996). Blood samples from participants were collected in a clean, air-conditioned room at each school (in cases where this was not available, a mobile laboratory equipped with clean room conditions was used) operating in a temperature range o C and relative humidity of 70-85% during testing. Before collecting blood samples, the student s hands were thoroughly washed with liquid soap, under adult supervision. Great care was taken to ensure no physical contact with the surroundings once the hands were washed. The collected sample (approximately 50µL) was transferred into a treatment reagent, mixed and then placed onto the sensor strip for lead analysis. The instruments were calibrated daily in the field and quality control materials (low and high level reference standards) were analyzed before each analytical run. In cases where BLL was 10µg/dL, the child was immediately retested, with the nurse paying particular attention to all the preparatory steps involved. Results were accepted when a similar result was obtained after two consecutive tests. To validate the LCBLTS as well as confirm elevated cases, subjects with BLLs 5µg/dL were identified for venipuncture (venous blood sample) during the course of the study. The 5µg/dL criterion was used because not enough cases were obtained at BLL 10µg/dL. A lead free alcohol swab was used to wipe the finger, before blood was drawn from the finger. After sticking, the first two drops of blood were discarded and the next two drops were collected, using a blood capillary tube. 5

6 Test results Figure 4a. High Level Control Chart BLL (ug/dl) Control Std. lower limit upper limit Daily Observations Figure 4b. Low Level Control Chart BLL (ug/dl) Control Std. lower limit upper limit Daily Observations BLLs for the 5-7 year olds ranged from micrograms/deciliter [μg/dl] Among the children tested, BLLs were generally low with 94% of the sample population 6µg/dL. The overall geometric mean BLLs for the 5-7 age group was 2.8µg/dL and compared favorably with results from the more developed countries of the world. These results suggested that lead may not be a major public health concern except in localized populations in Trinidad and Tobago. While other countries have demonstrated (through monitoring programmes) that lead reduction measures - especially the removal of lead in gasoline - have resulted in a decline in BLLs over the years (Langlois, et al., 1996; Stromberg et 6

7 al., 1995; Schumacher, et al., 1996; Delves, et al., 1996), very little data is available locally to substantiate the results from this study. A 1985 study done by the Ministry of Health [MOH] on 166 children aged 5-11 years from urban and rural communities in Trinidad reported a higher range (8-78µg/dL) than this study (GORTT, 1993) A study done on 280 primary school children aged 9-10 years reported a mean BLL 8.0 µg/dl and a range of 2-26µg/dL (UWI, Department of Child Health unpublished). The amount of lead found in a child s blood is called a blood lead level. Blood lead tests tell how many micrograms (millionth of a gram) of lead are in each deciliter (tenth of a liter) of a child s blood (μg/dl). While these two studies do provide some empirical data to show a reduction in BLLs in children, over the years there has also been some anecdotal information that may support this trend and the results of this study as follows: Lead in gasoline has been reduced over the years and stood at 0.1g/L prior to phase out in April 2004 (personal communication PETROTRIN, 2004); Consumption of leaded gasoline was reduced in 1997 with the introduction of unleaded fuel; Decommissioning of the secondary lead smelter in early 1990s and subsequent recycling of expired/used/defective lead acid batteries external to Trinidad and Tobago (personal communication Automotive Company Limited, 2004); Removal of lead in residential paints 2-5 years ago (personal communication various paint companies, 2004); Cessation in the manufacture of lead-soldered food cans 13 years ago (GORTT, 1992) and The use of unleaded coated steel pipes and polyvinyl chloride (PVC) pipes in the water supply and distribution network has been instituted for over 25 years (personal communication Water and Sewerage Authority, 2004). Are there any differences in BLL levels between Trinidad and Tobago? An analysis of variance was conducted on the BLLs data to look for differences between the island of Trinidad and the island of Tobago as well as within the two islands. Slightly higher BLL (p<0.05) was found in 6 and 7 year-olds in Trinidad (mean 3.3µg/dL and 3.2µg/dL, respectively) when compared to Tobago (mean 2.8µg/dL and 2.5µg/dL, respectively) but no difference was seen for the 5 year-olds. Male and female students in Trinidad (mean 3.5µg/dL and 3.1µg/dL, respectively) had higher BLLs than their Tobago counterparts (mean 2.9µg/dL and 2.6µg/dL, respectively). 7

8 Africans in Trinidad had higher BLLs (mean 3.6µg/dL) than in Tobago (mean 2.8µg/dL) but no difference was observed for students of Indian decent and mixed race. Higher BLLs were observed for the upper and lower groups in Trinidad (mean 3.3µg/dL and 3.4µg/dL, respectively) than for those in Tobago (mean 2.4 µg/dl and 2.8µg/dL, respectively), but no difference for the middle class. Although the differences in certain demographic variables were minor between the islands, the consistently higher BLLs for Trinidad might be due to the higher level of economic and urban development in Trinidad compared to Tobago. An attempt was made to calculate a motorization index (i.e. number of vehicles per 1,000 persons) for Trinidad and Tobago; unfortunately statistics on vehicle registrations were not disaggregated at the time. It has been reported that for a given concentration of lead in gasoline, higher BLLs are to be found in regions that are more populated and use more gasoline (Brody, et al., 1994; Valerie, et al., 1999). Within Trinidad, males had slightly higher BLLs (mean 3.5µg/dL) than females (mean 3.1µg/dL) but no differences were observed between the sexes in Tobago. Differences within the 5-7 age group were only observed in Tobago where there were slightly higher BLLs for the 5 year olds (mean 3.0µg/dL) compared with the 7 year olds (mean 2.5µg/dL) as well as for the 6 year olds (mean 2.8µg/dL) compared with 7 year olds (mean 2.5µg/dL). No statistical differences were observed between ethnicities and economic groups except in Trinidad where higher BLLs were seen in Africans (mean 3.6µg/dL) when compared to Indians (mean 3.1µg/dL) and higher BLLs for the low-income class (mean 3.5µg/dL) compared to the middle-income class (mean 3.1µg/dL). Higher BLLs in males than females as well as higher BLLs in the lower income class have been reported in the literature (Mahaffey et al., 1982; Brody et al., 1994; Rubin et al. 2002; Pirkle, et al. 1994; CDC, 1997a; Lalor, et al. 2001). LEAD FACTS: FACT: Lead exposure can harm young children and babies even before they are born. FACT: Even children who seem healthy can have high levels of lead in their bodies. FACT: You can get lead in your body by breathing or swallowing lead dust, or by eating soil or paint chips containing lead. 8

9 Applying Centers of Disease Control [CDC] classification Applying CDC classification to the diagnostic BLLs results (n=111), 74% of the cases fell within the normal range (<10µg/dL) that would require no further action. Lead and its effect on our lives People of all ages are susceptible to lead poisoning. However, children are at greater risk for lead poisoning than adults, and are more susceptible to its harmful effects. Young children are at greatest risk for lead poisoning because they absorb lead more easily and have a lot of hand-to-mouth contact. effects of lead poisoning usually cannot be reversed. Final words The results from this study form an important reference point for future studies and can be used to guide and inform a realistic national standard for blood lead levels. Future surveillance studies would provide useful data to validate the findings from this study, as well as assess the impact of lead removal in gasoline and other management strategies aimed at eliminating lead exposure. For more information on Lead hazards, abatement or permanent hazard elimination please contact the EMA Growth patterns, development, and increased metabolism make children more sensitive to the harmful effects of lead. Lead can have wide-ranging effects in humans, depending upon the level. Even very low lead levels can affect children's developing nervous systems, causing delayed development, lowered IQ scores, reading and learning problems, hyperactivity, and discipline problems. Larger doses of lead can affect adults as well as children and can cause problems such as high blood pressure, anemia, kidney trouble, and reproductive disorders. During substantial lead removal from the home, children and pregnant or nursing women should live elsewhere until the site has been declared safe from lead residue. Lead tends to accumulate in the body, and the 9

10 EMA Green Tips If you suspect that your house has lead hazards, you can take some immediate steps to reduce your family's risk: If you rent, notify your landlord of peeling or chipping paint. Clean up paint chips immediately. Clean floors, window frames, window sills, and other surfaces weekly. Use a mop, sponge, or paper towel with warm water and a general all-purpose cleaner or a cleaner made specifically for lead. REMEMBER: NEVER MIX AMMONIA AND BLEACH PRODUCTS TOGETHER SINCE THEY CAN FORM A DANGEROUS GAS. Thoroughly rinse sponges and mop heads after cleaning dirty or dusty areas. Wash children's hands often, especially before they eat and before nap time and bed time. Keep play areas clean. Wash bottles, pacifiers, toys, and stuffed animals regularly. Keep children from chewing window sills or other painted surfaces. Clean or remove shoes before entering your home to avoid tracking in lead from soil. Make sure children eat nutritious, low-fat meals high in iron and calcium, such as spinach and dairy products. Children with good diets absorb less lead. Environmental Management Agency [EMA] 8 Elizabeth Street St. Clair P.O. Box 5071 Port of Spain, Trinidad W.I. Telephone: Fax: [email protected] 10