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Blood Lead Levels and Risk Factors in Pregnant Women from Durango, Mexico a

a

Osmel La-Llave-León PhD , Sergio Estrada-Martínez MSc , José Manuel Salas-Pacheco PhD a

a

Gonzalo García Vargas PhD a

b

b

, Rocío Peña-Elósegui , Jaime Duarte-Sustaita , Jorge-Luís Candelas Rangel MPH & b

Institute of Scientific Research , , University of Juárez at Durango,Gómez Palacio , México

b

Faculty of Medicine , , University of Juárez at Durango,Gómez Palacio , Durango , México Published online: 17 Jun 2011.

To cite this article: Osmel La-Llave-León PhD , Sergio Estrada-Martínez MSc , José Manuel Salas-Pacheco PhD , Rocío PeñaElósegui , Jaime Duarte-Sustaita , Jorge-Luís Candelas Rangel MPH & Gonzalo García Vargas PhD (2011) Blood Lead Levels and Risk Factors in Pregnant Women from Durango, Mexico, Archives of Environmental & Occupational Health, 66:2, 107-113, DOI: 10.1080/19338244.2010.511311 To link to this article: http://dx.doi.org/10.1080/19338244.2010.511311

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Blood Lead Levels and Risk Factors in Pregnant Women from Durango, Mexico ´ PhD; Sergio Estrada-Mart´ınez, MSc; Jos´e Manuel Osmel La-Llave-Leon, ´ Salas-Pacheco, PhD; Roc´ıo Pe˜na-Elosegui; Jaime Duarte-Sustaita; Jorge-Lu´ıs Candelas Rangel, MPH; Gonzalo Garc´ıa Vargas, PhD

ABSTRACT. In this cross-sectional study the authors determined blood lead levels (BLLs) and some risk factors for lead exposure in pregnant women. Two hundred ninety-nine pregnant women receiving medical attention by the Secretary of Health, State of Durango, Mexico, participated in this study between 2007 and 2008. BLLs were evaluated with graphite furnace atomic absorption spectrometry. The authors used Student t test, 1-way analysis of variance (ANOVA), and linear regression as statistical treatments. BLLs ranged from 0.36 to 23.6 µg/dL (mean = 2.79 µg/dL, standard deviation = 2.14). Multivariate analysis showed that the main predictors of BLLs were working in a place where lead is used, using lead glazed pottery, and eating soil. KEYWORDS: blood lead, lead glazed pottery, pregnant women, risk factor

L

ead (Pb) is a nonessential metal for human beings, it does not have useful function in the human body1 and the use of this metal causes damage to human beings and environmental contamination.2 Blood lead levels (BLLs) are influenced by recent exposure, excretion, and balance with other tissues.3 Several studies in women have suggested that some conditions, such as gestation, lactation, and osteoporosis, are associated with mobilization of bone lead toward the blood stream.4 This raises lead levels and results in lead transfer across the placenta to the fetus.5,6 Exposure to lead in the womb is an important condition because in this stage the central nervous system is sensitive to the toxins. Such exposure has been associated to lower weight at birth, growth delay,7 and deficits in cognitive function.8 During pregnancy, the metal can enter the blood stream and have deleterious effects on the fetus.9,10 The endogenous reserves of lead can affect the viability of the fetus, pro-

voking miscarriages, lower weight at birth, premature births, congenital malformations, deficits of attention, and adverse effects on neurological development, even when the patient is not exposed to the toxin.9–13 Severely elevated BLLs are associated with poor health outcomes.14 Prenatal lead exposure in the first trimester of pregnancy has been associated to low mental development index scores in offspring.15 Also, Rabinowitz et al3 found that during the early embryonic and fetal stages, lead can pass through the placenta to affect the central nervous system. Lead exposure around 28 weeks of gestation is considered a critical period for the subsequent cognitive development of the child.4,16,17 The US Centers for Disease Control and Prevention (CDC) define 10 µg/dL as blood lead level of concern in children and pregnant women. Nevertheless, some authors have reported damages to health at lower levels of lead in blood.10,11,13,18,19 Recent studies mention the presence of neurological and

˜ Osmel La-Llave-Le´on, Sergio Estrada-Mart´ınez, Jos´e-Manuel Salas-Pacheco, and Roc´ıo Pena-El´ osegui are with the Institute of Scientific Research, and Jaime Duarte-Sustaita, Jorge-Lu´ıs Candelas Rangel, and Gonzalo Garc´ıa Vargas are with the Faculty of Medicine, University of Ju´arez at Durango, G´omez Palacio, Durango, M´exico. 2011, Vol. 66, No. 2

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behavioral disabilities in children who have levels of lead in blood below 10 µg/dL.8,13 Also miscarriages, low weight at birth, decrease of the cephalic perimeter, and inhibition of cognitive development have been observed.10,11 Women with BLLs between 5 and 10 µg/dL have 2 to 3 times higher probability of having a miscarriage than those with concentrations of lead in blood lower than 5 µg/dL.11 Low levels of lead exposure may be a risk factor for hypertension during pregnancy.18 Occupational environment is recognized as one of the most important sources of lead exposure,16,20,21 but at present there are some well-established causes of lead poisoning in household that affect principally children13,22–26 and pregnant women.9–11,18 Sources of lead that have been shown to contribute to elevate blood lead concentrations include using of ceramic ware for cooking and storing foods,27–29 living next to smelter30 or battery factory,11,18,27 and consumption of nonfood products, such as plastered painting of the walls or soil.22–26 The use of lead-glazed ceramics has been identified as a source of cumulative exposure to lead in the early postpartum period31; (31); and Rothenberg has shown that a history of pica has been significantly associated with higher BLLs, whereas use of folk remedies has been associated marginally with increased lead levels in blood.32 In Mexico, the Secretary of Health in every state is divided in sanitary jurisdictions, which are organs of technical and administrative linkage with the responsibility of administering services of health that abide open population on the subject of medical attention, public health, and social assistance. We conducted this study to determine the levels of lead in blood and to identify environmental and occupational risk factors for elevated BLLs in pregnant women who received medical attention in jurisdiction number 1 and jurisdiction number 2 of the Secretary of Health, Durango. METHODS Study Sample This cross-sectional study was carried out between June 2007 and May 2008 in 12 municipalities of the State of Durango, Mexico. The study populations consisted of pregnant women who received medical attention in the sanitary jurisdiction numbers 1 and 2 by the Secretary of Health. Two hundred ninetyx-nine pregnant women were selected using a randomized stratified sampling procedure. The sample included participants from 6 municipalities in sanitary jurisdiction number 1 and 6 municipalities in sanitary jurisdiction number 2. The municipalities of jurisdiction 1 included Durango, Pueblo Nuevo, Guadalupe Victoria, El Mezquital, San Dimas, and Panuco de Coronado; and the municipalities of jurisdiction number 2 included Gomez Palacio, Lerdo, Cuencam´e, Mapim´ı, Tlahualilo, and Penon Blanco. Participants received a detailed explanation of the aims of the investigation and of the procedures to be used. They gave informed written consent before being enrolled. We 108

provided guidelines for reduction of lead exposure. Women who accepted to participate in the research answered a set of questions in a face-to-face interview. The questionnaire included questions aimed at collecting sociodemographic data and identifying reproductive variables and risk factors for occupational and nonoccupational lead exposure. The research protocol was reviewed and approved by the Ethical Committee, Durango General Hospital. This research was conducted in accordance with the Helsinki Declaration.33

Questionnaire In order to identify sociodemographic characteristics of the women, questions included municipality, age, education, marital status, number of children, pregnancies, households, occupation, smoking status, and income. We also explored the frequency of using of lead glazed pottery for cooking or storing foods or drinks, and consumption of canned food, chili-based candies, and lead-based remedies. We also collected information on some variables that have been associated to high levels of lead in blood by some researchers, such as working in a place where lead is used, living with someone who uses lead in their job, washing the work clothes together with other clothes, eating soil or other nonfood products, living next to mining zones, or near industry or laboratory where lead is used. We also evaluated other factors, such as living next to establishments that are possible sources of contamination, such as battery manufacturing or recycling plants, radiator repair shops, plumbing, junkyards, and workshops for car painting and repair. To determine whether interviewed pregnant women and their relatives have realized that they were exposed to lead, we compared the types of jobs they have had with a list that includes several jobs where lead exposure is present, according to published reports. It was considered that a person lived next to some source of exposure when the distance between her house and the establishment was up to 5 blocks (approximately 500 m).

Measurement of Lead Levels An intravenous blood sample was collected from each woman in a lead-free tube containing ethylenediaminetetraacetic acid (EDTA). Samples were analyzed with a graphite furnace atomic absorption spectrophotometer (Perkin-Elmer Analyst 800) at the laboratory of environmental toxicology, School of Medicine, University of Juarez, at Durango, Gomez Palacio. This laboratory participates in the Wisconsin State Laboratory Program of Hygiene proficiency testing (WSLHPT). As a standard reference, we use lead in bovine blood at the National Institute of Standards and Technology (NIST). Archives of Environmental & Occupational Health

of variance (ANOVA) to determine the relationship between BLLs and categorical variables. Multiple linear regression was applied to identify the relationship between blood lead concentrations and those variables that were significantly associated (p < .25) in bivariate analyses. The regression model was adjusted by age and income per capita. All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS, Chicago, IL) software for Windows, version 11.0. A p value lower.05 was considered statistically significant.

Table 1.—-Demographic Characteristics and Blood Lead Levels of Studied Pregnant Women (N = 299)

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Variables

%

Age (years) Gestational age (weeks) No. of children No. of pregnancies Income per capita (USD per month) Marital status Married Single Cohabitating Divorced Achievement of remunerated job Yes No School level Primary or no education Junior high school High school or college University Blood lead levels (µg/dL) Geometric mean ≥10 µg/dL Between 5 and 10 µg/dL

Mean

SD

24.3 24 1 2.0 146

6.7 8.7 1 2 142

50.8 19.4 29.1 0.7

RESULTS Table 1 summarizes the main demographic characteristics and associated blood lead concentrations of the participants enrolled in the study. The mean ± standard deviation (M ± SD) BLL was 2.79 ± 2.14 µg/dL. Only 3 women (1%) had BLLs above the US Center for Disease Control and Prevention (CDC) advisory level of concern of 10 µg/dL, but 23 women (7.8%) had concentrations of lead in blood between 5 and 10 µg/dL. The lower level of lead in blood was 0.26 µg/dL and the higher one was 23.6 µg/dL. This highest value was found in a woman who was employed in a chilibased candy factory. At the time of the survey, she lived next to a painting store and to a workshop for repairing radiators. Her husband worked at a workshop for repairing auto parts. Some risk factors for the 3 subjects with levels of lead above 10 µg/dL, and also for the 23 individuals with levels between 5 and 10 µg/dL, are presented in Table 2 In the first group, 100% lived with someone who worked with lead, 66.7% washed the work clothes together with other clothes, and also 66.7% lived near rubbish dump. In the second group, 34.8% lived with at least 1 occupational exposed worker,

23.4 76.6 21.7 56.2 15.4 6.7 2.79 2.38

2.14

1.0 7.8

Statistical Analysis The distribution of blood lead levels was skewed, so the data were transformed to the natural logarithm to normalize the distribution and reduce the influence of outliers when applying parametric tests. Fisher exact test was applied to examine the significance of the association between some risk factors and levels of lead above 10 and between 5 and 10 µg/dL. We use independent-sample t tests and 1-way analysis

Table 2.—-Risk Factors for Women With Blood Lead Levels Between 5 and 10 and Above 10 µg/dL Blood lead levels, µg/dL Above 10 (n = 3)

5 to 10 (n = 23)

Risk factor

n

%

n

%

p∗

Working in a place where lead is used Living with someone who works with lead Washing the work clothes together with other clothes Eating soil Living near mining zone Living near lead industry or laboratory Living near battery workshop Living near ceramic workshop Living near gas station Living near straightening and painting workshop Living near rubbish dump Living near junkyard

1 3 2 1 0 0 1 0 0 1 2 1

33.3 100 66.7 33.3 0 0 33.3 0 0 33.3 66.7 33.3

6 8 13 1 3 4 0 0 2 2 3 1

23.1 34.8 56.5 4.3 13.0 17.4 0 0 8.7 8.7 13.0 4.3

1.00 .063 1.00 .222 1.00 1.00 .115 — 1.00 .319 .085 .222

∗ Fisher

exact test.

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Table 3.—-Distribution of Blood Lead Levels (µg/dL), by Several Risk Factors, Durango, 2007—2008

Working in a place where lead is used Yes No Living with someone who works with lead Yes No Washing the work clothes Together with other clothes Alone Eating soil Yes No Living near mining zone Yes No Living near lead industry or laboratory Yes No Living near battery workshop Yes No Living near ceramic workshop Yes No Living near gas station Yes No Living near straightening and painting workshop Yes No Living near rubbish dump Yes No Living near junkyard Yes No ∗p

M

SD

26 273

4.09 2.67

4.44 1.74

117 182

3.10 2.59

1.38 2.93

135 164

3.04 2.59

2.72 1.48

21 278

3.79 2.71

3.80 1.95

29 70

3.35 2.43

1.81 2.17

34 265

3.29 2.73

1.90 2.16

50 249

2.79 2.79

3.10 1.90

5 294

2.87 2.79

1.66 2.15

59 240

2.44 2.87

1.03 2.33

52 247

2.85 2.78

3.10 1.88

42 257

3.20 2.72

3.11 1.94

34 265

3.01 2.76

3.90 1.81

p∗ .035

.149

.065

.038

.018

.032

.897

.879

.276

.874

.325

.551

value from Student t test, using log-transformed blood lead as dependent variable.

56.5% did not separate the work clothes for washing them, and 13% lived near rubbish dump. Fisher exact test did not show significant differences for analyzed variables. We analyzed the averages of blood lead levels by municipality. The highest observed values were in Cuencame (4.28 µg/dL), San Dimas (3.66 µg/dL), and Pueblo Nuevo (3.21 µg/dL). The lowest concentrations of lead were observed in Pe˜non Blanco (2.24 µg/dL), Tlahualilo (2.41 µg/dL), Mapimi (2.41 µg/dL), and Durango (2.48 µg/dL). A comparison of municipalities using ln BBL, Tukey test showed that pregnant women living in Cuencame have significantly higher blood lead levels than pregnant women living in Tlahualilo (p = .042) and in Durango (p = .002). In this study we considered 2 risk factors related to occupation: working in a place where lead is used, and living with someone who uses lead in their job (Table 3) BLLs 110

n

were higher in women who have worked in those places where lead is present. In this comparison, the Student t test showed a significant difference (p = .035). With respect to workplace-related occupations, BLLs were higher in women who live with a household member who uses lead in his job, but these differences were not statistically significant (p = .149). Furthermore, mean BLLs in pregnant women are higher, when the household member who has used lead in his job is the husband (3.40 µg/dL), or when she cohabitates with both the husband and a brother (6.08 µg/dL). The comparison was conducted with ANOVA using log-transformed BLL and the result of the analysis was statistically significant (F = 2.025; p = .016). Table 3 also shows the distribution of BLLs according to several risk factors such as living near lead sources of exposition and some habits in the domestic environment. Archives of Environmental & Occupational Health

Table 4.—-Distribution of Blood Lead Levels (µg/dL), According To Some Domestic Habits of the Pregnant Women, Durango, 2007—2008 Never M∗

Variable

Seldom n∗∗

M∗

Use of lead glazed pottery 2.73 209 2.35 Consumption of canned food 2.12 (26) 2.79 (221) Consumption of chili-based candies 2.81 (25) 2.89 (132) Consumption of lead-based remedies 2.85 (226) 3.24 (25) ∗ Mean

Frequently

Usually

M∗

n∗∗

M∗

n∗∗

M∗

36

2.29 3.65 (23) 2.32 (26) 2.63 (5)

12

3.14 2.76 (21) 2.71 (60) 1.87 (2)

11

3.79 2.79 (8) 2.86 (59) 2.26 (41)

n∗∗ p∗∗∗ 31

.004 .019 .756 .140

of BLL, µg/dL.

∗∗ Number of pregnant women. ∗∗∗ p value from ANOVA, using

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Sometimes n∗∗

log-transformed blood lead as dependent variable.

According to the Student t test, 3 variables showed significant differences: eating soil (p = .038), living near mining zone (p = .018), and living near a lead industry or laboratory (p = .032). There were other variables that recount the frequency of some domestic habits. In this case the responses were measured by the following values: never, seldom, sometimes, frequently, and usually. The averages of lead in blood presented significant differences for the use of lead-glazed pottery and for the consumption of canned food (Table 4) On having applied Tukey test, we observed that women who use ceramic glazes have BLLs higher than those who affirmed they never use them (p = .020) and also than those who do it seldom (p = .002). With regard to the consumption of canned food, significant differences were detected between the group that seldom consumes them and those who expressed they never consume these products (p = .008). On the other hand, women who consume canned food frequently presented higher level of lead in blood than those who answered they never do it, but these differences were not statistically significant (p = .053). When we analyzed consumption of chili-based candies and consumption of leadbased remedies, no statistically significant association was found.

We used linear regression model to assess the relationship between BLLs and those variables that were significantly associated (p < .25) in bivariate analyses (Table 5) Working in a place where lead is used (p < .003), the use of lead glazed pottery for eating or storing foods and drinks (p < .005), and eating soil (p < .019) are powerful predictors of high blood lead concentrations. The model represents 12% of the predictive capability: 88% remains for other predictors and the influence of randomness. COMMENT This study represents the first attempt to examine whether pregnant women in Durango are being exposed to lead and to analyze those variables that may be considered risk factors for lead poisoning in this population. We found 3 pregnant women (1%) with blood lead concentrations >10 µg/dL, and 23 (8.7%) with BLL above 5 µg/dL. Some researchers have found health injuries in women with levels of lead in blood between 5 and 10 µg/dL.8,10,11,13,18,19 The average of the BLL in the studied population (2.79 µg/dL) was lower than the level of concern threshold (10 µg/dL) but higher than levels in blood observed in pregnant women of Zacatecas, Mexico,34 and Istanbul, Turkey.35 Lead in blood found here also

Table 5.—-Regression Analysis for Predictors of Blood Lead (N = 299) Variable Working in a place where lead is used Washing the work clothes together with other clothes Use of lead glazed pottery Consumption of chili-based candies Consumption of canned food Living near mining zone Eating soil Living with someone who works with lead

Coefficient β

95% CI

p∗

0.317 0.116 0.06 .0002 0.048 0.163 0.288 0.056

0.106–0.527 −0.006–0.238 0.020–0.111 −0.045–0.05 −0.048–0.05 −0.099–0.424 0.049–0.527 −0.07–0.181

.003 .063 .005 .909 .228 .221 .019 .383

Note. R2 = .121. ∗ Adjusted for age and income.

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overcomes the levels reported in reproductive age women of New York.36 In Mexico, the largest social security institutions that provide care are the Institute of Security and Social Services for State Workers (ISSSTE) and Mexican Institute of Social Security (IMSS). So, the health care institution with the smallest workforce is the Secretary of Health. Therefore the possibility of finding occupationally exposed people would be reduced. In spite of this, we found enough exposed working women and we observed that lead in the working place is a significant determinant of blood lead levels. This result suggests, in accordance with some researchers,9,20,21,25,37,38 that occupational exposure continues to be an important risk factor for BLLs. There was no statistical association between BLLs and living with any household who has occupational exposure to lead. Nevertheless, when comparing the households, it is interesting to notice that BLLs in pregnant women were significantly higher when the relative with occupational exposure to lead was the husband, the son, or when the exposure was simultaneously to the husband and the brother of the pregnant woman. This indicates the need to study occupational exposure of the households in depth. Family members of workers exposed to lead at their workplace are considered an additional risk of elevated blood lead concentrations.39 The municipalities with higher averages of blood lead are Cuencam´e, San Dimas, and Pueblo Nuevo. In the first two, there are smelters that constitute sources of lead contamination; so this study presents evidence of the influence of the geographical zone in the levels of lead in blood, as was considered in other studies.30–34,40 In Pueblo Nuevo, there are no mines, and there are only a few industries, therefore it is necessary to continue investigating possible sources of lead contamination. The comparisons support the findings of other studies in that living next to mining zone30,34-41 or near an industry or laboratory where lead is used,39 as well as pike,9,22 influences the levels of lead in blood. The use of ceramic glazes also was identified as a factor associated with high concentrations of blood lead, which coincides with the results of Jim´enez-Guti´errez et al29 and Meneses-Gonz´alez et al.42 The consumption of canned food also showed statistical significance. Therefore, the types of food women eat and their origins need to be specified. The predictors for the levels of blood lead in pregnant women who showed persistence in the multivariate model coincide with those found in other studies, where notable factors of risk have been shown to be occupational exposure,16,20,43 the use of ceramic glazes for storing, eating or drinking food or drinks,29-40–42 and the habit of eating soil.9-22 The results suggest the implementation of measures for sanitary education so that pregnant women and their relatives could identify the sources of lead exposure and modify some habits associated with lead poisoning. The present study has some limitations in design that do not allow an identification of causal relationships because it 112

cannot determine the temporary dimension of the exposure. In spite of this, this cross-sectional study was an effort to quantify the lead exposure in pregnant women. Furthermore, this is the first study to examine blood lead levels in pregnant women in Durango State and one of the few ones conducted in Mexico. Therefore, the results of the present research can be used for comparison with future investigations and for the study of possible damages to the health of pregnant women at low levels of lead in blood. ********** This study was supported by the Council of Science and Technology for the State of Durango (COCYTED), Mexico. The authors thank the Secretary of Health of Durango for access to health institutions facilities. The authors also thank all the pregnant women, without whose cooperation the study would not have been completed. For comments and further information, address correspondence to Osmel La Llave Leon, Universidad Ju´arez del Estado de Durango, Instituto de Investigaci´on Cientifica, Av. Universidad y Fanny Anitua, Ap. postal 385, Durango, Dgo., Mexico E-mail: [email protected]

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Blood lead levels and risk factors in pregnant women from Durango, Mexico.

In this cross-sectional study the authors determined blood lead levels (BLLs) and some risk factors for lead exposure in pregnant women. Two hundred n...
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