Science of the Total Environment 473–474 (2014) 43–47

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Prenatal lead exposure and relationship with maternal exposure determinants in a public maternity hospital of La Plata, Argentina Enrique Martins a,⁎, Ana Varea a, María Apezteguía a, Horacio F. González a, Ana Girardelli b, Laura Sanchez Caro c, Mario Lobisuto d, Griselda Delgado c, Liliana Disalvo a a

Instituto de Desarrollo e Investigaciones Pediátricas (IDIP) “Prof. Dr. Fernando E. Viteri”, Hospital de Niños de La Plata (Ministerio de Salud/CIC-PBA), La Plata, Argentina Servicio de Toxicología, Hospital de Niños “Sor María Ludovica” de La Plata, Argentina Servicio de Neonatología, Hospital Interzonal General de Agudos “Gral. San Martín” de La Plata, Argentina d Servicio de Ginecología y Obstetricia, Hospital Interzonal General de Agudos “Gral. San Martín” de La Plata, Argentina b c

H I G H L I G H T S • • • •

We determined cord blood lead level and its relationship with maternal lead exposure. Cord blood lead level geometrical mean (GM) was 2.1 μg/dL. Lead-laden home dust and leaded water pipes might be the main sources of exposure. 25% of newborns might have some degree of risk for lead poisoning.

a r t i c l e

i n f o

Article history: Received 9 July 2013 Received in revised form 25 November 2013 Accepted 26 November 2013 Available online 19 December 2013 Keywords: Blood lead levels Umbilical cord blood Pregnancy Transplacental exposure

a b s t r a c t Prenatal lead exposure is a health hazard that may cause cognitive development impairments and other adverse effects in children. We conducted a cross sectional study analyzing cord blood lead levels (CBLL) of newborns and their relationship with maternal determinants of lead exposure. Mothers answered a questionnaire about sociodemographic, lifestyle habits and environmental characteristics. We used Mann–Whitney's test to compare CBLL geometrical means (GM) corresponding to the presence or absence of each lead exposure determinant, and Chi square test to study the relationship between CBLL and maternal lead exposure determinants. A total of 159 newborns participated in the study. CBLL GM was 2.1 μg/dL; and 25% of the participants had a measurable CBLL (LOQ = 3.3 μg/dl). Although the participants had several determinants of lead exposure, we only found a significant relationship with inside household determinants, such as presence of lead piping (p = 0.026), unplastered walls (p = 0.046) and peeling paint (p = 0.048). Our results show that CBLL GM was similar to that reported in several studies conducted around the world. However, 25% of the participants might have some degree of risk for lead poisoning. © 2013 Elsevier B.V. All rights reserved.

1. Introduction Lead is a toxic metal that contaminates air, water, soil, the food chain and ultimately man. Environmental lead originates mainly of human activities like fossil fuel burning, mining industry and several other industries (Agency for Toxic Substances and Disease Registry [ATSDR], 2007). Many environmental, socio-economic and lifestyle factors can be considered determinants of non-desirable blood lead levels (BLL) (Hertz-Picciotto et al., 2000; Lee et al., 2005), like living with

Abbreviations: CBLL, cord blood lead levels; BLL, blood lead levels; GM, geometrical mean; LOD, limit of detection; LOQ, limit of quantitation; OR, odds ratio; CI, confidence interval; MCT, measure of central tendency. ⁎ Corresponding author at: IDIP, Calle 63 N° 1069, 1900 La Plata Argentina. Tel./fax: +54 221 4535901x1767. E-mail address: enriquefl[email protected] (E. Martins). 0048-9697/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scitotenv.2013.11.128

occupationally exposed relatives, household lead piping, socioeconomically disadvantaged populations, and lead-laden home dust accumulation, among others. Certain inappropriate conditions like the presence of paint peelings, unplastered walls, dirt floors, and proximity to dirt streets, lead-related industries or intense traffic ways can contribute to the accumulation of lead in the home dust (Azayo et al., 2009; De Pietri et al., 2008; Gardella, 2001; Roy et al., 2009; Shen et al., 1997). In addition, certain habits of pregnant women have been related to a higher prenatal lead exposure, like active or passive smoking and alcohol or coffee drinking (Baghurst et al., 1987; Rhainds and Levallois, 1997). Low iron status has also been associated to a higher susceptibility to lead exposure (Bradman et al., 2001; Disalvo et al., 2009). In pregnant women, anemia (hemoglobin b 11 g/dL) has been used as a predictor of high BLL (Al-Jawadi et al., 2009). Current exposure (exogenous lead) might not be the sole contributor to pregnant women BLL, since another possible source of lead is bone store mobilization (endogenous

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lead). During physiological stress periods such as pregnancy, there is a larger demand of calcium that results in a greater bone mobilization; since lead stored in bone becomes bioavailable, endogenous lead can be an important contributor to BLL (Gulson et al., 2004). Considering that the half-life of lead in bone is approximately 30 years (Needleman, 2009), endogenous lead comes from exposures that occurred before pregnancy. Low-level lead exposure in pregnancy, though not harmful for the mother, can be of serious consequence to embryonic and fetal health because lead easily passes through the placenta (Goyer, 1990; Téllez-Rojo et al., 2004), and because the developing central nervous system is an especially sensitive target (Jones et al., 2010). During the prenatal stage of development, both embryo and fetus are very susceptible to environmental toxicants because there is intense cell division and differentiation. Maternal BLL near 10 μg/dL is associated with a greater probability of abortion, and even lower lead levels are associated with higher probability of preterm birth (ATSDR, 2007). In utero lead exposure has been associated to intrauterine growth retardation and low birth weight (Al-Saleh et al., 2008; Atabek et al., 2007; Chen et al., 2006; Srivastava et al., 2001), alterations in children's cardiovascular functioning (Gump et al., 2005), female offspring high blood pressure (Zhang et al., 2012), DNA methylation (Pilsner et al., 2009), and alterations in neonatal human behavior (Factor-Litvak et al., 1999; Gomaa et al., 2002; Schnaas et al., 2006; Shen et al., 1998). Umbilical cord blood sampling is an excellent non-invasive technique to estimate BLL during the prenatal period; it is considered as an estimation of the amount of lead accumulated by the fetus throughout pregnancy (Jedrychowski et al., 2008). In 1991, the Centers for Disease Control (CDC) adopted a threshold level of concern for children and women of childbearing age of 10 μg/dL (CDC, 1991). It was proposed as a risk management tool rather than a threshold for adverse effects (Bellinger and Bellinger, 2006). However, it is well documented that there are neurotoxic effects in children at BLL lower than 10 μg/dL, affecting cognition, memory and behavior (Canfield et al., 2003; Emory et al., 2003; Jedrychowski et al., 2009; Lanphear et al., 2005; Needleman, 2009). A pooled analysis by Lanphear et al. (2005) showed that lead-associated intellectual decrement was significantly greater for children with a maximal BLL of b 7.5 μg/dL than for those who had a maximal BLL of ≥7.5 μg/dL. It is also noteworthy that the central nervous system effects of lead on children seem not to be reversible (Bellinger, 2004). Given these findings, some authors recommended that the level of concern be lowered to 5 μg/dL (Landrigan et al., 2007) and even to 2 μg/dL (Gilbert and Weiss, 2006). Nowadays, the CDC have left out the term “level of concern” and adopted a new reference value of 5 μg/dL (CDC, 2012) based on the 97.5th percentile of the population BLL in children 1 to 5 years. Although not many, some studies regarding children environmental lead exposure have been conducted in Argentina. In a study at La Plata region in 2006, 10.6% of children between 6 months and 5 years of age had lead levels of N10 μg/dL (Disalvo et al., 2009). In a study in Cordoba City in 2012, the BLL GM ± SD found in children between 1 month and 14 years of age was 2.58 ± 0.30 μg/dL, and only 3.72% of these children had BLL superior to 10 μg/dL (Martınez et al., 2013), showing a significant reduction when compared to the results of a similar population studied in 1996 (Hansen et al., 1999) before leaded gasoline was phased out in Argentina. We have not found literature regarding prenatal lead exposure in Argentina. Therefore, we assessed cord BLL (CBLL) in a public maternity to determine whether there was any relationship between CBLL and maternal exposure to risk factors.

Argentina. Pregnant women were enrolled at admittance for delivery, between October 2010 and February 2011. Participants signed an informed consent form in the presence of a witness. The protocol was approved by the Comité Institucional de Revisión de Protocolos de Investigación (CIRPI), Instituto de Desarrollo e Investigaciones Pediátricas “Prof. Dr. Fernando E. Viteri”. 2.2. Sample preparation and analysis Four milliliters of cord blood were collected in lithium heparin vials (BD Vacutainer, Franklin Lakes, NJ, USA) by the midwife at delivery and were kept at − 70 °C until analysis. Cord blood lead was analyzed by Graphite Furnace Atomic Absorption Spectrophotometry (Varian AA 240Z, Programmable Sample Dispenser 120, Zeeman Effect background correction). Samples were diluted 1:10 with a triton X-100 solution (CALBIOCHEM, La Jolla CA, USA) which contained the matrix modifier (Ammonium phosphate monobasic, Sigma Aldrich Chemie, Steinheim, Germany). Internal quality control schemes were performed using a BIORAD Lyphochek Whole Blood Metals Control of 8.03 μg/dL, with a between run Coefficient of Variation (CV) of 6.8% and spiked samples of 5.1 μg/dL, with a between run CV of 7.4%. We participated of the external quality control program G-EQUAS (German External Quality Assesment Scheme, Erlangen, Germany, Environmental Medical Field). The difference between the concentration of the reference material and the concentration found using the analytic method ranged from 7.3% to 11.0%. The limit of detection (LOD) was 1.6 μg/dL and the limit of quantitation (LOQ) was 3.3 μg/dL. 2.3. Questionnaires

2. Materials and methods

We surveyed maternal lead exposure determinants with a questionnaire administered by a trained interviewer. To facilitate analysis, questions comprised four areas: sociodemographic, lifestyle, outside and inside household determinants of lead exposure. In the sociodemographic area, questions about residence site, family constitution, occupation, education, housing condition, access to water and sanitary services were included. Unsatisfied basic needs (UBN) is a direct method to identify critical shortages in a population and to characterize poverty. The indicator is directly related to four areas of people's basic needs (housing, sanitation, basic education and minimum income). UBN was determined following the Instituto Nacional de Estadísticas y Censos (INDEC) methodology (INDEC, 2003). In the lifestyle area, the determinants recorded were smoking, exposure to environmental tobacco smoke, and alcohol drinking. The following inside household lead exposure determinants were recorded: presence of peeling paint, unplastered walls, lead water piping, house under construction or repair during pregnancy, hobbies or lead-related activities within the house. The recorded outside household determinants (less than 100 m from the residence site) were: gas station, car repair workshop, car paint workshop, blacksmith's shop, lead battery workshop, bus stops, high traffic ways, rail road, dirt streets, smelters, petroleum distillery, garbage dump and contaminated creek. The following data were obtained from the mothers' and newborns' clinical records: mother's iron supplementation, gestational age, birth weight, size and cephalic perimeter. We determined the mothers' hemoglobin three to one days before delivery to assess the presence of anemia, using the World Health Organization (WHO) recommendation for the third trimester of pregnancy (blood hemoglobin b 11 g/dL) (WHO/UNICEF/UNU, 2001).

2.1. Design and study population

2.4. Statistical analysis

We conducted a cross sectional study in the public maternity of the Hospital Interzonal General de Agudos General San Martín, La Plata,

The statistical analysis was conducted with SPSS 18 for Windows. GM for CBLL was calculated since the variable was not normally

E. Martins et al. / Science of the Total Environment 473–474 (2014) 43–47

distributed. Values below the LOD were replaced with the LOD divided by the square root of two (CDC, 2013). We carried out a descriptive analysis of sociodemographic, lifestyle, outside and inside household lead exposure determinants for pregnant women. Mann–Whitney's test was used to compare CBLL GM corresponding to the presence or absence of each lead exposure determinant. Given that there is no safety threshold for CBLL, we established a cut point at the LOQ (3.3 μg/dL), considering any measurable amount of cord blood lead to be a health hazard. Chi-square test was used to study the relationship between the presence/absence of each lead exposure determinant with CBLL higher and lower than the cut point. Furthermore, a logistic regression model was used to adjust for potential confounding factors such as smoking, UBN, and outside household lead exposure determinants.

3. Results One hundred and sixty seven mothers accepted to participate in the study. Only 7.5% of term newborns had low birth weight (b2500 g) (WHO, 1977). Characteristics of mothers and newborns are shown in Table 1. CBLL was determined in 159 samples (8 samples were clotted). GM was 2.1 μg/dl (95% CI: 1.9–2.3; range, bLOD − 7.1 μg/dl); 25.7% of CBLL was N LOQ (3.3 μg/dL), 5.5% of CBLL was N5 μg/dl and none was N 10 μg/dL (Table 2). The mean ± SD hemoglobin (Hb) concentration of 158 samples was 10.9 ± 1.2 g/dl (95% CI: 10.7–11.1); 50% of mothers were anemic (Hb b 11 g/dL). No statistically significant differences were found comparing the GM of CBLL in anemic and non anemic mothers. Forty-four percent of the population lived in very humble households made of wood and corrugated zinc sheets; 34% of them lived in overcrowded conditions. Construction work was the most frequent job (37%). Regarding lifestyle habits, 29% of the mothers referred having smoked during pregnancy, mainly before knowing they were pregnant, though none of them continued with the smoking habit later on. Fifty seven percent of the participants were exposed to environmental tobacco smoke during the whole length of their pregnancy; 45% answered they had drunk a cup of alcohol occasionally during pregnancy, but none admitted drinking as a habit; 98.8% of the participant mothers attended periodic health examinations during pregnancy, and 80.7% took iron supplements. The most frequent outside household determinants of lead exposure were bus stops, dirt streets, car repair shops and high traffic ways. 90% of the interviewed mothers had at least 3 outside household determinants of lead exposure b 100 m from their homes.

Table 1 Descriptive characteristics of the interviewed mothers and their newborns. Participating mothers (n) Maternal age (range) in years UBN (%) Education level (%) Illiterate Up to Primary school, 7 years Secondary school complete, 12 years University Hb (g/dL) All the participants, n = 158 Non anemic, n = 79 Anemic, n = 79 Gestational age (weeks) Vaginal births (%) Birth weight (g) Sex (male) (%) Data are presented as mean ± SD or percentages.

167 25 ± 6 (15–45) 46.8 0.9 66.0 30.3 2.8 10.9 ± 1.2 11.9 ± 0.7 9.9 ± 0.8 38.7 ± 1.7 56 3292 ± 492 49

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Table 2 Categorization of cord blood lead levels.

bLOD LOD – LOQ LOQ — 5 μg/dL N5 μg/dL

N

Percentage

Cumulative percentage

55 66 33 9

33.7 40.4 20.2 5.5

33.7 74.2 94.5 100

LOD: 1.6 μg/dL; LOQ: 3.3 μg/dL.

Every mother referred having at least one inside household determinant of lead exposure, being house under construction or repairs the most frequent (52.1%). The presence of unplastered walls had a significantly different GM of CBLL (2.4 vs. 2.0 μg/dL; p = 0.047; Mann–Whitney's test). Chi-square test analysis of the relationship between CBLL higher than the cut point and lead exposure determinants resulted in a significant association for lead piping, peeling paint and unplastered walls. After applying a logistic regression model, only the presence of peeling paint and unplastered walls sustained a statistically significant association with CBLL (N3.3 μg/dL), indicating that the three inside household determinants might be related (Table 3). 4. Discussion Maternal lead exposure is an important potential risk for the fetus because lead can easily pass through the placenta (Goyer, 1990; Téllez-Rojo et al., 2004) and thus affect the embryo or fetus (ATSDR, 2007). The GM for CBLL was 2.1 μg/dL. Similar results have been recently obtained in countries with varying degrees of industrial and socioeconomic development and different environmental policies (Table 4). Several environmental or household factors and lifestyle habits determine pregnant women lead exposure. Although 90% of the participants had at least 3 current environmental lead exposure risk factors, CBLL did not reflect high maternal BLL during pregnancy. One possible explanation for this could be that there were low levels of environmental lead in the region of study. However, three inside household lead exposure determinants were associated with CBLL higher than the cut point, namely, unplastered walls, lead piping and paint peelings, although these factors might be related. These results could indicate that lead-laden home dust and drinking water are important sources of exposure for pregnant women in our region. It has been suggested that for children with BLL 5–9 μg/dL, multiple sources of exposure contribute but no single one predominates (Bernard and McGeehin, 2003). It seems likely that something similar could be happening with the exposure of the mothers in our population. Low socioeconomic status and poor educational level are determinants of higher risk of environmental lead exposure (Roy et al., 2009; Shen et al., 1997). Only ten percent of the study population was considered poor or indigent by the country's standards, and less than 1% did not complete primary school, indicating that these determinants affected a small part of the study population, having little influence over GM CBLL. Very few mothers drank alcohol during pregnancy, 29% smoked occasionally and a high proportion of participants were exposed to environmental tobacco smoke; although some studies have demonstrated a correlation between these habits and non desirable CBLL (Baghurst et al., 1987; Rhainds and Levallois, 1997), it was not reflected in our results. Our results show that 50% of the participants were anemic; however, no significant differences were found between CBLL of anemic vs. non anemic mothers, indicating that anemia was not a major determinant of non-desirable blood lead levels. This could be explained by the mild anemia found in the anemic participants. Another explanation could be that 80.7% of the participants reported taking iron supplements

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Table 3 Crude and linear regression adjusted OR (95% CI) of determinants associated with elevated CBLL (μg/dL). CBLL N 3.3

Variable

Lead piping Yes No Unplastered walls Yes No Peeling paint Yes No a

LRa OR (95% CI)

%

p

p

n

%

n

13 18

32.5 67.5

19 99

16.1 83.9

2.51 (1.01–5.72) 0.026

1.91 (0.76–4.79) 0.167

11 28

28.2 71.8

17 102

14.3 85.7

2.36 (0.99–5.60) 0.048

3.92 (1.51–10.14) 0.005

14 25

35.9 64.1

24 95

20.1 79.8

2.22 (1.00–4.90) 0.046

2.83 (1.19–6.73) 0.019

Adjusted by smoking, presence of UBN and presence of at least three outside household lead exposure determinants.

during current pregnancy. This prophylactic measure for anemia has been found to have a significant protective effect against the development of high CBLL (Al-Jawadi et al., 2009). Comparing our results with the CDC reference value for children less than 5 years of age, CBLL in our study population could be considered low, and it might be assumed that there is a low lead poisoning risk for the newborns. However, considering that there is no known threshold level for CBLL and that 25% of the newborns had a measurable amount of lead in their cord blood, this important fraction had some degree of lead poisoning risk. A limitation of our study is that we could not determine maternal blood lead. However, several studies have demonstrated a good correlation between maternal BLL throughout pregnancy and CBLL (Al-Jawadi et al., 2009; Graziano et al., 1990; Patel and Prabhu, 2009). Therefore, we can assume that CBLL reflects maternal BLL. Another limitation is that the study sample had some particular sociodemographic characteristics that might not represent those of the general population, e.g. the high proportion of participants with UBN might indicate that the study population was more vulnerable to lead exposure than the population with a better social condition. Finally, a greater sample size would have been necessary to find significant correlations for high CBLL, outside household determinants and lifestyle habits.

5. Conclusions The presence of a measurable amount of lead in cord blood in 25% of the study population might indicate some degree of risk for lead poisoning. Considering that few works have studied environmental lead exposure in our region and that this is the first to investigate prenatal lead exposure, our results could be useful for decision makers on environmental policies.

Table 4 Comparison of cord blood lead level measures of central tendency in various studies. MCT (μg/dL)a

Range (μg/dL)

n

Country

Reference

2.1† 2.55‡ 1.34§ 1.92‡ 2.1† 1.11‡ 2.4‡ 0.66† 1.6‡ 2.29† 1.29† 4.1‡ 1.29‡

b1.6–7.1 0.15–56.51 0.02–6.52 0.1–17.7 – b1.0–19.0 – b0.25–16.48 0–19.1 0.30–22.91 0.44–6.90 0.1–18.1 –

168 1578 43 1112 351 1466 102 294 205 370 444 150 308

Argentina Saudi Arabia Germany Belgium Canada Spain USA, Tennessee USA, Maryland India Iraq Poland Tanzania Taiwan

This study Al-Saleh et al., 2011 Gundacker et al., 2010 Koppen et al., 2009 Butler Walker et al., 2006 Llop et al., 2011 Jones et al., 2010 Wells et al., 2011 Patel and Prabhu, 2009 Al-Jawadi et al., 2009 Jedrychowski et al., 2009 Azayo et al., 2009 Lin et al., 2010

a

Crude OR (95% CI)

CBLL b 3.3

MCT reported by each author: †GM, ‡mean, §percentile 50.

Acknowledgments We greatly acknowledge the authorities and personnel of the Hospital Interzonal General de Agudos “Gral. San Martín” of La Plata. EM received a Carrillo-Oñativia Scholarship granted by the Comisión Nacional Salud Investiga. Ministerio de Salud y Ambiente de la República Argentina. The study was funded by Instituto de Desarrollo e Investigaciones Pediátricas (IDIP) “Prof. Dr. Fernando E. Viteri”, Hospital de Niños de La Plata (Ministerio de Salud/CIC-PBA). The authors declare they have no actual or potential competing financial interests.

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Prenatal lead exposure and relationship with maternal exposure determinants in a public maternity hospital of La Plata, Argentina.

Prenatal lead exposure is a health hazard that may cause cognitive development impairments and other adverse effects in children. We conducted a cross...
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