The Peruvian Region of Tacna has the highest prevalence of macrosomia (15%), but also the highest arsenic (As) concentration in tap water. The consumption of tap water contaminated with arsenic is associated with low birth weight [1]. To address this discrepancy in this Region, the objective of this study is to evaluate the averages of arsenic concentration in tap water with different reproductive outcomes.
Birth records were obtained from the Perinatal Information System from the Hospital Hipolito Unanue, Tacna. There were 60,984 births recorded from January 2000 to April 2018. Of these, 43,823 live newborns from single pregnancies of women between 15 and 49 years of age were selected. Arsenic concentration in tap water per district was obtained through the Tacna’s Regional Direction of Health in 2010, 2012, 2014, 2015 and 2016. These values were expressed as total means per district and assigned according to mother district of residence code available in the database.
Births were grouped by arsenic concentration (≤10 μg/L, >10 – 50, >50 – 100 and > 100 μg/L). Birthweight, preterm birth, macrosomia (≥4000 g), small for gestational age (SGA), large for gestational age (LGA) [2] and Low-Apgar-Score (LAPS, <7) was compared between groups with different arsenic concentrations by ANOVA or Chi-square test. Linear and Logistic-regression analysis were also performed and adjusted by co-variables. Statistical analysis was done using STATA.15. Study was approved by the Universidad Peruana Cayetano Heredia IRB (SIDISI 103426).
In Table 1 is observed that districts with highest arsenic concentration in tap water has the lowest rates of SGA. Ciudad Nueva shows the highest prevalence of macrosomia and LAPG. In exposure groups, arsenic was not related to birth outcomes, except for SGA, which appears to have a protective effect OR (95% CI) 0.46 (0.27, 0.78).
Table 1:
Birthweight, prevalence of preterm births, small for gestational age (SGA), Large for gestational age (LGA), macrosomia and low Apgar at first minute according to levels of arsenic in drinking water. Summary statistics per district, arsenic level and of the whole population. One-way ANOVA of mean birthweight and Pearson’s Chi-squared of prevalence between districts. Birthweight between arsenic levels was assessed by linear regression and Odds-Ratio for Preterm Birth, Macrosomia, SGA and LGA and low Apgar score at first minute were analyzed by logistic regression. Models were adjusted by altitude of residence, BMI, parity, antenatal care, gestational diabetes, urinary tract infection and pre-eclampsia diagnosis during pregnancy.
| As level (ug/L) | Province | District | N | Birthweight | Preterm | SGA | LGA | Macrosomia | Apgar1<7 |
|---|---|---|---|---|---|---|---|---|---|
| ≤10 | Tacna | - | - | - | - | - | - | - | - |
| Candarave | Camilaca | 40 | 3306 ± 574 | 2.50 | 25.00 | 12.50 | 10.00 | 12.50 | |
| Jorge Basadre | Locumba | 161 | 3495 ± 625 | 4.97 | 6.83* | 21.12 | 16.15 | 3.73 | |
| Tarata | Sitajara | 4 | 3304 ± 651 | 25.00 | 25.00 | 0.00 | 0.00 | 0.00 | |
| Ticaco | 21 | 3226 ± 651 | 14.29 | 19.05 | 4.76 | 4.76 | 9.52 | ||
| Level Total | 226 | 3426 ± 623 | 5.75 | 11.50 | 17.70 | 13.72 | 5.75 | ||
| β-coeff / OR (95%IC) | Ref. | Ref. | Ref. | Ref. | Ref. | Ref. | |||
| >10 – 50 | Tacna | Alto de la Alianza | 4582 | 3488 ± 546 | 5.46 | 7.38 | 19.03 | 14.19 | 3.71 |
| Calana | 242 | 3463 ± 571 | 4.13 | 8.26 | 19.01 | 11.98 | 2.07 | ||
| Ciudad Nueva | 4990 | 3523 ± 555 | 5.45 | 6.79 | 20.58 | 17.52* | 4.83* | ||
| Pachía | 122 | 3430 ± 490 | 6.56 | 9.02 | 15.57 | 9.84 | 2.46 | ||
| Pocollay | 1046 | 3510 ± 546 | 5.26 | 7.07 | 19.98 | 15.11 | 3.25 | ||
| Candarave | - | - | - | - | - | - | - | - | |
| Locumba | - | - | - | - | - | - | - | - | |
| Tarata | Estique-Pampa | 2 | 4000 ± 226 | 0.00 | 0.00 | 50.00 | 50.00 | 0.00 | |
| Susapaya | 11 | 3119 ± 711 | 0.00 | 27.27 | 9.09 | 9.09 | 9.09 | ||
| Tarucachi | 8 | 3219 ± 487 | 0.00 | 12.50 | 12.50 | 12.50 | 0.00 | ||
| Level Total | 11003 | 3504 ± 551 | 5.41 | 7.14 | 19.78 | 15.69 | 4.13 | ||
| β-coeff / OR (95%IC) | 45.63 (−28.16 / 119.43) | 0.91 (0.47 / 1.77) | 0.59 (0.37 / 0.95) | 1.03 (0.71 / 1.50) | 1.12 (0.73 / 1.72) | 0.76 (0.39 / 1.46) | |||
| >50–100 | Tacna | Tacna | 31625 | 3467 ± 555 | 6.22 | 7.49 | 19.00 | 13.75 | 4.02 |
| Candarave | - | - | - | - | - | - | - | - | |
| Jorge Basadre | - | - | - | - | - | - | - | - | |
| Tarata | Héroes Albarracín | 10 | 3389 ± 595 | 0.00 | 10.00 | 10.00 | 10.00 | 10.00 | |
| Level Total | 31635 | 3467 ± 555 | 6.21 | 7.49 | 19.00 | 13.75 | 4.02 | ||
| β-coeff / OR (95%IC) | 26.68 (−46.88 / 100.25) | 0.98 (0.50 / 1.90) | 0.58 (0.37 / 0.93) | 1 (0.68 / 1.45) | 1.01 (0.66 / 1.54) | 0.72 (0.37 / 1.38) | |||
| >100 | Tacna | Inclán | 154 | 3514 ± 455 | 7.14 | 1.30 | 15.58 | 11.04 | 5.84 |
| Palca | 50 | 3373 ± 551 | 2.00 | 16.00* | 15.57 | 14.00 | 4.00 | ||
| Sama | 136 | 3509 ± 529 | 3.68 | 8.82 | 18.38 | 14.71 | 5.88 | ||
| Candarave | Candarave | 96 | 3277 ± 532 | 11.46 | 9.38 | 10.42 | 6.25 | 10.42 | |
| Cairani | 35 | 3329 ± 438 | 5.71 | 11.43 | 5.71 | 5.71 | 0.00 | ||
| Curibaya | 9 | 3411 ± 585 | 22.22 | 0.00 | 11.11 | 11.11 | 0.00 | ||
| Huanuara | 13 | 3475 ± 396 | 15.38 | 0.00 | 15.38 | 7.69 | 7.69 | ||
| Quilahuani | 21 | 3507 ± 379 | 4.76 | 4.76 | 14.29 | 4.76 | 4.76 | ||
| Jorge Basadre | Ilabaya | 117 | 3327 ± 613 | 11.97 | 14.53 | 17.95 | 7.69 | 4.27 | |
| Ite | 149 | 3503 ± 567 | 7.38 | 4.03 | 20.81 | 15.44 | 4.70 | ||
| Tarata | Tarata | 168 | 3304 ± 651 | 7.74 | 10.12 | 10.12 | 10.12 | 6.55 | |
| Estique | 11 | 3532 ± 416 | 0.00 | 9.09 | 27.27 | 9.09 | 0.00 | ||
| Level Total | 959 | 3413 ± 558 | 7.61 | 8.03 | 15.43 | 10.95 | 5.63 | ||
| β-coeff / OR (95%IC) | 9.77 (−72.14 / 91.69) | 1.16 (0.56 / 2.39) | 0.46 (0.27 / 0.78) | 0.82 (0.53 / 1.26) | 0.78 (0.48 / 1.27) | 0.95 (0.46 / 1.96) | |||
| Total | 43823 | 3475 ± 555 | 6.04 | 7.43 | 19.11 | 14.18 | 4.09 | ||
p<0.05 for ANOVA and Chi-square test. For linear and logistic regression, β-coeff or OR with 95%IC is showed. N=number of observations.
Despite the high rate of macrosomia and high geogenic-arsenic, there was no adverse effect of arsenic contamination with birth outcomes. Arsenic has been present in the region for more than 7000 years, thus the population living there could be protected against adverse effects of arsenic, through genetic mechanisms involving polymorphisms, like the as3mt gene, as observed in Aymara populations in Argentina [3], which are specially beneficial during pregnancy [4]. These favor the metabolism of arsenic into less-toxic metabolites. However, Aymara ethnicity maybe also a condition for higher birthweights as previously suggested [5].
Although no major health threat was observed in this particular group this remains a major health problem for other vulnerable groups like pre-scholar children. It is needed further research assessing the effects of arsenic in reproductive outcomes in relation to genetics, ethnicity and metabolism of arsenic in the population residing in Tacna.
Acknowledgements
Funding Statement: Research reported in this publication was supported by the NIH Fogarty International Center, National Institutes of Environmental Health Sciences, National Cancer Institute, Centers for Disease Control and the NIH under Award Number U01 TW0101 07 (Supplementary funds). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Footnotes
Disclosure Statement
Authors declare no conflict of interest.
References
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