Exposure to metals such as nickel, arsenic, cobalt and lead may disrupt a woman’s hormones during pregnancy, according to a Rutgers study.
The study appears in the journal Environment International.
Exposure to metals has been associated with problems at birth such as preterm birth and low birth weight in babies, and preeclampsia in women. However, little is known about how metals exposure can lead to such problems.
This new research shows that some metals may disrupt the endocrine system, which is responsible for regulating our body’s hormones. These disruptions may contribute to children’s later health and disease risk.
“A delicate hormonal balance orchestrates pregnancy from conception to delivery and perturbations of this balance may negatively impact both mother and fetus,” said lead author Zorimar Rivera-Núnez, an assistant professor in the Department of Biostatistics and Epidemiology at the Rutgers School of Public Health.
The researchers analyzed blood and urine samples from 815 women enrolled in the Puerto Rico Test site for Exploring Contamination Threats (PROTECT) study.
Initiated in 2010, PROTECT is an ongoing prospective birth cohort studying environmental exposures in pregnant women and their children around the northern karst zone, which include urban and mountainous rural areas of Puerto Rico.
They found that metals can act as endocrine disruptors by altering prenatal hormone concentrations during pregnancy. This disruption may depend on when in the pregnancy the mother was exposed.
Prenatal exposure to metals can have enormous consequences even beyond health at birth. Alterations in sex-steroid hormones during pregnancy have been associated with inadequate fetal growth, which leads to low birthweight. Birth size is strongly associated with a child’s growth and risk of chronic diseases, including obesity and breast cancer.
“Puerto Rico has one of the highest rates of Superfund sites of any of the U.S. jurisdictions with 18 active sites, which can contribute to the higher rates of exposure to toxic metals,” said Rivera-Núnez.
Among pregnant women, metal exposure is higher in those living in Puerto Rico than in those in the continental United States.
“This is important because, compared to the U.S. overall, women in Puerto Rico have significantly higher rates of preterm birth [nearly 12 percent] and other adverse birth outcomes. Additionally, exposure to environmental pollution is exacerbated by extreme weather events, such as hurricanes, droughts and flooding, which may result in elevated exposures to Superfund sites,” she added.
According to the study authors, future research should investigate how changes in markers of endocrine function affect birth and other health outcomes. Future studies also should look at essential metals in relation to maternal and fetal health, and metals as mixtures in relation to markers of endocrine function.
In recent decades, a trend toward earlier onset of puberty among boys and girls has been described [1,2,3,4,5,6,7,8,9]. These trends in the timing of puberty, a period of physical and psychological development, have raised concerns regarding the potential impact of environmental factors, including endocrine disrupting chemicals (EDCs) [10,11,12,13].
Exposure to EDCs prenatally and at the prepubertal stage are thought to play a role in altered pubertal timing, possibly via their estrogenic or anti-androgenic effects and disruption of normal homeostatic control of the hypothalamic-pituitary-gonadal (HPG) or hypothalamic-pituitary-adrenal (HPA) axis [13,14,15,16,17,18,19,20,21,22,23,24,25,26].
Some metals and metalloids, such as cadmium (Cd), lead (Pb), mercury (Hg), and arsenic (As), are non-essential xenobiotics that are known to be harmful to human health [27,28,29,30]. These non-essential metal(loid)s are persistent in the environment and children’s exposure to them is nearly ubiquitous .
Several other metals, such as chromium (Cr), copper (Cu), manganese (Mn), molybdenum (Mo), selenium (Se) and zinc (Zn), are essential for optimal health but may be harmful at insufficient or excessive levels [32,33,34,35,36]. A number of metal(loid)s are reproductive toxicants and have endocrine disrupting properties which interfere with many aspects of endocrine functions through interacting with hormone secretion, transport and binding receptors as well as genomic expression and epigenetic modification [19, 37,38,39,40,41,42,43].
Some of these proposed mechanisms of actions are common to different metals, such as binding with estrogen receptor (Cd, As, Pb) and increasing lipid peroxidation (Pb, Hg), while others are specific, for instance, stimulation or inhibition of nuclear transcription activity (As) and inhibition of LH secretion (Pb) .
Many human and animal studies have focused on elucidating the reproductive effects associated with heavy metal and metalloids, such as Cd, Pb, Hg, and As. Though many studies on Cd were either cross-sectional and/or conducted on adults, there has been some consistency of findings with regard to the positive relationship between male and female Cd exposure and testosterone concentrations [45,46,47,48,49,50,51,52,53].
In a group of men with no occupational exposure, positive associations between blood Pb concentrations and testosterone and/or estradiol levels were reported [46, 48, 50]. In longitudinal studies of children’s reproductive development, childhood Pb exposure was related to later pubertal onset [54, 55] and delayed sexual maturation  in Russian boys in Chapaevsk, Russia.
In contrast, we have shown early life exposure to Pb was associated with delays in pubertal development in girls but not boys in Mexico City [21, 22]. Hg was found to be associated with increased estradiol levels in both males and females from a small residential population in Cambodia , which was in agreement with a previous study among women with repeated miscarriages .
A recent study of As exposure through well water consumption in Taiwan suggested that As may impart an increased risk of erectile dysfunction through a reduction of circulating testosterone .
Although less attention has been given to the other metals in the past, a growing body of evidence suggests that certain essential or trace metals, including Cu, fluoride (F), Mn, Mo, and Se can also have adverse effects on male reproduction [60,61,62,63].
In addition, most reports on the male reproductive effects of metals are from experimental animal, epidemiological, and occupational studies usually involving high doses not commonly encountered by children.
Due to the widespread exposure of humans and known adverse effects related to essential and non-essential metal exposure, concern is growing that low-level exposure may also adversely affect reproductive developmental outcomes in boys.
Moreover, only a few studies have investigated the cross-sectional relationships in boys, with the exception of two recent longitudinal studies in Russia and Mexico [56, 63], and none have examined exposure during in utero development and subsequent hormone levels during puberty, a time at which steroid hormones play an essential role in reproductive development [11, 64,65,66].
Therefore, the present study assessed whether in utero and prepubertal exposure to metals at relatively low doses altered reproductive hormone levels or timing and progression of sexual maturation in boys.
We extended the limited metals studied on this topic and examined both essential and non-essential metals in relation to reproductive hormone concentrations and progression of sexual maturation in boys from ages 8–14 years to 10–18 years.
reference link : https://ehjournal.biomedcentral.com/articles/10.1186/s12940-020-00672-0
More information: Zorimar Rivera-Núñez et al, Association of biomarkers of exposure to metals and metalloids with maternal hormones in pregnant women from Puerto Rico, Environment International (2020). DOI: 10.1016/j.envint.2020.106310