Relationships of Lead, Mercury and Cadmium Levels with the Timing of Menarche among Korean Girls

Effects of Blood Lead Levels <10 µg/dL in School-Age Children and Adolescents: A Scoping Review

CONTEXT

Lead exposures among school-age children are a major public health issue. Although the harmful effects of lead exposure during the first years of life are well known, there is not as much understanding of the effects of low levels of lead exposure during later childhood.

OBJECTIVES

To review the effects of blood lead levels (BLLs) <10 µg/dL in school-age children and adolescents.

DATA SOURCES

We searched Medline, Embase, Global health, CINAHL, Scopus, and Environmental Science Collection databases between January 1, 2000, and May 11, 2023.

STUDY SELECTION

We included peer-reviewed English-language articles that presented data on the effects of BLLs <10 µg/dL in individuals ages 5 through 18 years.

DATA EXTRACTION

Data on country, population, analytic design, sample size, age, BLLs, outcomes, covariates, and results were extracted.

RESULTS

Overall, 115 of 3180 screened articles met the inclusion criteria. The reported mean or median BLL was <5 µg/dL in 98 articles (85%). Of the included articles, 89 (77%) presented some evidence of an association between BLLs <10 µg/dL during school age and detrimental outcomes in a wide range of categories. The strongest evidence of an association was for the outcomes of intelligence quotient and attention-deficit/hyperactivity disorder diagnoses or behaviors.

LIMITATIONS

Few articles controlled for BLLs at age <5 years, limiting conclusions about the relation between later BLLs and outcomes.

CONCLUSIONS

BLLs <10 µg/dL in school-age children and adolescents may be associated with negative outcomes. This review highlights areas that could benefit from additional investigation.

Association of blood metal exposure with age at menarche in Korean women: KNHANES (2008-2017)

Humans are exposed to metals in their daily lives and this metal exposure is responsible for various adverse health effects. Delayed pubertal development has been suggested as an adverse outcome of metal exposure; however, evidence in nationally representative populations, especially in Asia, is limited. We evaluated the association of blood cadmium (Cd), lead (Pb), and mercury (Hg) levels with the age at menarche in Korean females whose blood heavy metals were measured as part of the Korean National Health and Nutrition Examination Survey (KNHANES) 2008-2017. Among the females 16 years of age or older, all measured heavy metals in blood, i.e., Cd, Pb, and Hg, were positively associated with age at menarche. These associations remained significant in a model adjusted for age, survey year, income, education, body mass index, smoking history, and menopausal status as covariates (β: 0.10, 95% confidence interval (CI): 0.03-0.18 for Cd; β: 0.17, 95%CI: 0.06-0.27 for Pb; β: 0.12, 95%CI: 0.05-0.19 for Hg). When the population was separated by age group at the time of the survey, the significance between heavy metal levels and age at menarche became inconsistent, but the general trends were similar. Among those in their 20s and 40s, blood Cd showed a significant association, while Pb was significant among those in their 40s and 50s. A similar trend was observed in the sensitivity analysis in the girls aged 10-15 years at the time of the survey. Blood Cd levels were associated with decreased odds of precocious menarche (OR: 0.57, 95%CI: 0.31-1.03). Delayed menarche is a risk factor for cardiovascular and chronic kidney diseases in later life; hence, public health implication of heavy metal exposure warrants a public health attention.

Exposure to metals and the disruption of sex hormones in 6-19 years old children: An exploration of mixture effects

BACKGROUND

Individual metals have been linked to sex hormones disruption, but the associations of metals mixture are rarely examined among children.

METHODS

A total of 1060 participants of 6-19-year-old who participated in the National Health and Nutrition Examination Survey (2013-2016) were included. Eighteen metals were quantified in the whole blood and urine. Sex hormones were measured in serum, including total testosterone (TT), estradiol (E₂), and sex hormone binding globulin (SHBG). In addition, free androgen index (FAI) and the ratio of TT to E₂ were calculated. Bayesian kernel machine regression and latent class analysis were performed to assess the associations of metals mixture and exposure patterns of metals at varied levels with sex hormones while adjusting for selected covariates. All analyses were conducted by sex-age and sex-puberty groups to explore the potential sex-dimorphic effects.

RESULTS

Exposure to metals mixture was associated with elevated levels of FAI and E₂ among 12-19 years old girls. Moreover, the exposure pattern of metals that was characterized by high levels of blood and urinary cadmium, blood manganese, and urinary cobalt was associated with elevated E₂ and reduced TT/E₂ levels among girls of 12-19 years old. However, the associations of metals mixture with sex hormones were overall nonsignificant among boys. Nevertheless, metals exposure pattern that was characterized by high levels of blood lead, urinary barium, strontium, and lead but comparatively low levels of the other metals was consistently associated with reduced levels of FAI and E₂ but elevated levels of TT/E₂ and SHBG among boys of 12-19 years old.

CONCLUSION

Metals mixture and exposure patterns that were dominated by high levels of certain metals were associated with sex hormones imbalance among 12-19 years old children in a sex-dimorphic pattern, with the identified individual metals that drove the associations of metals mixture varied by sex.

Manganese and Lead Exposure and Early Puberty Onset in Children Living near a Ferromanganese Alloy Plant

Manganese (Mn) and lead (Pb) have been associated with the deregulation of the neuroendocrine system, which could potentially favor the appearance of precocious puberty (PP) in environmentally exposed children. This study aims to evaluate the exposure to Mn and Pb and their potential effects in anticipating puberty in school-aged children living near a ferromanganese alloy plant in Bahia, Brazil. Toenail, occipital hair and blood samples were collected from 225 school-aged children. Tanner’s scale was used for pubertal staging. Mn in blood (MnB), toenail (MnTn) and hair (MnH) and blood lead (PbB) levels were measured by graphite furnace atomic absorption spectrometry. Puberty-related hormone concentrations were determined by chemiluminescence. The age at which girls’ breasts began to develop was inversely correlated with weight-for-age, height-for-age and BMI-for-age Z-scores (p < 0.05); pubarche also had similar results. Mn biomarker levels did not present differences among pubertal classification nor among children with potential PP or not. Furthermore, Mn exposure was not associated with the age of onset of sexual characteristics for either girls or boys. However, PbB levels were positively correlated with boys’ pubic hair stages (rho = 0.258; p = 0.009) and associated with the age of onset of girls’ pubarche (β = 0.299, 95%CI = 0.055−0.542; p = 0.017). Testosterone and LH concentrations were statistically higher in boys with an increased PbB (p = 0.09 and p = 0.02, respectively). Prospective studies are needed to better assess the association between exposure to Mn and Pb and the early onset of puberty.

Age at Menarche in Urban Girls Exposed to Lead in the Copper Basin, Poland

Lead negatively affects human growth and development. In this research, we aimed to assess the effect of elevated blood lead level on age at menarche (AM), controlling for body mass index (BMI) and estimated fatness. The sample included 490 girls aged 7−16 examined in Polkowice town (Copper Basin, Poland) in 2008. Measurements included height, weight, skinfold thicknesses and estimated percentage of body fat. AM was assessed using the status quo method. Blood samples were taken for lead level assessment. Two groups were defined based on the median blood lead level for the total sample of children (3.7 µg/dL). Logistic regression models were used to assess the association between AM and independent variables. The results indicated that menarche in the higher blood lead level group was significantly later compared to the lower blood lead level group (p < 0.01). This relationship remained only marginally significant when BMI (p < 0.10), sum of skinfolds (p < 0.09) or percentage of fat (p < 0.08) were controlled. The results revealed that a lower blood lead level (3.7 µg/dL) than the currently acceptable threshold (5 µg/dL) is related to a later AM; however, this relationship is moderated by body fatness, which may decrease its significance.