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Hearing thresholds in children exposed to mercury in the prenatal period
Marilene Danieli Simões Dutra1, Marcia Cavadas, Iracina Maura de Jesus
1Institute of Public Health Studies, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil. lenadutra@uol.com.br
Insights
Prenatal mercury exposure did not significantly impact hearing in children aged 8-10 years. Audiometry results were within normal limits for both exposed and unexposed groups, indicating no discernible hearing threshold differences.
Area of Science:
- Environmental Health
- Pediatric Audiology
- Neurotoxicology
Background:
- Prenatal exposure to environmental toxins, such as mercury, can pose risks to child development.
- Auditory development is crucial for a child's overall cognitive and social progress.
Purpose of the Study:
- To assess hearing thresholds in children with documented prenatal mercury exposure.
- To determine if prenatal mercury exposure levels correlate with auditory function in children aged 8-10 years.
Main Methods:
- A cohort of 90 children (8-10 years) was divided into two groups based on umbilical cord mercury levels (≥8 µg/L vs. <8 µg/L).
- Pure-tone audiometry, speech reception threshold tests, and cord blood mercury level analysis were conducted.
- Questionnaires were used to gather additional participant information.
Main Results:
- The high-exposure group had a median cord blood mercury level of 14.63 µg/L, while the low-exposure group had a median of 4.88 µg/L.
- Both groups exhibited median hearing thresholds of 10 dB at 500 Hz, 1 kHz, and 2 kHz.
- No statistically significant differences in hearing thresholds were observed between the exposed and unexposed groups.
Conclusions:
- Children with prenatal mercury exposure demonstrated hearing thresholds within the normal range.
- Prenatal mercury exposure, at the levels studied, did not lead to measurable differences in hearing thresholds in children aged 8-10 years.
Purpose:
To evaluate hearing thresholds in children with a history of exposure to mercury during the prenatal period.
Methods:
Participants were 90 children of both genders with ages from 8 to 10 years, divided into two groups according to prenatal mercury exposure levels. The study group was composed by 57 children who had mercury levels in the umbilical cord equal or above 8 µg/L, and the comparison group comprised 33 children who had mercury levels in the umbilical cord below 8 µg/L. Investigation procedures included the application of a questionnaire, pure-tone audiometry, speech reception threshold, and mercury level analysis in cord blood collected at birth.
Results:
The study group showed a median mercury level in the umbilical cord of 14.63 µg/L, and the median threshold for 500 Hz, 1 kHz and 2 kHz in pure-tone audiometry was 10 dB for both ears. The comparison group had a median cord blood mercury level of 4.88 µg/L, and the median threshold for 500 Hz, 1 kHz and 2 kHz in pure-tone audiometry was 10 dB for both ears. When the hearing thresholds were compared, both by the tritonal mean and by each frequency separately, there were no significant differences between groups.
Conclusion:
The children had hearing thresholds within normal limits and there was no significant difference between the hearing thresholds of children exposed and not exposed prenatally to mercury.
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