Associations Between Ambient PM_2.5 and Thyroid Hormones in Pregnant Persons in Puerto Rico

Area of Science:

• Environmental Health
• Endocrinology
• Reproductive Health

Background:

• Puerto Rican pregnant individuals are a vulnerable population facing socioeconomic and environmental disparities.
• Fine particulate matter (PM2.5) air pollution is a significant environmental exposure.
• Thyroid hormones are crucial for maternal and fetal development.

Purpose of the Study:

• To investigate the association between PM2.5 exposure and thyroid hormone levels (TSH, T3, T4, FT4) during pregnancy.
• To examine potential variations in these associations based on the timing of exposure during gestation.
• To explore dose-response relationships between PM2.5 and thyroid hormone levels.

Main Methods:

• Utilized data from 1040 participants in the PROTECT cohort study.
• Linked participant locations to EPA air quality data for PM2.5 concentration assessment.
• Analyzed thyroid hormone levels at two gestational visits (weeks 16-20 and 24-28).

Main Results:

• PM2.5 exposure showed positive associations with maternal T3, T4, and FT4 levels, but not TSH.
• Timing of exposure influenced the associations: T3 stronger later in pregnancy, T4/FT4 stronger earlier.
• Nonlinear dose-response relationships were observed, indicating potential hormone-specific thresholds.

Conclusions:

• Findings support links between altered thyroid hormones and adverse birth outcomes.
• Air pollution may disrupt maternal thyroid function, with implications for fetal development.
• Further research is needed to understand mechanisms and develop interventions to mitigate risks.