Exposures to Heavy Metals among Pregnant Women of Thailand: Pooled Urine Sample Analysis Open Access

Abstract

 

Background Pregnant women are at risk from heavy metals exposure due to physiologic changes, resulting in adverse pregnancy outcomes. Pooling approach is an approach which is beneficial in reducing financial and laboratory burden in limited-resource settings. The study aimed to assess background exposure of heavy metals among pregnant women and to evaluate the differences of urinary cadmium and lead level across geographic regions and across trimesters of pregnancy by using pooled sample analysis.  

Methods We collected urine samples from all nationalities pregnant women who attended the ANC clinics during two weeks in six hospitals representing six different regions of Thailand. We asked clinical staff to split 1-ml of excess urine from routine ANC care into 50-ml tubes by trimesters. The samples were analyzed for cadmium and lead level as well as cotinine as biomarkers of tobacco smoking which might be a potential source of exposure.  

Results Fifty-two pools samples of 2,112 individual pregnant women were collected by trimesters and by hospitals. Geometric mean for urinary cadmium and lead were 0.63±1.14 ng/mL and 0.82±1.07 ng/mL respectively. Log-transformed cadmium and lead levels were found statistical differences across the hospitals (p-value <0.0001 and 0.0014). The log-transformed urinary cadmium and lead showed the decreasing trends as trimester decreases, but they did not show statistically significant (p-value 0.66 and 0.28 respectively). Furthermore, there was a positive linear relationship between log-transformed urine lead and cotinine (p-value <0.001, r=0.38).  

Conclusions Our study is the first study demonstrating the pattern of cadmium, lead and cotinine exposure by using pooled urine approach among Thai pregnant women. The results indicate that environmental tobacco exposure might be a potential source of lead exposure whereas diet might be a primary source of cadmium exposure among pregnant women in Thailand. Large-Scale human biomonitoring should be developed by using pooling approach to integrate this fruitful data into national public health surveillance. 

Table of Contents

Table of Contents 

I. Background and Significance.......................................................................................................1 

Source of exposure to heavy metal inPregnancy....................................................................................................1 

Physiologic changes in pregnancy.............................................................................................................................3 

Effects of heavy metals in pregnancy and fetal outcomes....................................................................................4 

Human biomonitoring................................................................................................................................................4 

Pooled urine samples...................................................................................................................................................7 

Hypotheses....................................................................................................................................................................9 

II. Methods........................................................................................................................................9 

Participants recruitment.............................................................................................................................................10 

Exposure assessment..................................................................................................................................................11 

Outcome assessment..................................................................................................................................................11 

Statistical analysis.........................................................................................................................................................13 

III. Results........................................................................................................................................14 

Basic demographic data..............................................................................................................................................14 

Exposure, confounder and outcome summary......................................................................................................14 

Primary outcome.........................................................................................................................................................16 

Secondary outcome.....................................................................................................................................................17 

Correlation....................................................................................................................................................................17 

IV. Discussions.................................................................................................................................17 

Feasibility......................................................................................................................................................................17 

Outcome interpretation..............................................................................................................................................18 

Limitations....................................................................................................................................................................23 

Conclusions and Recommendations................................................................................................25 

Conclusions..................................................................................................................................................................25 

Recommendations for future research.....................................................................................................................26 

Policy recommendations.............................................................................................................................................26 

References.........................................................................................................................................28 

Tables and Figures...........................................................................................................................33 

Appendices........................................................................................................................................50 

About this Master's Thesis

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School	Rollins School of Public Health
Department	Environmental Health
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Environmental Health
Keyword	Heavy Metals Pregnant women Pooled urine Thailand
Committee Chair / Thesis Advisor	Ryan, P. Barry, Emory University
Committee Members	Tolbert, Paige, Emory University Panuwet, Parinya, Emory University
Partnering Agencies	Non-US governmental agency (e.g., Minister of Health in Haiti)

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