Applied Epidemiology and Meta-Research

ECPI

A Systematic Review of Phthalate epidemiology studies

Phthalates are a group of synthetically produced compounds used in cosmetics, flooring adhesives, medical tubing, toys, food packaging materials etc. Metabolites and the parent compounds are detectable in urine and serum samples of the general population. From the multitude of phthalates that exist, eight  (normally fewer and in varying combinations) are measured in human urine or plasma (diethyl phthalate or DEP, di-butyl phthalate or DBP, di-n-butyl phthalate or DiBP, butyl benzyl phthalate or BBzP, di-n-octyl phthalate or DOP, di-isodecyl phthalate od DIDP, di-isononylphthalate or DINP, and di-2-ethylhexyl phthalate or DEHP). In many instances the parent compound is not measured but its metabolite(s). Because of their relatively short half-life in the human body the time between exposure and sampling strongly affects the concentrations in the biomonitoring sample.

A wide range of health outcomes have been studied with respect to their correlation with varying sets of phthalates. These include, sperm motility, steroidogenesis, precocious puberty, birth weight, infant development, asthma, hypospadias, breast cancer, congenital heart defects, endometriosis etcetera.

The epidemiological studies vary in study design, including cross-sectional studies, cohort studies and case-control studies. The hypotheses mentioned in the papers generally do not specify which specific phthalate is thought to be associated with the health outcome. Many studies utilize already existing databases such as the United States National Health And Nutrition Examination Survey (NHANES) or existing birth cohort studies.

The combination of these factors has resulted in an extremely heterogenic and complex literature base with positive and negative findings that are difficult to interpret. A Systematic Review therefore is warranted, but it also requires a thorough understanding of the research. We believe that a reliable systematic review of the phthalate literature can only be made if the underlying research protocols are included in the analysis. We therefore will contact the corresponding author of every selected article and request a copy of the protocol and ask if he/she is willing to participate in a survey about how the research was conducted.

The project has the objective to conduct a Systematic Review of published articles and protocols of epidemiological studies on phthalates and health. The Systematic Review will:

  1. assess the completeness of reporting of these articles
  2. assess the quality of the underlying protocols
  3. assess the concordance between the published articles and underlying protocols
  4. assess the determinants of protocol provision

The project has received funding from the European Council of Plasticisers and Intermediates and is conducted by Gerard Swaen, PhD and prof. Maurice Zeegers from the Maastricht University.

Research group

Gerard Swaen, PhD
Prof. Maurice Zeegers 

Contact

Gerard Swaen, PhD
E: g.swaen@maastrichtuniversity.nl