Research Projects

Research on estrogenic activity in cling wrap plastics – Prof Christiaan de Jager

Research on estrogenic activity in cling wrap plastics – Prof Christiaan de Jager

Prof Christiaan de Jager

Prof Tian De Jager

Project title

Nonylphenol, bisphenol-A, selected phthalates and total estrogenic activity in cling wrap plastics commercially available in South Africa

Project description

Food is a major exposure route for endocrine disrupting chemicals (EDCs).  Typical food contaminants for example pesticides, dioxins, PCTs, PBDEs, methylmercury, lead and arsenic are well documented in food, with relatively high international public and regulatory awareness.  Nonylphenol (NP) is known for its estrogen mimicking properties and is used in the manufacturing of surfactants and plastics.  NP may leach from certain brands of clingwrap into the food when heated, increasing the risk of exposure.  Bisphenon-A (BPA) known to be estrogenic and potentially carcinogenic is also found in plastics and food packaging material.  Phthalates are a group of industrial chemicals with many commercial uses which include paints, personal care products and most commonly as plasticizers in medical devices, food packaging material.  The so-called ‘phthalate syndrom’ may be associated with testicular cancer.  There is worldwide consensus that cancer is a disease that is mainly caused by environmental factors in 90& of cases.  Therefore this study proposes to investigate the presence, concentration and estrogenic activity of the mixture of plasticisers (NP, BPA and selected phthalates) in common cling wraps used for domestic and commercial use in South Africa.  A human health risk assessment will be done to calculate the cancer risk.

A survey will be done to determine the available and most popular brands of cling wrap available for the public and also used by major food outlets in South Africa.  The cling wrap will be extracted and tested for the presence of the following phthalates (DEHA, DEHP and DBP) and BPA using standard chromatography methods.  The estrogenic activity will be determined using the recombinant yeast estrogen screen (YES) and the T47D-KBluc reporter gene assay.  Human health risk assessment is the process or method of determining if an activity (man-made or natural) will negatively impact humans or their surrounding physical environment.  As such risk is a decision making tool.  This study will assess the carcinogenic and toxic human health risks posed by the chemicals found in cling wrap.  To ensure that the risk assessment is thorough and all conclusions are transparent, the assessment will follow the risk assessment methodology outlined by the United States Environmental Protection Agency (U.S. EPA 1989).

The information will identify cling film wraps that are free of EDCs and will guide CANSA to approve brands that are not only free of phthalates, but any of the other EDCs tested for that might pose a human health risk.

Non-scientific report

Eight cling wrap samples were frozen in liquid nitrogen andground to a fine powder. The powder was extracted in a Soxhlet apparatus using approximately 1g per sample per 100ml dichloromethane for 16 hours at 600C.  The dichloromethane extracts were then divided into two equal volumes, one of those volumes then dried under a stream of nitrogen and reconstituted in 5mL analyte grade acetone.  The samples were wrapped in foil and store at 40C.

Method development and validation of the LC-MS and the GC-MS and the retention times and mass for the target chemicals have been completed.  However, the method must be refined for the detection of BPA at 1 part per trillion (ppt) levels.  Once this is complete the cling wrap extracts will be analyzed.

UP-EDC laboratory received the extracts from Stellenbosch University in March 2012.  The extracts were tested in both the Yeast estrogen screen and T47D-KBluc bioassays.  However the following problems were encountered, dichloromethane is not a suitable solvent for the bioassays.  The extracts were then dried under nitrogen and reconstituted in HPLC grade ethanol.  The ethanol caused precipitation in certain of the clingwraps.  DMSO was then tried as an alternative solvent however the same occurred.  Currently the UP lab is doing a literature survey and also consulting an analytical chemist regarding the possibility of other alternative solvents suitable for the bioassays.  As soon as the laboratory has tested the other solvents and finds a suitable solvent the lab will proceed with the analyses.


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