After several deliveries for an Olive Oil importer in the USA, it was found that the product had traces of a Naphthalene contamination. The source of the contamination was unknown but, given correct quality controls at the supplier side, it was clear that contamination was happening during transport.
Naphthalene is commonly used as a pesticide in shipping containers. Unfortunately, for some sensitive products such as edible oils, it can be a contaminant. However, shipping lines do not keep records of the pesticides used, and container regulations from country to country – making it very difficult to pin down.