Diethyl phthalate (DEP) is a plasticiser widely used in everyday personal care products (pcp) such as toothbrushes, perfumes, lotions, cosmetics, hairspray, nail polish, soaps and detergents. It is therefore easily exposed to the human population and can cause adverse health effects.

Humans are exposed to DEP primarily by dermal absorption, for which physiological toxicokinetic models involving PCPs and human dermal exposure to DEP have been developed for use in assessing health risks. The dermal absorption fraction of DEP was obtained to be 56.2% for PCPs exposure and 100% for air-to-skin exposure, respectively. Approximate 24.9% of DEP in exposed skin became absorbed into systemic circulation. Model predictions were generally within 2-fold of the observed MEP levels in human serum or urine. Uncertainty analysis showed 90% of the predicted variability (P95/P5) fell within less than one order of magnitude. Assuming human intake of 5 mg/kg bw per day, the predicted serum area under the curve at steady state of DEP from the dermal route was 1.7 (PCPs) and 2.4 (air) times of those from the peroral route, respectively. It suggested that dermal exposure to DEP would pose greater risk to human health compared with oral exposure.

Diethyl phthalate is irritating to the skin, eyes, nose and throat on short-term exposure or by inhalation, and can cause headache, dizziness and nausea, numbness, pins and needles, or weakness in the hands and feet when ingested. In addition, animal toxicity studies have shown that certain phthalates also affect male reproductive development by inhibiting the biosynthesis of androgens, which may lead to foetal malformations.DEP exposure may also lead to impaired cardiovascular electrical health, and induce a hormonal response after prolonged exposure.