Ask the experts: Dishwashing liquid and cancer

Q: "My husband does a lot of the washing up in our house but believes that dish washing liquid can cause cancer or illness, so he washes everything under a running tap, using a sponge with detergent and rinsing off all the soap suds and residue. Unfortunately this method uses a lot of water. What is the evidence around the safety (or not) of dishwashing liquids?"

A: Caroline Gunn, director of Food Safety Services Ltd in Napier, responds:

 "There is approximately 8.6 million kilograms of hand dishwashing detergent consumed every year in NZ. There is increasing concern that some cleaning products can be detrimental to both health and the environment because of some of their ingredients and the continuous and diverse use of these products.

A typical hand dishwashing detergent contains ingredients for cleaning, foaming and substances that allow the detergent to dissolve quickly in water. Other ingredients are associated with preservation, colour, fragrance and anti-irritation. By far the major active component in hand dishwashing detergent is surfactant, which is the main cleaning ingredient for cutting through grease as well as forming suds or foams. Most surfactants are anionic and are used in conjunction with lauric, myristic and ethanol amides and hydrotopes (the dissolvers) such as propylene glycol and polyethylene glycol ethers. Some of these chemicals (in some detergents) may possibly be harmful if there is exposure on a continuous and long-term basis, but there is a lack of long-term studies to verify this. As a result many people (including your husband ) are taking the cautious approach.

The best advice, if you are concerned about the long-term effects of these products to either your health and/or the environment, is to go for eco-friendly products which have been licensed to use the label 'Environmental Choice NZ'. This is a NZ government initiative which aims to manage the formulation of hand dishwashing detergents so no known carcinogenic, mutagenic or toxigenic substance is included in the product. Another key aim is to improve their environmental impact. The label 'Environmental Choice NZ' provides you with the assurance that the product complies with their requirements.

To view the list of formulation requirements and which chemicals are not allowed in the detergent, visit the  website at www.enviro-choice.org.nz."