A microbiologist has warned that even those who have recently purchased a new kitchen sink will still need to work hard to keep it clean and hygienic. Charles Gerba from the University of Arizona and health author Andrew Weil have come up with some handy tips on how to ensure your kitchen sink remains pristine.In a report published in Dr Weils online newsletter, the experts say that a kitchen sink can often be more contaminated than a toilet. They recommend that any sponges used on the sink are changed or sterilised on a regular basis which can be done through putting them in the microwave for five minutes or running them through the dishwasher. Smells coming from the kitchen sink can also be reduced, according to Dr Weil and Mr Gerba, who recommend that half a cup of baking soda and half a cup of vinegar is poured down the drain with hot water to cleanse it.