We are surrounded by the sounds of machinery that make our lives comfortable and convenient.

We are surrounded by the sounds of machinery that make our lives comfortable and convenient. The constant buzz of traffic and the thunder of jet engines overhead. But when we listen to these noises, often for too long or at the wrong time, they can inflict silent and stealthy damage. Increasing evidence shows this damage isn't just to our ears, but to our blood vessels and hearts. Nor is this just a problem for people who live near busy roads or under flight paths. New research suggests that noise pollution also causes damage in hospitals.

Last week, a study was published in Japan to discuss the silent findings about noise and health. Perhaps most eye-catching was the study that linked noise pollution to your waist size. In a four-year project, published last year, researchers from Karolinska University in Sweden found that the louder the traffic noise to which people in different parts of Stockholm were exposed, the greater their risk of obesity. The relationship was a centimetre increase for every ten decibel rise in the noise levels. That is, the ten-decibel rise corresponds to a centimetre increase in waistband circumference and a 20 percent increase in the risk of admission to hospital for heart disease by 20 percent. The effects of noise pollution are even felt by babies in the womb.

Last month, scientists from Karolinska University found an even more dramatic effect from plane noise. After tracking more than 5,000 people for ten years, they reported that the waistlines of those most exposed to plane noise increased on average by 6 cm. A similar study last year by the School of Public Health at Imperial College London found that being exposed to higher levels of aircraft noise increased the risk of admission to hospital for heart disease by 20 percent. The effects of noise pollution are even felt by babies in the womb.

What are the likely health effects of noise pollution?

• (I) It increases the risk of ear damage.
• (II) It increases the risk of blood pressure.
• (III) It increases the risk of obesity.
• (IV) It increases the risk of heart disease.