| FLUORIDE | Anion added to water supplies to reduce the incidence of tooth decay in the population (8) |
| NITRATE | Chemical affecting the incidence of lice? (7) |
| TARTAR | A cause of tooth decay in rodents returned (6) |
| RESIDENT | One counted in the population |
| PERCAPITA | For each person in the population (3,6) |
| THEDAM | Those responsible for WWII "bouncing bomb" raid on water supplies to factories in the Ruhr Valley became known as ... Busters (3,3) |
| MAINS | Electricity, gas, water supplies to house (5) |
| EPIDEMIOLOGY | Study of the incidence and distribution of diseases |
| EPIDEMIOLOGIST | Person who studies the incidence and distribution of disease (14) |
| MARSHGAS | Mixture primarily of methane and other compounds formed when organic material decays in the absence of air (5,3) |
| POLYGAMY | College with sensational high incidence of unions? (8) |
| SCARIEST | Most worrying tooth decay, in a way (8) |
| CANARIES | Article stopping tooth decay in birds (8) |
| AIRDROPS | Gets supplies to troops, in a way |
| OUTBREAK | Sudden incidence (8) |
| ISOPLETH | Line on map connecting points having equal meteorological incidence (8) |
| SOHO | John Snow's study of an outbreak of cholera in this London West End area led to the discovery that water supplies were the means of spreading this disease |
| SNELLSLAW | Formula relating to the angles of incidence and refraction, used in the field of optics (6,3) |
| ANTIFREEZE | Liquid, usually ethylene glycol, added to water in an internalcombustion engine in cold weather (10) |
| LEND | An act, signed by Roosevelt in 1941, authorised war supplies to the Allies on the basis of ... or le |
