41.   U.N. officials warn vibrations and car exhaust will further erode the pyramids and their neighbor, the Sphinx.

42.   UNESCO said the treasures, already eroded by weather and pollution, would be further damaged by car exhaust, ground vibrations and urban sprawl.

43.   Greenhouse gases are mainly carbon-based substances, such as carbon dioxide, that are emitted by car exhausts, power stations and factories.

44.   A car exhaust backfiring set off panic during a meeting between senior Israeli army officials and the Palestinian police chief in Jericho on Monday, witnesses said.

45.   Air quality in Guangzhou has seriously deteriorated over the past two decades and the city is usually blanketed by car exhaust.

46.   But the gas acts as an irritatant when it forms on the ground, notably from chemicals from car exhausts reacting with sunlight.

47.   Carbon monoxide is a colourless, odourless and tasteless gas, also present in car exhausts, that causes suffocation.

48.   They were analysed with a technique developed to distinguish between lead from car exhausts and from soil minerals.

49.   On Sunday, the alert was posted again in northern areas where smog caused mostly by car exhaust blanketed the sky.