51.   Environmental factors and human activities are responsible for the poor health of coral reefs and the marine ecosystems they support, Yozell said.

52.   Environmental factors play large roles in newer histories of the West.

53.   For one thing, these are multiple gene traits heavily influenced by environmental factors.

54.   For some people, treatment of dry eye may be as simple as changing medications or reducing exposure to environmental factors.

55.   Genetic factors often are involved and environmental factors, such as vaccinations, are being investigated.

56.   He searches for genes that may, with environmental factors, make people vulnerable to mental disorders like schizophrenia and manic-depressive illness.

57.   Health care providers throughout Texas are being asked to track chronic diseases under a new program aimed at exploring possible links between illness and environmental factors.

58.   In addition, even after the most violent incidents investigators are generally able to obtain blood samples, and the blood is generally not heavily contaminated by environmental factors.

59.   In any case, many researchers think genes govern only a susceptibility to myopia, which some environmental factor must trigger.

60.   In the body, the effects of either or both of these mechanisms can be modified by such environmental factors as exposure to ultraviolet light.