The term pesticide covers a wide range of compounds including insecticides, fungicides, herbicides, rodenticides, molluscicides, nematicides, plant growth regulators and others. A pesticide can be a naturally derived or synthetically produced substance. A pesticide can also be an organism, for example, the bacterium Bacillus thuringiensis which is used to control a number of insect pests, or even a genetically modified crop. Insecticides are essential tools for controlling insect pests and therefore, improving the quality of life for humans, domestic animals and livestock. The uses of chemicals to protect crops is a vital activity. Without them, many crops would suffer dramatic losses. Some of these chemicals, the insecticides, are also very important in combating crop diseases. The environmental and toxicological properties of these chemicals have improved considerably over the last six decades. Because pests may develop resistance to crop protection chemicals there is a continual need for new products to be developed. Although pesticides have benefits, some also have drawbacks, such as potential toxicity to humans and other species. There are specific types of pesticides that are linked to specific health problems. Alachlor may cause eyes, kidney, liver and spleen problems. Atrazine can cause cardiovascular and reproductive problems. Endothall can cause stomach and intestinal problems. Effects from these chemicals may not show symptoms until years after your initial exposure. Pesticides are used to control organisms that are considered to be harmful. For example, they are used to kill mosquitoes that can transmit potentially deadly diseases like West Nile virus, yellow fever, and malaria. They can also kill bees, wasps or ants that can cause allergic reactions. Insecticides can protect animals from illnesses that can be caused by parasites such as fleas. Pesticides can prevent sickness in humans that could be caused by moldy food or diseased produce. Herbicides can be used to clear roadside weeds, trees and brush. They can also kill invasive weeds that may cause environmental damage. Herbicides are commonly applied in ponds and lakes to control algae and plants such as water grasses that can interfere with activities like swimming and fishing and cause the water to look or smell unpleasant. Uncontrolled pests such as termites and mold can damage structures such as houses. Pesticides are used in grocery stores and food storage facilities to manage rodents and insects that infest food such as grain.