While every plant, animal, and insect has a place in the grand scheme of things, not everything has a place in the grand scheme of your landscaping plan or cottage vacation. When weeds, mosquitoes, and mice invade your sanctuary, it can be tempting to turn to chemical pesticides to get rid of them. However, the environmental impact of this decision can be high, so make sure you're properly informed before you go ahead and spray.
The first thing you need to realize is that although the product packaging may advertise a targeted attack on the pest of your choice, there is at least a 95% chance that any chemical you spray will end up affecting other things too. They can seep into the ground and end up in the water where they might kill fish or drift on the wind to cause problems in neighboring farms or fields or even kill the bees which are responsible for the health of your beautiful flowers. Learn more about the various water solutions used to clean water for safe use.
Humans too, can suffer ill effects from your decision to apply pesticides. The water treatment chemicals you use can make their way into human tissue through air pollution, soil contamination, and water pollution, causing rashes, nausea, headaches, asthma, heart disease, birth defects, and even cancer. This is especially true for children, who are more vulnerable and get higher exposures from being closer to the ground. Any pets in the area will also suffer ill effects if exposed to pesticides. Some pesticides, such as DDT, don't even break down and will stay in the soil for years.
Some municipalities have already placed bans on the use of certain types of pesticide, such as DDT and pentachlorophenol, so be sure to check with your local authorities before you go ahead and use any sort of pesticide. You may even want to take some aquarium test kits and determine if your property is already cross contaminated, which can lead to pesticide resistant weeds and insects who may not even respond to your use of chemicals on them.
A greener alternative to chemicals is available. You can use chili pepper, wormwood, garlic, and soap to get rid of many yard based pests. If you must use chemicals, however, apply a high temperature curtain approach to prevent cross contamination by leaving a broad land buffer or wind break of trees between the sprayed area and your neighbors' properties. You should also ground spray rather than air spray to prevent drift.