<span>Exposure to cigarette smoke mostly is the case</span>
Depending on what water source you use, if your using faucet water your food will be clean but not totally.
If your using a lake, ocean, bodies of water your food will not be as clean, water from bodies of water are full of bacteria, and other contaminants.That being said, using a faucet is your best bet or even try to clarify water from bodies can help.
Answer:
Work with agricultural scientists in plant, fiber, and animal research, or assist with animal breeding and nutrition. Set up or maintain laboratory equipment and collect samples from crops or animals. Prepare specimens or record data to assist scientists in biology or related life science experiments.