While plastic containers and water bottles may seem convenient and easy to carry, you should avoid using them as much as possible. According to research, plastics are harmful to health and using them may lead to infertility and cancer. Heating food in plastic containers leads to 'migration' which means trace amounts of plastic leeches into your food. Plastic contains phthalates; this chemical disturbs the endocrine-system and promotes obesity. Plastic grocery bags should also be avoided as they are not airtight and pests can get in easily.