Chemistry · Ch 16 — Green Chemistry and Nanochemistry
Design for Degradation
Design for Degradation
This principle asks chemists to design chemicals so that they degrade into harmless products and can be discarded easily once their useful life is over, and to ensure that both the original chemical and whatever it degrades into are not toxic, do not bioaccumulate (build up in living tissue), and do not persist indefinitely in the environment. The underlying aim is that waste products should be able to degrade on their own so that the environment is kept clean without needing further intervention -- which is why biodegradable polymers and biodegradable pesticides are always the preferred choice under this principle over their non-degradable equivalents. To help consumers separate different plastics for recycling, an international plastic recycling code -- a numbered triangle symbol -- is printed on larger plastic items, with the number identifying which of seven common plastic types the item is made from and therefore how it should be sorted and, where possible, recycled. A companion 'Do you know?' box adds a food-safety angle: phthalates can leach from plastic packaging into the food it hol …
Recycling code | Plastic | Typically used in | Health/reuse status | Recycled into
1 (PETE/PET, Polyethylene terephthalate) | microwavable food trays, salad dressing/soft drink/water/beer bottles | hard to clean, absorbs bacteria and flavours -- avoid reusing | carpet, furniture, new containers, polar fleece
2 (HDPE, High density polyethylene) | household cleaner and shampoo bottles | transmits no known chemicals into food | detergent bottles, fencing, floor tiles, pens
3 (V/PVC, Vinyl) | cooking oil bottles, clear food packaging, mouthwash bottles | believed to contain phthalates that interfere with hormonal development -- avoid | cables, mudflaps, panelling, roadway gutters
4 (LDPE, Low density polyethylene) | bread and shopping bags, carpet, clothing, furniture | transmits no known chemicals into food | envelopes, floor tiles, lumber, trash-can liners
5 (PP, Polypropylene) | ketchup bottles, medicine and syrup bottles, drinking straws | transmits no known chemicals into food | battery cables, brooms, ice scrapers, rakes …
Worked out. A caution box explaining that phthalates can leach out of plastic packaging into the food it holds, so the advice given is to avoid microwaving food or drinks in plastic containers, avoid plastic cling wrap, store food in glass containers wherever possible, and generally reduce exposure by avoiding pre-packaged, heavily processed food -- a practical, everyday extension of this section's recycling-code chart into food-safety advice. …