Final answer:
Individuals are limited to purchasing up to 3.6 grams of ephedrine or pseudoephedrine per day and no more than 9 grams in 30 days, as these substances can be converted into methamphetamines; identification and logs of purchases are also required.
Step-by-step explanation:
The purchase limits for ephedrine and pseudoephedrine, two active ingredients commonly found in cold medications and used for their decongestant properties, are regulated due to their potential for being converted into methamphetamines. In the United States, the Combat Methamphetamine Epidemic Act of 2005 has set legal restrictions. Individuals are allowed to purchase up to 3.6 grams of ephedrine or pseudoephedrine bases per day, and no more than 9 grams in a 30-day period from retail establishments. It's also required that purchases are logged and personal identification is provided to track the sale of these substances due to their association with the illicit production of methamphetamines.