Googled it and it is not safe. The very items you suggest as 'safe' are labeled as unsafe.
"The burning of polystyrene polymers - such as foam cups, meat trays, egg containers, yogurt and deli containers - releases styrene. Styrene gas can readily be absorbed through the skin and lungs. At high levels styrene vapor can damage the eyes and mucous membranes. Long term exposure to styrene can affect the central nervous system, causing headaches, fatigue, weakness, and depression. Not only these people who are burning the trash are exposed to these pollutants, but also their neighbours, children and families.
https://www.wecf.eu/cms/download/2004-2005/homeburning_plastics.pdf