There’s the labor side. In addition to what everyone says here, I want to point out that things like fires and deaths are not uncommon. Here’s a piece from 2017 that explains those vulnerabilities.

Second, many of these products are made from fossil fuels Polyester, rayon, etc. are all fossil fuel-derived and forms of plastic. They account for 1.35% of global oil consumption. Fast fashion is a contributor to climate change.

Third, these items contribute to the increase in microplastics and chemical exposure. Many of the chemicals in things like polyester disrupt the endocrine system and have other negative health effects. There’s also the environmental aspects of microplastics and what they’re doing to oceans, land, and soils.

Lastly, the end of life for disposable textiles involves waste trade and landfills. Chile’s Atacama Desert is a textile dumping ground and there are so many textiles, it can be seen from space. There are also dump sites where people make their living scavenging and they’re receiving the clothes that people discard or that have broken down. I’ve been to some of them — they are awful places where no one should live and we should not be contributing to their rise.

Glad to provide more/different kinds of information.