可以用 "the environment is deteriorating" 来表达环境变得越来越差的意思。
"Deteriorate" 是英文中的一个动词，意思是变坏、恶化。在这里指的是环境变得越来越差。
举几个例子：
The air quapty in the city has been deteriorating for years. (城市的空气质量已经多年恶化了。)
The forest is slowly deteriorating due to logging and deforestation. (森林因伐木和清洁而慢慢恶化。)
The water in the lake is deteriorating because of pollution. (湖里的水因污染而恶化。)