养老金支出水平是不可持续的。

The level of spending on pensions is ___unsustainable.

当前的经济增长模式长期来看是不可持续的。

Current economic growth models are ___unsustainable in the long term.

如此高的污染水平对我们的星球来说是不可持续的。

Such high levels of pollution are ___unsustainable for our planet.