These chemicals were detected in small quantities, but they are hard to break down so they tend to accumulate in nature to dangerous levels.

尽管这些化学物质被检测出的剂量少，但是因他们难以被分解而容易在自然界中聚集到足以产生威胁的水平。

youdao

Most parents didn’t have to deal with these issues when they were young and with technology advancing so fast it’s hard to stay on top of the threats, let alone understand them.

大部分的家长在孩子小的时候就没有正确处理这类问题。 而且在科技日新月异的今天，很难再危险发生之前就察觉出来。

youdao

Collected here are photos from the mountainous regions near Rio that were so hard-hit by these landslides.

以下图片来自里约热内卢附近深受山体滑坡打击的山区。

youdao

These warnings were not so much threats as statements of hard political fact.

ECONOMIST: Charlemagne

Now, certain investor groups are probably going to be vehemently opposed to this just because the way these things were structured and that goes to one of the reasons why it's been so hard to get everyone on board with something like this.

NPR: State of the Economy Check In

In these sceptical days, she explained, there was less demand for her rainmaking skills, so times were hard.

ECONOMIST: Queen Modjadji