The answer is competition for jobs. The Chinese would do a lot of work for very little pay, most Americans couldn't keep up and were losing their jobs to these Chinese immigrants.
It was the Love Canal tragedy that significantly impacted the passage of the Superfund Act in 1981, since prior to this there was no collectivized way to go about cleaning up these kinds of disasters at a federal level.
The event led to a rapid population increase in California in the late 1840s is the discovery of Gold in California. Due to the discovery of Gold a lot of people like miners and traders settle in California and thus starting the Gold Rush in late 1840s. Also due to the Gold Rush in California a large number of foreigners and people around the globe flocked in California for gold.
