Answer:
<em>Coal ash contains toxic levels of several different pollutants, so when it is collected and stored long-term in coal ash ponds, there is increased
</em>
<em>risk of exposure to toxic metals.</em>
Explanation:
The option above best describes an environmental disadvantage of using industrial scrubbers and electrostatic precipitators for pollution abatement.
The answer would be or because the sentence it gives two different choices in the sentence.