What does a PECQ value of greater than 1 suggest?

A PECQ value greater than 1 indicates that the concentration of a substance in the environment is higher than the concentration known to cause adverse effects on aquatic life. This suggests that the substance may pose a significant risk to the ecosystem and could potentially lead to harmful outcomes for aquatic organisms. In environmental assessments, such values trigger concern and necessitate further investigation into the substance's effects, as they suggest a likelihood of negative impacts on biodiversity and ecosystem health.

The other choices present misunderstandings of how PECQs are assessed and interpreted. A value greater than 1 does not imply the substance is harmless, nor does it suggest that the substance is not relevant for environmental evaluation. Likewise, it cannot be safely applied in natural habitats since the evidence points towards potential ecological harm.