Sawdust from pressure treated wood contains __________ and should not be used as an organic additive.

The correct answer highlights that sawdust from pressure-treated wood contains toxic residues, which can pose significant risks when used in gardening or horticulture. Pressure-treated wood is treated with chemicals, including arsenic or other preservatives, to protect it from decay and pests. These substances can leach into the soil and potentially harm plants, animals, and humans.

Using material that contains toxic residues as an organic additive compromises the health of the soil and the plants growing in it. It can lead to contamination and adverse health effects over time, especially if crops intended for human consumption are grown in such soil. Therefore, it is important to avoid using sawdust or any wood products treated with harmful chemicals to maintain a safe and healthy gardening environment.

The other options do not accurately reflect the concerns associated with using pressure-treated wood. For instance, while non-toxic minerals may be beneficial in some contexts, they do not apply here due to the presence of harmful substances. Similarly, the concept of fertile nutrients or organic matter does not pertain since the additives in question are compromised by the toxic nature of the wood treatment.