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Another example of a natural contaminant is plant root penetration on wood, charcoal, or soil.
Artificial contamination refers to the introduction of contaminants by man during the collection, field conservation, or packaging of the samples.
Labeling of bone samples with animal glue is an example of artificial contamination.
Other contaminants that may be introduced during sample collection and packaging are biocides, conservation chemicals like polyvinyl acetate and polyethylene glycol, cigarette ash, and labels and wrappers that are made of paper.
For example, bone samples can be contaminated by the presence of limestone or organic acids in the soil (like humic or fulvic acids) where the bones were found.In general, infinite-age contamination can make a sample considerably older while modern contamination can make the sample significantly younger than its true age.