Unintentional seeding

Unintentional seeding may also occur even if small amounts of the undesired polymorph are present as contaminants—in fact, in principle just one such seed is... 

The deliberate use of seed crystals is common practice in both research laboratory, e.g., to encourage the crystallization of a difficult substance, and in industrial plant to exert control over the crystal size distribution of the final product (section 8.4.5). On the other hand, unintentional seeding, also frequently encountered in both laboratory and industry, is an uncontrolled event which can often cause considerable frustration and trouble. 

Undoubtedly, many of the above and other examples have been caused by unintentional seeding. Reference has already been made in section 5.1.2 to the role atmospheric dust can play as a nucleating agent, noting that even foreign bodies in the dust can also act as nucleation promoters. Once a certain crystalline form has been prepared in a laboratory or plant, the working atmosphere inevitably becomes contaminated with seeds of the particular material. If later a thermodynamically more stable polymorph or hydrate (pseudopolymorph) appears, then seeds of this too will enter the atmosphere and play a dominant role. However, it is the speed with which another laboratory or plant, often some large distance apart, sometimes even in another country, also become... 

Thus, on the basis of quantity and size required to play a role, once a crystal form exists in a certain locale the presence of seeds is almost always possible, indeed often unavoidable. One can think of local seeding, where the unintentional source may come from e.g. the experimentalists clothing, a portion of the room, an entire room, a building, or even, with increasing degrees of improbability, increasingly larger environments. ... 

More recently, certain non-natural, exogenous contaminants in fats and vegetable oils have become an issue (43). Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dioxins, and aflatoxin, to name the more serious offenders, can hnd their way into fats and oils by a variety of pathways. In the case of PAHs, direct drying of seed materials (44, 45) is a major pathway. Dioxins, released to the environment as unintentional byproducts of combustion processes, are mainly found in animal and hsh fats as a result of ingestion of dioxin-contaminated feeds, soils, and sediments (46) by these animals. PCBs were used as dielectric fluids in electrical equipment and as flame-retardants until their production was banned (USA—1977 Europe—1985) they are generally not found in edible oils. 

Poisoning may occur through ingestion, drinking tea, or smoking the plant. Seeds have the highest concentration of toxin. Exposure may be unintentional or for experimentation purposes due to the hallucinogenic properties of the plant. 

Poisoning may occur through ingestion. Unintentional ingestion can occur from coniine when similar plants are mistaken for parsley, anise (seeds), or carrot plant. It is tuberous, similar to turnip roots. 

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