The various forms of crystalline silica are: α-quartz, β-quartz, α-tridymite, β-tridymite, α-cristobalite, β-cristobalite, keatite, coesite, stishovite, and moganite. NIOSH (2002)....Keatite, coesite, stishovite, and moganite are rarely found in nature. The most commonly occurring polymorphs are quartz, cristobalite and tridymite, which are found in rocks and soil. 

NIOSH Hazard Review: Health Effects of Occupational Exposure to Respirable Crystalline Silica (DHHS (NIOSH) Publication No. 2002–129). Cincinnati, OH, 145 pp.

From https://www.ncbi.nlm.nih.gov/books/NBK304370/#

This compound group includes both commercially relevant compounds such as Hydrogen Cyanide, Sodium Cyanide, Potassium Cyanide, and Calcium Cyanide, as well as cyanide salts that are less common. 

This group hasn't been assigned a structural definition yet.

This group hasn't been assigned a structural definition yet.

This group hasn't been assigned a structural definition yet.

This group is populated from the list at https://biomonitoring.ca.gov/chemicals

This compound group is defined by the SMILES string 'C1CCC2C(C1)C(=O)OC2=O'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This compound group is defined by the SMILES string 'C=[N+]=[N-]'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This group has not been assigned a structural definition yet.

This compound group is defined by the SMILES string 'CCCC[Sn]CCCC.CCCC[Sn]CCCC'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This group is populated from the list at https://biomonitoring.ca.gov/chemicals

This compound group is from the C2C V4 RSL.

This compound group was populated using a list of chemicals that are reportable under the MA Toxics Use Reduction Act (TURA). See https://www.mass.gov/guides/massdep-toxics-use-reduction-program#-listed-chemicals- for more information.

This compound group has not yet been assigned a structural definition.

This compound group is defined by the SMILES string '[CH3][As](=O)([CH3])O'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This compound group is defined by the SMILES string '[CH3][Sn]([CH3])', then subtracting compounds with 3+ methyl ligands. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This compound group is defined by the SMILES string '[CH3]C1=[CH]C(=[CH]C(=C1[OH])[N+](=O)[O-])[N+](=O)[O-]'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This compound group is defined by the SMILES string 'CCC(C)C1=CC(=CC(=C1O)[N+](=O)[O-])[N+](=O)[O-]'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This compound group is defined by the SMILES string 'CC(C)(C)C1=CC(=CC(=C1O)[N+](=O)[O-])[N+](=O)[O-]'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This compound group is defined by the SMILES string 'CCCCCCCC[Sn]CCCCCCCC'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This compound group has not been populated yet.

This compound group was populated using a list of chemicals that are reportable under the MA Toxics Use Reduction Act (TURA). See https://www.mass.gov/guides/massdep-toxics-use-reduction-program#-listed-chemicals- for more information.

This compound group has not yet been assigned a structural definition.

This compound group is defined by the SMILES string '[CH]1=[CH][CH]=C([CH]=[CH]1)[Sn](C2=[CH][CH]=[CH][CH]=[CH]2)'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This compound group is defined by the SMARTS string 'C(=[SD1])([ND1])[SD1]'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

Populated from Swedish EPA

http://webapps.kemi.se/flodesanalyser/

This compound group has not yet been assigned a structural definition.

This compound group has not yet been assigned a structural definition.

This group has not been assigned a structural definition yet.

This compound group is defined by the SMILES string 'C(CN)N'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This compound group has not yet been assigned a structural definition.

This compound group is populated by its subgroups and literature searches for flame retardants. Please contact support@pharosproject.net with any suggestions or additions.

This group includes minerals, amines, and inorganic phosphates

This compound group has not yet been assigned a structural definition.

This compound group has not yet been assigned a structural definition.

This group was populated from the OECD's Comprehensive Global Database of Per- and Polyfluoroalkyl Substances (PFASs) at http://www.oecd.org/chemicalsafety/portal-perfluorinated-chemicals/.

This compound group has not yet been assigned a structural definition.

This compound group is populated by taking the more general compound group and subtracting the chemicals found in the relevent Annex.

This group was populated from the OECD's Comprehensive Global Database of Per- and Polyfluoroalkyl Substances (PFASs) at http://www.oecd.org/chemicalsafety/portal-perfluorinated-chemicals/.

This compound group was populated by searching ChemIDplus for all compounds whose name contained "formaldehyde". Additionally, it contains the compounds in its subgroups. 

This compound group was populated with chemicals in Pharos with both "urea" and "formaldehyde" in the name.

This compound group is populated from a list of chemicals in an ECHA Investigation Report - Formaldehyde and Formaldehyde Releasers as well as manual searches. Report downloaded from https://echa.europa.eu/documents/10162/13641/annex_xv_report_formaldehyde_en.pdf/58be2f0a-7ca7-264d-a594-da5051a1c74b

149-44-0 (Sodium formaldehyde sulfoxylate) was added based on suggestion by GreenSeal, citing https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-hydroxymethanesulfinate and https://www.fishersci.com/store/msds?partNumber=AC149190250&productDescription=SODIUM+FORMALDEHYDESULFO+25KG&vendorId=VN00032119&countryCode=US&language=en 

This compound group is defined by the SMILES string 'C1=COC=C1'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This compound group is defined by the SMILES string '[Ge]'. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.

This compound group has not yet been assigned a structural definition.

The SMILES string "COCC1CO1" captures all glycidyl ethers but is not specific enough as the only filter. For more information on SMILES, see https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system.