“Encapsulated lead chromate pigments do not release lead or chromium to the blood … Risks [normally] attributed to LEAD [toxicity] is dramatically reduce whenever encapsulated pigments are used.” Environment Toxicology and Chemistry, Vol 10, pp 1247-1253, 1991 – Silica Encapsulation Reduces Bio-availability – SETAC for copy
Stanley M Pier, Affiliate Associate Professor, School of Public Health, University of Washington, USA
Michael A Gallo & Thomas H Umbreit, Dept of Environmental and Community Medicine, University of Medicine and Dentistry of New Jersey, Rober Wood Johnson Medical School
Thomas H Connor, School of Public Health, The University of Texas Health Science Center, Houston, TX, USA
Donald Gray and Frank A Cappelleri, Cookson Pigments, Newark, New Jersey, USA
Recent years have witnessed a quantum jump in public concern over possible adverse health and environmental effects stemming from the extensive use of chemicals. concern exists in both occupational and community circumstances, with the community concern encompassing all possible media of exposure; ambient air, drinking water, food and recreational waters.
That many chemical substances are toxic cannot be denied. However, there has often been a failure to distinguish between toxicity and hazard.
Toxicity is an inherent property of a chemical, but in and of itself does not present a hazard, only a potential hazard (much like taking a small dose of aspirin can benefit you, while an overdose can kill you).
In the late 1960s, a unique process was developed whereby pigment particles such as lead chromate could be encapsulated with an amorphous silica coating. This was done primarily to achieve improved product performance characteristics, but also provides a basis for reducing the tocicity that would exist in the absence of the coating … resulting in the pigment particles [fusing together] to form an intact and stable shell.
The presence of an intact coating around the pigment particle offered the intriguing possibility that tissue contact would not occur and adverse impacts would be reduced or elminated…
Potential Leachate Toxcity
Lead chromate, both ordinary and encapsulated, was tested in the toxicity characteristic leaching procedure (TCLP) promulgated by the US Environmental Protection Agency. Both versions were also tested by the procedure employed in Europe designated DIN/ISO 6713, which required leaching with hydrochloric acid at 0.07 N. [ a highly caustic material used to test the point at which the encapsulation might begin to break down ] …
The data for a medium chrome yellow [pigment] [ed: encapsulated lead chromate] demonstrated the ability of the silica coating to resist attack by acidic agents, with the difference being most dramatic in the case of the lead moiety of the pigment.
Silica encapsulation of lead chromate pigments renders them nongenotoxic in in-vitro tests, even in the presence of a powerful chelating solubilizer [hydrochloric acid ], under conditions in which the identical pigment lacking encapsulation gives a positive mutagenicity test.
Encapsulated lead chromate pigments do not release lead or chromium to the blood … Risks [normally] attributed to LEAD [toxicity] is dramatically reduce whenever encapsulated pigments are used.
These findings have important [and positive] implications for health and environmental issues surrounding the use of encapsulated lead chromate [hexavalent chromate, yellow chrome pigment].
This finding indicates that sludge and waste generated from the use of encapsulated pigments may not require disposal as hazardous chemicals.
Refer to Silica Encapsulation Reduces BioAvailability [of Lead Chromate Pigments Used in Artificial Turf ] ; 1991 Environmental Toxicology and Chemistry, Vol 10 pp 1247-1253; Stanley M. Pier, School of Public Health, University of Washington; et al. – Order Copy From SECTAC Journals – View HERE
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