Lead chromate, toxicity

The most common toxic metals in industrial use are cadmium, chromium, lead, silver, and mercury less commonly used are arsenic, selenium (both metalloids), and barium. Cadmium, a metal commonly used in alloys and myriads of other industrial uses, is fairly mobile in the environment and is responsible for many maladies including renal failure and a degenerative bone disease called "ITA ITA" disease. Chromium, most often found in plating wastes, is also environmentally mobile and is most toxic in the Cr valence state. Lead has been historically used as a component of an antiknock compound in gasoline and, along with chromium (as lead chromate), in paint and pigments. 

Preparations containing >0,5% lead chromate are required to be labelled according to EU Guideline 67/548/EEC (Annex I) as toxic (Symbol skull and crossbones) and beside others with the Risk phrases R 40 (limited evidence of carcinogenic effect), R 61 (may cause harm to the unborn child) and R 62 (possible risk of impaired fertility). 

Lead chromate is almost insoluble and has very low bioavailability. Studies on lead chromate pigment have shown that it does not have the carcinogenic potential of soluble chromates, such as zinc chromate. As with other heavy metals, solubility is the key to toxicity. With proper safeguards such as adequate ventilation and personal protective equipment, chrome yellow and molybdenum orange can be safely used in the workplace. 

The EPA regulates both lead and hexavalent chromium in its hazardous waste regulation. Solid waste containing lead chromate or lead molybdate should be tested for toxicity prior to disposal via the TCLP test. 

While the use of sugar of lead as a sweetener died out after the fall of the Roman Empire, the use of lead salts in food did not. Much more recently, for example, lead chromate, or chrome yellow , has been used to colour sweets and custard powder. As recently as the nineteenth century toxic metal salts were used as food colourants, for example the dye Scheele s green was used to colour blancmanges green. This dye is copper arsenite, containing both copper and, more importantly, arsenic. 

Lead chromate and lead chromate pigments are classified as toxic for reproduction (Unborn child Rep. Cat. 1/category Re 1, fertility Rep. Cat 3/category Rp 3) and carcinogenic (Care. Cat 3/category C 3 [3.135, 3.138]. 

In the EC lead chromate and lead chromate pigments must be appropriately labeled. Such substances must carry the symbols and indications of danger T, Toxic (skull and... 

For road transport in accordance with GGVSE [3.150] and ADR 2003 [3.151], lead chromate pigments and lead chromate containing preparations are assigned to class 6.1 (T5), III (UN-No. 2291) and have to be labeled with hazard symbol 6.1 (Toxic), if the lead content soluble in hydrochloric acid ]c(HGI) = 0.07 mol L ] exceeds 5%. 

All compounds of chromium are colored the most important are the chromates of sodium and potassium and the dichromates and the potassium and ammonium chrome sulfates. The dichromates are used as oxidizing agents in quantitative analysis, and also in tanning leather. Other compounds are of industrial value lead chromate is chrome-yellow, a valued pigment. Chromium compounds are used in the textile industry as mordants (substances capable of binding dyes to textile fibers), and by the aircraft and other industries for anodizing aluminum. Chromium compounds are toxic and should be handled with proper safeguards. 

Lead chromate (chrome yellow [CAS 7758-97-6]) Toxicity may result from both the chromium and the lead compohehts. Lead chromate is a suspect human carcinogen owing to the carcihogehicity of hexavalent chromium and inorganic lead compounds. See both lead and hexavalent chromium, pp 238 and 167. 0.05 mg/m (as Pb) 0.012 mg/m (as Cr), A2 Yellow pigment in powder or crystal form. 

Chromium is a human element . There is a trace amount (1-12 mg) in the body, which is needed to utilise glucose, and it is also involved in an unknown type of interaction with RNA. Lack of chromium can lead to diabetes, however, high concentrations, especially of chromates, are labelled as extremely toxic (and are suspected as being carcinogenic). Chromium workers usually develop chrome ulcer disease. Compounds containing hexavalent chrome are considered serious human health hazards. OSHA, NIOSH, and CDC determined that calcium chromate, chromium trioxide, lead chromate, strontium chromate and zinc chromate specifically cause (lung) cancer [43]. 

The main use for lead today is in solder, bullets (it is one of the heaviest stable elements), and car (lead-acid) batteries. Because it s so malleable and soft, yet not prone to rusting (oxidation), it was thought to be excellent for piping until its toxicity was understood. Lead can still be found in some paints because it creates certain colors such as chrome yellow (lead chromate), white (lead sulfate), and red (lead tetroxide). Lead was also widely used as an additive to automotive fuel in the form of tetra-ethyllead, but it is not as common anymore. 

Yellow and orange Cadmium sulfide produces orange-yeUow or similar shades when combined with zinc or selenium, but it contains the problematic heavy metal and is mainly used in engineering applications. Lead chromate produces bright yellows, but is light-sensitive and must be treated. Lead chromate, sulfite, and molybdate combined can create a stable orange color. Newer non-toxic compounds based on rare earth elements, such as cerium sulfide, reportedly offer the same shades as toxic chromates. 

Toxicology ACGIH TLV/TWA 5 mg/m TDLo (implant, rat) 3760 mg/kg toxic by inh. may cause skin injury questionable carcinogen experimental tumorigen TSCA listed Precaution Dust or powd. may be flamm. dry powd. ignites spontaneously in air incompat. with bromine trifluoride, fluorine, lead chromate attacked by HF, fused alkalis, fuming H2SO4... 

Lead chromate has been used as a pigment, although both the lead ion and the chromate ion are toxic. What is the molar solubility of PbCr04 in water ... 

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