Toxicological Risks of Selected Flame-Retardant Chemicals (2000) / Chapter Skim
Currently Skimming:
9 Calcium and Zinc Molybdates
9 Calcium and Zinc Molybdates
Pages 192-228
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 192... ...
PHYSICAL AND CHEMICAL PROPERTIES The physical and chemical properties of calcium and zinc molybdates are presented in Table 9-1. OCCURRENCE AND USE Calcium and zinc molybdates are used as flame retardants in cellulosic materials and other polymers.
|
From page 193... ...
or zinc oxide (ZnO) is complexed with molybdenum trioxide (Mood.
|
From page 194... ...
TOXICOKINETICS Molybdenum Compounds There are no toxicokinetic data on Mo compounds following dermal exposure. Only limited data were located regarding the absorption, distnbution, metabolism, and excretion by humans of inhaled or ingested Mo compounds.
|
From page 195... ...
reported that zinc was present in human interstitial fluid (site of application) following dermal application of zinc oxide (dissolved in gum resin or hydrocolloids)
|
From page 196... ...
Distribution No relevant human or animal studies were located that investigated the distribution of zinc following dermal exposure to zinc compounds. No inhalation studies were identified that investigated the distribution of zinc in humans.
|
From page 197... ...
Following inhalation exposures, elevated levels of zinc were found in the urine of workers exposed to zinc oxide fumes containing unknown levels of Zn2+(Ham~i 1969, as cited in ATSDR 1994~. No other studies were identified that investigated the excretion of zinc following inhalation of zinc compounds.
|
From page 198... ...
Z nc There are two case studies in the scientific literature that suggest that occupational dermal exposure to zinc at high levels may cause or contribute to a skin condition referred to as "zinc oxide pox" which is described as itchy papular-pustular eruptions that occur in the pubic region, inner surface of the thigh, axilia, and inner surface of the arms.
|
From page 199... ...
Occlusive patch testing with zinc oxide, sulfate, pyrithione, or undecylenate produced little dermal irritation. Histological examination of skin samples from animals treated with zinc chloride or zinc acetate showed evidence of acanthosis, parakeratosis, hyperkeratosis, and inflammatory changes in the epidermis and in the more superficial aspects of the dermis.
|
From page 201... ...
describes the case of a fireman who died following exposure to a high but unknown concentration of a smoke mixture generated from a zinc chloride smoke bomb. Two soldiers developed severe respiratory distress syndrome and died 25-32 d following exposure to a high concentration of zinc chloride smoke mixture generated from a zinc chIoride smoke bomb (Hjortso et al.
|
From page 202... ...
1988~. The authors noted that the zinc oxide/hexachioroethane smoke contained a number of toxic chemicals including carbon tetrachIoride.
|
From page 203... ...
(1988) did not observe any abnormalities in the lymph nodes, thymus, or spleen tissue of female rats, mice, or guinea pigs killed at ~ ~ mo following a 20-wk exposure to zinc oxide/hexachloroethane smoke at concentrations as high as ~19.3 or 121.7 mg Zn2+/m3 for ~ hr/d, 5 d/wk.
|
From page 204... ...
The incidences of squamous metaplasia ofthe epithelium lining the base of the epiglottis were significantly increased in all exposed groups of mates and females. In both mate and female mice, the incidences of hyperplasia of the laryngeal epithelium at level TI of the larynx rose with increasing exposure concentration, but were statistically significant only in the highest dose group.
|
From page 205... ...
Serum Mo and serum xanthine oxidase levels were positively correlated with serum uric acid levels. Increasing urinary excretion of copper was positively correlated with increasing serum levels of Mo.
|
From page 206... ...
206 o o o .~ Cal .~ o EM Ct o au au ¢ o ~ ~= _' Cal Cal o Ct V, X^ o =^ ~ V: ~ 5-d Cq G ~ ~ To ~ At, ~ i O ~^ ~ o To So .
|
From page 207... ...
The high-Mo group consisted of ~3 college students from Golden, Colorado (Mo drinking water concentrations were greater than or equal to 200 ,ug/~. Urinary Mo and copper levels, and serum levels of ceruloplasmin and uric acid were compared between the two exposure groups.
|
From page 208... ...
These LDso values include 237,293,528, and 623 mg Zn/kg-d for rats and 86, 204, 605, and 390 mg Zn/kg-d for mice, following oral dosing with zinc acetate, zinc nitrate, zinc chloride, and zinc sulfate, respectively. Ingestion of zinc-containing compounds has resulted in a variety of gastrointestinal, hematological, and renal effects in humans and animals.
|
From page 209... ...
was ~ 2 mg Zn2+/kg-d as zinc chloride in a 4-wk drinking water study with 2-mo old rats. Malta et al.
|
From page 210... ...
No human studies identified renal effects following oral exposures to zinc compounds. However, several animal studies have demonstrated adverse renal effects in animals exposed to zinc oxide, zinc sulfate, and zinc acetate.
|
From page 211... ...
Very limited data were located on neurological effects in animals. Rats dosed with487 mg Zn2+/kg-d as zinc oxide for 10 d (Kozik et al.1980, as cited in ATSDR 1994)
|
From page 212... ...
reported that newborn and 14-d old rats, from mothers who had consumed 100 mg/kg-d throughout gestation, had elevated levels of total zinc and decreased levels of iron. Cancer Molybdenum Compounds No data were identified on carcinogenic effects of Mo compounds following oral exposure.
|
From page 213... ...
1992, as reported in NTP 19971. Molybdenum trioxide did not induce sister-chromatic exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells.
|
From page 214... ...
This study identified a LOAEL of 10 mg MoO3/m3 based on increased incidences of hyaline degeneration in the nasal respiratory epithelium and nasal olfactory epithelium in female rats. No NOAEL was identified in this study.
|
From page 215... ...
Since there are few other supporting data from inhalation studies examining similar effects, confidence in the database and in the inhalation RfC are medium.
|
From page 216... ...
In this epidemiological study, increases in uric acid levels and copper excretion, and elevated serum ceruloplasmin, were observed and a LOAEL of 0.14 mg/g-d Mo was identified. No NOAEL was identified in this study for Mo.
|
From page 217... ...
bRfD calculated based on percent by weight of molybdenum in calcium molybdates and zinc molybbates (43% and 48%, respectively)
|
From page 218... ...
Oral No studies were identified regarding the carcinogenicity of calcium or zinc molyb~ates or other Mo compounds following oral exposure in humans or experimental animals. Therefore, the subcommittee concluded that there are insufficient data to determine its carcinogencity.
|
From page 219... ...
1.8 6 5.4 8 17.7 15 EXPOSURE ASSESSMENT AND RISK CHARACTERIZATION Noncancer Dermal Exposure The assessment of noncancer risk for the dermal exposure route is based on the dermal exposure scenario described in Chapter 3. This exposure scenario assumes that an adult spends I/4th of his or her time sitting on furniture upholstery treated with calcium or zinc molyb~ates and also assumes 1/4th of the upper torso is in contact with the upholstery and clothing presents no barrier.
|
From page 220... ...
Therefore it was concluded that calcium and zinc molybdates used as flame retardants in upholstery fabric may pose a non-cancer risk by the dermal route at the specified concentration and under the given worst-case exposure scenario. Inhalation Exposure Particles Inhalation exposure estimates for calcium and zinc molybdates were caTculated using the exposure scenario described in Chapter 3 .
|
From page 221... ...
The subcommittee concluded that calcium or zinc molyb~ate used as an upholstery fabric flame retardant is not likely to pose any noncancer risk by the oral route. Cancer Dermal Exposure Based on inadequate data on the carcinogencity of calcium and zinc molybdates via the Berman route, the subcommittee concludes that there are insuff~cient data to assess its carcinogencity.
|
From page 222... ...
Oral Exposure Based on inadequate data on the carcinogencity of calcium and zinc molybdates via the oral route, the subcommittee concludes that there are insufficient data to assess its carcinogencity. RECOMMENDATIONS FROM OTlIER ORGANIZATIONS The OSHA permissible exposure limit (PEL)
|
From page 223... ...
1991. Release and absorption of zinc from zinc oxide and zinc sulfate in open wounds.
|
From page 224... ...
Available: ktt~://www epa.gov/ncisp~n3/iris/ Evans, E.H.1945. Casualties following exposure to zinc chloride smoke.
|
From page 225... ...
1999. Toxicity Review for Calcium Molybdate and Zinc Molybdate.
|
From page 226... ...
1980. Morphological and histochemical changes occurring in the brain of rats fed large doses of zinc oxide.
|
From page 227... ...
Metal-fume fever from inhaling zinc oxide.
|
From page 228... ...
An occupational dermatoconiosis among zinc oxide workers. Public Health Rep.36:2727-2732.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.