Toxic particulates

No adverse health effects were observed in male rats exposed by inhalation to 3,3 -dichlorobenzidine free base (23,700 mg/m ) 2 hours per day for 7 days (Gerarde and Gerarde 1974). In another study, 10 rats were exposed to an unspecified concentration of 3,3 -dichlorobenzidine dihydrochloride dust particles for 1 hour and then observed for 14 days. Slight-to-moderate pulmonary congestion and one pulmonary abscess were observed upon necropsy (Gerarde and Gerarde 1974). The effects observed in the study using the ionized (hydroehloride) form of 3,3 -dichlorobenzidine may have been due to the irritative properties of hydrochlorie aeid released from the salt in combination with particulate toxicity. 

While it is possible that these symptoms were due to exposure to 3,3 -dichlorobenzidine hydrochloride, the irritant effects of HCl from the compoimd in combination with particulate toxicity could have been responsible for the observed effects in these studies. Therefore, it is not likely that respiratory ailments will occur in humans exposed to 3,3 -dichlorobenzidine at hazardous waste sites. 

Cytotoxicity assays employ mammalian celk in culture to measure cellular metabolic impairment and death resulting from exposure in vitro to soluble and particulate toxicants. Mammalian cells derived from various tissues and organs can be maintained as short term primary cultures or, in some cases, as continuous cell strains or lines. The cytotoxicity assays, incorporated as part of Level 1 analysis, employ primary cultures of rabbit alveolar (lung) macrophages (RAM) and maintenance cultures of strain WI-38 human lung fibroblasts. 

In applying the PEEP index concept to sets of industrial effluents thus far, wastewater samples have been filtered prior to bio-analysis (see Section 5.1). Hence, only their soluble toxicity potential is taken into consideration. This is certainly a drawback at this time as toxic and genotoxic potential linked to suspended matter of some industrial plant effluents, for example, have been shown to be important (White et ah, 1996 Pardos and Blaise, 1999). Particulate toxicity in effluent samples should certainly be addressed in future PEEP applications, as soon as reliable small-scale toxicity tests are developed and available to estimate it. Indeed, the issue of soluble and particulate toxicity is especially relevant in relation to technology-based reduction of hazardous liquid emissions. 

Although this chapter focuses on applications with effluent wastewaters, all types of aquatic environmental media (freshwater, brackish, marine) can be appraised with the pT-scale procedure. Testing of liquid samples is virtually unlimited and can include untreated and treated wastewater, surface water, ground water, porewater, elutriates and organic extracts of sediments. Applications could also be extended to assess toxicity of particle-bound substances in suspended matter and sediments. In this case, sample dilutions can be made with reference sediment material (Hoss and Krebs, 2003). The pT-method can also capture the effects of both soluble and particulate toxicity in a sample, provided that appropriate bioassays are employed. 

TABLE 4.64 Examples of Occupational Exposure to Particulate Toxic Agents... 

Which mechanism is most esservtial to clearing particulate toxicants from the tracheobronchial tree ... 

Miller FJ, Anjilvel S, Menache M, Asgharian B, Gerrity TR. Dosimetric issues relating to particulate toxicity. Inhal Toxicol 1995 7 615-632. 

Costa DL, Lehmann JR, Frazier LT, et al. Pulmonary hypertension a possible risk factor in particulate toxicity. Am J Respir Crit Care Med 1994 149 A840. 

Kurthermore, the open exposure of mercury in iny apparatus, particul.arly one an frequent use, is to be avoided, as even at room temperature the mercury eives annreciable uuantitv of the toxic vanour. 

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

Methanol use would also reduce pubHc exposure to toxic hydrocarbons associated with gasoline and diesel fuel, including ben2ene, 1,3-butadiene, diesel particulates, and polynuclear aromatic hydrocarbons. Although pubHc formaldehyde exposures might increase from methanol use in garages and tunnels, methanol use is expected to reduce overall pubHc exposure to toxic air contaminants. 

The toxicity of a metal in powder form may vary from that of the massive metals in that fine particles can be ingested or inhaled more readily (41). The metal powder producing or consuming industries must conform to OSHA requirements. The limits of airborne particulates are set by NIOSH. 

The solubiHty of phosphoms in water is about 3 ppm. However, process water used in phosphoms manufacture or handling often catties larger amounts of phosphoms as particulates or small droplets, depending on the water temperature. Phosphoms-contaminated water is commonly called phossy water. Phosphoms has low solubiHty in most common solvents, but is quite soluble in carbon disulfide and some other special solvents. The solubiHty in CS2 and benzene was formerly used in phosphoms analyses, but toxicity and increasing waste disposal costs have led to mote use of toluene and xylene, and mote tecentiy to the use of nonchemical turbidity measurements. 

The monoalkyl derivatives in salt form appear to have low toxicity. The monomethyl sulfate sodium salt has an approximate oral lethal dose greater than 5000 mg/kg of body weight for rats (129). Monododecyl sulfate sodium salt is widely marketed as a detergent and shampoo ingredient (oral LD q 1268 mg/kg for rats) (126). Both dimethyl sulfate and monomethyl sulfate occur in the environment in coal fly-ash and in airborne particulate matter (130). 

The degree to which inhaled gases, vapors, and particulates are absorbed, and hence their potential to produce systemic toxicity, depends on their solubihty in tissue fluids, any metaboHsm by lung tissue, diffusion rates, and equiUbrium state. 

The bioavailability, and hence the toxicity, of metal depends on the physical and chemical form of the metal, which in turn depends on the chemical characteristics of the surrounding water. The dissolved form of the metal is generally viewed as more bioavailable and therefore more toxic than the particulate form. Particiilate matter and dissolved organic matter can bind the metal, making it less bioavailable. What is not well known or documented is the various chemical transformations that occur both within the effluent stream and when the effluent reaches and mixes with the receiving water. Metal that is not bioavailable in the effluent may become bioavailable under ambient chemical conditions. 

Heavy metals on or in vegetation and water have been and continue to be toxic to animals and fish. Arsenic and lead from smelters, molybdenum from steel plants, and mercury from chlorine-caustic plants are major offenders. Poisoning of aquatic life by mercury is relatively new, whereas the toxic effects of the other metals have been largely eliminated by proper control of industrial emissions. Gaseous (and particulate) fluorides have caused injury and damage to a wide variety of animals—domestic and wild—as well as to fish. Accidental effects resulting from insecticides and nerve gas have been reported. 

Pollutant (if particulate) Size range and distribution Particle shape Agglomeration tendencies Corrosiveness Abrasiveness Hygroscopic tendencies Stickiness InflanunabiUty Toxicity Electrical resistivity Reactivity... 

Toxic, flammable/explosive, reactive, unstable Liquid, solid (briquette, flake, powder), gas, vapour, ah-borne particulate (including mist, fume, froth, aerosol, dust)... 

---