Acute and Chronic Exposures

When an individual receives a relatively large dose over a single (or brief) time period, we refer to this type of exposure as acute. An 

No matter which mode of entry a toxin takes, the health effects can be either local or systemic, depending upon the physical and chemical characteristics of the substance. Local effects are the tissue reactions of the body areas that come in direct contact with the contaminant. Systemic effects, on the other hand, occur in the target sites of the body, which are not the initial contact locations, but which, because of their affinity for that particular substance, readily absorb it. This reaction may occur far away from the point of initial contact. If an employee were working with sulfuric acid and inhaled sufficient quantities of it, irritation of the upper respiratory system would be likely (irritation of the nose, bronchi, trachea, etc.). Inhalation of heavy metals, such as lead, would have systemic effects (lead does not have a substantial impact upon the respiratory system, which in this case is the site of contact). However, the primary dangers from lead are to the central nervous system, the blood, and the kidneys. 

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Fig. 7. Toxicity of chlorine to aquatic organisms, (a) Time-dependent mortaUty (50%) of four example species in various levels of total residual chlorine in the laboratory, where for A, A.losa aestivalis and B, Salmogairdnerii r (correlation coefficient of the curve) = —0.96 and for C, P/euroneetesplatessa and D, Salmo trutta r = —0.98. (b) A summary of chlorine toxicity to freshwater species, indicating overall no-effect thresholds for acute and chronic exposures. Numbers indicate where more than one test yielded the same result. A different summary figure appHes to marine organisms because of differences in the...

Although the effects of chronic exposure of humans to low levels of POPs are difficult to predict, some biological effects have been described. For example, exposure of children to PCBs and PCDD/Fs may be linked to an elevated risk for infectious diseases. Exposure of pregnant women to PCDD/Fs may cause lower fertility in their male offspring. The adverse effects to human health of acute and chronic exposure of high concentrations of POPs, especially among industrial workers exposed to daily intakes of chemicals, are more evident. Elevated concentrations of DDE and TCDD have been associated with the development of cancers such as breast cancer, leukaemia and thyroid cancer. Dioxin exposure may also be associated with immunotoxicity, reproductive diseases and neurotoxicity. Extreme exposure to chlorinated compounds has resulted in death [101]. 

Brown, D.A., S.M. Bay, and G.P. Hershelman. 1990. Exposure of scorpionfish Scorpaena guttata) to cadmium effects of acute and chronic exposures on the cytosolic distribution of cadmium, copper and zinc. Aquat. Toxicol. 16 295-310. 

Visviki, L. and J.W. Rachlin. 1994a. Acute and chronic exposure of Dunaliella salina and Chlamydomonas bullosa to copper and cadmium effects on growth. Arch. Environ. Contam. Toxicol. 26 149-153. 

Toluene Clear, colorless liquid with a slight fire hazard and moderate explosion hazard. Entry into the body is mostly by vapor inhalation. Acute and chronic exposures occur with concentrations greater than 200 ppm. Irritant to skin and eyes. 

Pacifici, R. et al., Immunosuppression and oxidative stress induced by acute and chronic exposure to cocaine in rat, Ini. Immunopharmacol., 3, 581, 2003. 

HCFC-141b is a colorless, volatile liquid with a weak, ethereal odor. The vapor is heavier than air and can displace air in confined spaces. Additional chemical and physical properties are listed in Table 4-2. Experimental studies with human subjects and several mammalian species (monkey, dog, rat, mouse, and rabbit) were located. Animal studies addressed both acute and chronic exposure durations as well as neurotoxicity, genotoxicity, carcinogenicity, and cardiac sensitization. 

The primary target for cyanide toxicity is the central nervous system following both acute and chronic exposure. Exposure to high doses of cyanide can rapidly lead to death (see Section 2.2). Cyanide is not stored in the organism and one available study indicates that >50% of the received dose can be eliminated within 24 hours (Okoh 1983). However, because of the rapid toxic action of cyanide, development of methods that would enhance metabolism and elimination of cyanide is warranted. 

Aii SF, Newport GD, Scaiiet AC, Pauie MG, Baiiey JR, Siikker W Jr. (1991). Chronic marijuana smoke exposure in the rhesus monkey IV. Neurochemicai effects and comparison to acute and chronic exposure to deita-9-tetrahydrocannabinoi (THC) in rats. Pharmacol Biochem Behav. 40(3) 677-82. Bachman JA, Benowitz NL, Herning RI, Jones RT. (1979). Dissociation of autonomic and cognitive effects of THC in man. Psychopharmacology (Berlin). 61(2) 171-75. 

The general chemical structure of N-methyl carbamate is shown in Fig. 4.4. Common N-methyl carbamates in use today include aldicarb, carbofuran, methiocarb, oxamyl, and carbaryl. N-methyl carbamates share with organophosphates the capacity to inhibit cholinesterase enzymes and, therefore, share similar symptomology during acute and chronic exposure. 

Renal damage has been reported after both acute and chronic exposure. Mercury is known to accumulate in the kidneys, and case studies have described increased creatinine excretion, proteinuria, hematuria, and degeneration of the convoluted tubules in exposed individuals. Increased levels of the urinary enzyme NAG (AT-acetyl-P-glycosaminidase), compared with controls, have been observed in chronically exposed workers. ... 

The only significant source of information on this subject was published by Leidel et al. (15) of NIOSH, who suggested air sampling schemes for both acute and chronic exposures. Regarding acute exposures the authors made an important distinction between environments in which the period of highest short-term exposure can be predicted and those where this is not possible. This ability or inability to predict the highest exposure dictates the type of air sampling scheme. 

Toluene toxicity is most prominent in the central nervous system after acute and chronic exposure. Reproductive toxicity has been observed in exposed humans and rats. 

The USEPA acute and chronic exposure criteria for the safety of freshwater aquatic biota are both < 100 ng/L for azinphos-methyl, chlorpyrifos, malathion, and parathion (Table 8). Existing guidelines for the protection of aquatic life and for drinking water were not exceeded for any of the OP insecticides analyzed. 

Inhalation studies in humans and animals and oral studies in animals demonstrate that chlorobenzene can affect the central nervous system, liver, and kidneys. Chlorobenzene did not affect the developing fetus, was not genotoxic, and did not affect reproduction. Data has not provided clear evidence that chlorobenzene causes cancer in animals. Existing data are considered inadequate to derive human minimal risk levels for acute and chronic exposures. 

Toxicity O-Nitrotoluene causes adverse effects to animals and humans. Acute and chronic exposure causes irritation to skin and mucous membranes, hypoxia, anemia, and depression in workers.86 More reports are available regarding the genotoxicity, carcinogenicity, and reproductive effects of O-Nitrotoluene in experimental animals.87,88... 

HRAs are a means of estimating the potential for an adverse effect on a select population upon exposure to a single chemical or mixture of chemicals. This risk is generally defined as a function of the concentration of chemical(s) to which an individual of known size and specified characteristics is exposed, for a given period of time, via ingestion, inhalation, or dermal contact. HRAs are performed for acute and chronic exposures of both on-site and off-site populations. 

The LD50 values and all reliable LOAEL values for death in each species following acute and chronic exposure are recorded in Table 2-2 and plotted in Figure 2-2. 

Toxicity and health effects Exposure to o-nitrotoluene causes adverse effects in animals and humans. Acute and chronic exposure causes headache, skin irritation, flushing of face, dizziness, dyspnea, hypoxia, cyanosis, nausea, vomiting, muscular weakness, increased pulse and respiratory rate, irritability, and convulsions. ... 

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