Chemicals exposure levels

R. Craig Matthiessen, Estimating Chemical Exposure Levels in the Workplace, Chemical Engineering Progress (April 1986), p. 30. 

Few reports are available on the potential effect of chemical concentration on the BAF in an aquatic organism (e.g., Mayer, 1976). Yet, a key assumption of EP theory is the independency of BAF relative to exposure concentration. To our knowledge, there is only one report (Huckins et al., 2004) in the peer-reviewed literature, where the effect of chemical exposure level on concentration factors (CFs) or BAFs has been tested in side-by-side BMO and passive sampler exposures. Huckins et al. (2004) defined CF as the ratio of the concentration in a sample matrix (whole body [soft tissues in the case of bivalves] or whole SPMDs) relative to the concentration in the ambient exposure medium at any moment in time, whereas the A sw and BAF (includes biomagnilication) represent the maximal CF. Similar to ATs s and BAFs, CFs are expected to be independent of exposure concentrations, when residue exchange follows first-order kinetics. 

In a manner analogous to the hazard index approach for noncarcinogens, hazard quotients for carcinogenic mixture components can be estimated by dividing chemical exposure levels by doses (DR) associated with a set level of cancer risk the HI is the sum of the HQ values [9,16] ... 

Matthiessen, R. C. (1986). Estimating chemical exposure levels in the workplace WeH-characlerized monitoring data are needed to assess worker exposure levels dming the manufacture, processing, and use of industrial chemicals. Chem Eng Prog, 30-34. 

CFR1910.120(g)(3)(iii) 4.5.2 Positive pressure self-contained breathing apparatus, or positive pressure air-line respirators equipped with an escape air supply shall be used when chemical exposure levels present will create a substantial possibility of immediate death, immediate serious illness or injury, or impair the ability to escape. 

Both PEL and TLV refer to toxic chemical exposure levels. Just remember, the PEL values of toxic chemicals are published by OSHA, while the TLV values are published by the ACGIH. You can find PEL values on the OSHA Web site (www.osha.gov). Look under regulations. PEL values refer to inhalation exposure. TLV values are published by ACGIH annually. Most chemicals have identical PEL and TLV values. 

Most of the selected female reproductive toxicology studies examined explicitly stated chemical exposure levels either as parts per million, stratifying as to number of days of exposure, or as estimates of the percentage of the threshold limit values. Medline, Toxline, and Dissertation Abstracts databases were utilized to search for all research papers published in any language from 1966 to 1996. In total, 559 studies were obtained from the literature search. Of these, only 21 studies explicitly stated some sort of exposure level for the various chemicals. These chemical exposure levels in the literature and subsequent pregnancy outcomes were compared to lOL chemical exposure indices. The following is an example of one of the many chemical exposures encountered, namely exposure to toluene. For other compounds, Table 20.3.5 contrasts values in the literature with lOL indices of chemical exposure. 

Upon comparing the occupational literature that presented any quantifiable chemical exposure dose or estimate of dose for any chemical with the lOL routine rating factors in the Products and Chemicals Divisions, we could conclude that lOL chemical exposure levels overall were lower than those reported in the literature. Of utmost importance is the need in published occupational reports for at least some industrial hygiene documentation, namely improved reporting of a quantifiable chemical exposure dose (for example, as implemented and currently utilized by lOL) and ideally a standard and consistent way of reporting fliis in the occupational literature. 

Health and Safety Factors. Terephthahc acid has a low order of toxicity. Inhalation by rats for 6 h/d, 5 d/wk for 4 wk produced no fatahties at a dust exposure level of 25 mg/m. The mean acute oral toxicity for rats is over 18 g/kg (86), and for mice over 6 g/kg (87). When terephthahc acid was fed as 3% of the diet to rats, urinary calcuh formed in 90 d, some of which led to cancer. High doses of terephthahc acid lead to formation of calcium terephthalate at levels exceeding its solubihty in urine. This insoluble material leads to the calcuh and provides a threshold below which cancer is not observed (88). Normal precautions used in handling industrial chemicals should be observed with terephthahc acid. If ventilation is inadequate, a toxic-dust respirator should be used to avoid prolonged exposure. 

Ashford, N., and Miller, C. (1998J Chemical Exposures, High Levels and High Stakes, 2nd edn. Van Nostrand Remhold, New York. 

The threshold for toxic injury is not the same for everyone because sensitivity varies greatly among individuals. Most chemicals in consumer products remain untested for health effects, such as cancer, reproductive problems, and the impacts of long-term, low level exposure. How these substances affect women, children, and people with existing conditions is also little studied. Once a person s defenses have been broken down and he or she has become hypersensitive, a wide variety of common chemical exposures can trigger a reaction. Just what products and other chemicals which cause problems varies greatly among affected individuals. 

Chronic Health Effect A chronic health effect is an adverse health effect resulting from long-term exposure to a substance. The effects could be a skin rash, bronchitis, cancer, or any other medical condition. An example would be liver cancer from inhaling low levels of benzene at your workplace over several years. The term is also applied to a persistent (months, years, or permanent) adverse health effect resulting from a short-term (acute) exposure. Chronic effects from long-term exposure to chemicals are fairly common. Recognize the PEL (permissible exposure level) for each substance in your workplace and minimize your exposure whenever possible. 

Typical units for LDjq values are milligrams or grams of material per kilogram of body weight (mg/kg or g/kg, recall that 1 kg = 2.2 pounds). Never be exposed to an LD50 dose of a hazardous chemical- by definition, there is a 50% chance this will kill you and if you survive you are not going to be in good shape. Pay close attention to the permissible exposure level (PEL) instead. This is a more realistic determination of the maximum safe exposure to a material and is usually based on the known effects of the chemical on humans, rather than laboratory animals. 

The hazards of chemicals are commonly detected in the workplace first, because exposure levels there are higher than in the general environment. In addition, the exposed population is well known, which allows early detection of the association between deleterious health effects and the exposure. The toxic effects of some chemicals, such as mercury compounds and soot, have been known already for centuries. Already at the end of the eighteenth century, small boys who were employed to climb up the inside of chimneys to clean them suffered from a cancer of the scrotum due to exposure to soot. This was the first occupational cancer ever identified. In the viscose industry, exposure to carbon disulfide was already known to cause psychoses among exposed workers during the nineteenth century. As late as the 1970s, vinyl chloride was found to induce angiosarcoma of the liver, a tumor that was practically unknown in ocher instances. ... 

Risk assessment, a synthesis of the preceding three steps, which aims to assess both qualitatively and quantitatively the risks induced by a chemical at a given or at different exposure levels. 

The biotransformation of a given chemical compound in experimental animals and in humans may differ. Furthermore, high doses of chemical compounds are used in studies with experimental animals, and this may cause alterations in biotransformation of the tested chemicals that do not occur at the lower doses relevant to the human exposure situation. For example, a metabolic pathway dominating at low doses may become saturated, and a salvage metabolic pathway, e.g., one that produces reactive intermediates of the compound, may become involved in the biotransformation of the chemical. Since this intermediate could never be produced at the exposure levels encountered in humans, the overall result... 

The chances are generally not die same. Exposure depends on both die amount of clicinical exposure and die frequency of chemical exposure. Repealed exposure to low levels of a mix of chemicals may be linked to liealdi problems. However, a single incident at a higher level, if below a toxic direshold, may not be linked to liealdi problems. 

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