Dose-Response Analysis Using Spreadsheets

The task of fitting dose-response models to experimental data can be performed using a spreadsheet with a built-in optimization engine. This paper shows how the task of point and interval estimation can be performed using Microsoft EXCEL. A case study is presented on the carcinogenic dose-response behavior of chloroform.     

Exposure to Chlorination By-Products from Hot Water Uses

Exposures to chlorination by-products (CBP) within public water supplies are multiroute in water. Cold water is primarily used for ingestion while a mixture of cold water and hot water is used for showering, bathing others, dish washing, etc. These latter two activities result in inhalation and dermal exposure. Heating water was observed to change the concentration of various CBP. An increase in the trihalomethanes (THM) concentrations and a decrease in the haloacetonitriles and halopropanones concentration, though an initial rise in the concentration of dichloropropanone, were observed. The extent of the increase in the THM is dependent on the chlorine residual present. Therefore, estimates of total exposure to CBP from public water supplies need to consider any changes in their concentration with different water uses. The overall THM exposures calculated using the THM concentration in heated water were 50% higher than those calculated using the THM concentration present in cold water. The estimated lifetime cancer risk associated with exposure to THM in water during the shower is therefore underestimated by 50% if the concentration of THM in cold water is used in the risk assessment.     

极谱法测定水中微量氯仿

在乙二胺EDTA底液中,氯仿在负的1.68V产生一灵敏的极谱吸收波,氯仿的浓度在2.06×10~(-6)～1.23×10~(-2)mol.L~(-1)的范围内与导数波有线性关系,检测限为1.00×10~(-5)mol.L~(-1),应用本法可直接测定漂白废水中的氯仿。经预先富集后对自来水的氯仿也能进行测定。并取得满意结果。     

Routes of Chloroform Exposure and Body Burden from Showering with Chlorinated Tap Water

While there is an awareness of the need to quantify inhalation exposure from showers, the potential for dermal exposure to organic contaminants in showers has not been appreciated or explored. To establish routes of environmental exposure from showers, comparisons of the concentration of chloroform in exhaled breath after a normal shower with municipal tap water were made with those after an inhalation-only exposure. The postexposure chloroform breath concentrations ranged from 6.0-21 micrograms/m3 for normal showers and 2.4 to 10 micrograms/m3 for inhalation-only exposure, while the pre-exposure concentrations were all less than the minimum detection limit of 0.86 micrograms/m3. According to an F-test, the difference between the normal shower and the inhalation-only exposures was considered significant at a probability of p = 0.0001. Based on the difference, the mean internal dose due to dermal exposure was found to be approximately equal to that due to the inhalation exposure. The effect of the showering activities on the concentration of chloroform shower air was examined by comparing air concentrations during a normal shower with the air concentrations obtained when the shower was unoccupied. The F-test showed that there is no significant difference between the two sets of data.     

Chloroform Exposure and the Health Risk Associated with Multiple Uses of Chlorinated Tap Water

Recently, showers have been suspected to be an important source of indoor exposure to volatile organic compounds (VOC). The chloroform dose to an individual from showering was determined based on exhaled breath analysis. The postexposure chloroform breath concentration ranged from 6.0-21 micrograms/m3, while all corresponding background breath concentrations were less than 0.86 micrograms/m3. The internal dose from showering (inhalation plus dermal) was comparable to estimates of the dose from daily water ingestion. The risk associated with a single, 10-min shower was estimated to be 1.22 x 10(-4), while the estimated risk from daily ingestion of tap water ranged from 0.130 x 10(-4) to 1.80 x 10(-4) for 0.15 and 2.0 L, respectively. Since the estimates of chloroform risk from domestic water use for the three exposure routes--ingestion, inhalation, and dermal--are similar, all routes must be used to calculate the total risk when making policy decisions regarding the quality of the municipal water supply.