Rationale for an Eight-Hour Ozone Standard

As part of the exposure assessment scheme for a community-based air pollution health effects study, 43 homes of study participants, located in two Houston neighborhoods, were monitored for weekly-average indoor formaldehyde levels by means of diffusion samplers. Consecutive 12-hour aldehyde sampling for one-week periods was conducted in 12 of the homes by means of pumps and impingers. In six houses where simultaneous monitoring with both methods occurred, good correlation between the results from the diffusion samplers and the standard impinger method was observed. Diffusion sampler precision was variable and lower than expected, and a small positive measurement bias could be inferred. The distribution of house-average indoor formaldehyde concentrations from diffusion monitoring was similar to that obtained during a previous housing survey in Houston, with concentrations in 19 percent of the homes exceeding 0.10 ppm. Formaldehyde levels in this group of conventional, mostly older homes could not be associated with smoking, cooking, home age or structure type. However, there was a statistically significant difference between mean indoor concentrations in the two neighborhoods.     

Reduction in residential chromium following site remediation

The purpose of this study was to determine the influence of chromate production waste site remediation on residential Cr concentrations in house dust. Twenty-three homes in Jersey City, NJ, were identified as having had high (> 500 micrograms/gm, median 739 micrograms/gm), medium (100-400 micrograms/gm, median 245 micrograms/gm), or low (< 100 micrograms/gm, median 48 micrograms/gm) Cr in house dust during a study conducted in 1992-1993 prior to site remediation. House dust samples were collected on four visits from each home between November 1996 and February 1998, extracted with HNO3, and analyzed for Cr with an inductively coupled plasma-mass spectrometer. Homes that had low Cr concentrations in 1992-1993 continued to have low Cr concentrations (median 1 microgram/g). In contrast, substantial declines in Cr concentrations were found in the house dust collected from homes located near the remediated waste sites: previously high-level homes had a median of 50 micrograms/g and mid-level homes had a median of 34 micrograms/g. Site remediation had a beneficial effect on household loadings of Cr, since no differences in post-remediation house dust Cr concentrations were found among the three groups.     

Effect of temperature and humidity on formaldehyde emissions in temporary housing units

The effect of temperature and humidity on formaldehyde emissions from samples collected from temporary housing units (THUs) was studied. The THUs were supplied by the U.S. Federal Emergency Management Administration (FEMA) to families that lost their homes in Louisiana and Mississippi during the Hurricane Katrina and Rita disasters. On the basis of a previous study, four of the composite wood surface materials that dominated contributions to indoor formaldehyde were selected to analyze the effects of temperature and humidity on the emission factors. Humidity equilibration experiments were carried out on two of the samples to determine how long the samples take to equilibrate with the surrounding environmental conditions. Small chamber experiments were then conducted to measure emission factors for the four surface materials at various temperature and humidity conditions. The samples were analyzed for formaldehyde via high-performance liquid chromatography. The experiments showed that increases in temperature or humidity contributed to an increase in emission factors. A linear regression model was built using the natural log of the percent relative humidity (RH) and inverse of temperature (in K) as independent variables and the natural log of emission factors as the dependent variable. The coefficients for the inverse of temperature and log RH with log emission factor were found to be statistically significant for all of the samples at the 95% confidence level. This study should assist in retrospectively estimating indoor formaldehyde exposure of occupants of THUs.     

Reduction in Residential Chromium Following Site Remediation

ABSTRACT

The purpose of this study was to determine the influence of chromate production waste site remediation on residential Cr concentrations in house dust. Twenty-three homes in Jersey City, NJ, were identified as having had high (>500 u,g/gm, median 739 u,g/gm), medium (100-400 u,g/gm, median 245 u,g/gm), or low (<100 u,g/gm, median 48 u,g/ gm) Cr in house dust during a study conducted in 19921993 prior to site remediation. House dust samples were collected on four visits from each home between November 1996 and February 1998, extracted with HNO₃, and analyzed for Cr with an inductively coupled plasma-mass spectrometer. Homes that had low Cr concentrations in 1992-1993 continued to have low Cr concentrations (median 1 u,g/g). In contrast, substantial declines in Cr concentrations were found in the house dust collected from homes located near the remediated waste sites: previously high-level homes had a median of 50 u,g/g and mid-level homes had a median of 34 u,g/g. Site remediation had a beneficial effect on household loadings of Cr, since no differences in post-remediation house dust Cr concentrations were found among the three groups.     

Benzene exposure and the effect of traffic pollution in Copenhagen,Denmark

Benzene is a carcinogenic compound, which is emitted from petrol-fuelled cars and thus is found ubiquitous in all cities. As part of the project Monitoring of Atmospheric Concentrations of Benzene in European Towns and Homes (MACBETH) six campaigns were carried out in the Municipality of Copenhagen, Denmark. The campaigns were distributed over 1 year. In each campaign, the personal exposure to benzene of 50 volunteers (non-smokers living in non-smoking families) living and working in Copenhagen was measured. Simultaneously, benzene was measured in their homes and in an urban network distributed over the municipality. The Radiello diffusive sampler was applied to sample 5 days averages of benzene and other hydrocarbons. Comparison of the results with those from a BTX-monitor showed excellent agreement. The exposure and the concentrations in homes and in the urban area were found to be close to log-normal distribution. The annual averages of the geometrical mean values were 5.22, 4.30 and 2.90 μg m⁻³ for personal exposure, home concentrations and urban concentrations, respectively. Two main parameters are controlling the general level of benzene in Copenhagen: firstly, the emission from traffic and secondly, dispersion due to wind speed. The general level of exposure to benzene and home concentrations of benzene were strongly correlated with the outdoor level of benzene, which indicated that traffic is an important source for indoor concentrations of benzene and for the exposure to benzene.     

Formaldehyde personal exposure measurements and time weighted exposure estimates in children

Residential concentrations of formaldehyde have been associated with poor respiratory health in children, where formaldehyde has been measured using stationary monitors inside homes. Although children spend most of their time indoors at home, there are few studies of children’s personal exposure to formaldehyde. The aim of this study was to investigate the relationship between personal exposure formaldehyde concentrations, microenvironmental concentrations and time weighted exposure estimates in children.Forty-one primary school children (aged between 9 and 12 years) wore a personal passive sampler over two 24 h periods in two seasons and completed 24 h daily activity diaries and a questionnaire about lifestyle and behaviour. Samplers were co located indoors at home, outdoors at centralised locations and indoors at school for the corresponding period.Personal exposure formaldehyde concentrations in this group of children were generally low with a geometric mean concentration of 9.1 ppb (range <detection limit to 27.3 ppb). There were strong correlations between personal exposure concentrations and both domestic indoor (r_s = .779, p < 0.001) and time weighted estimated (r_s = .802, p < 0.001) concentrations. The time weighted model did not improve the estimate of personal exposure compared with stationary indoor concentrations. Indoor air concentration measured with a single stationary monitor was a suitable surrogate for personal exposure.     

Predicting personal exposure to airborne carbonyls using residential measurements and time/activity data

As a part of the Relationships of Indoor, Outdoor, and Personal Air (RIOPA) study, 48 h integrated residential indoor, outdoor, and personal exposure concentrations of 10 carbonyls were simultaneously measured in 234 homes selected from three US cities using the Passive Aldehydes and Ketones Samplers (PAKS). In this paper, we examine the feasibility of using residential indoor concentrations to predict personal exposures to carbonyls. Based on paired t-tests, the means of indoor concentrations were not different from those of personal exposure concentrations for eight out of the 10 measured carbonyls, indicating indoor carbonyls concentrations, in general, well predicted the central tendency of personal exposure concentrations. In a linear regression model, indoor concentrations explained 47%, 55%, and 65% of personal exposure variance for formaldehyde, acetaldehyde, and hexaldehyde, respectively. The predictability of indoor concentrations on cross-individual variability in personal exposure for the other carbonyls was poorer, explaining<20% of variance for acetone, acrolein, crotonaldehyde, and glyoxal. A factor analysis, coupled with multiple linear regression analyses, was also performed to examine the impact of human activities on personal exposure concentrations. It was found that activities related to driving a vehicle and performing yard work had significant impacts on personal exposures to a few carbonyls.     

Commuter exposures to VOCs in Boston, Massachusetts.

This study examines the commuter's exposure to six gasoline-related volatile organic compounds (VOCs): benzene, toluene, ethylbenzene, m-/p-xylene, o-xylene, and formaldehyde. The VOC concentrations to which commuters were exposed in four different commuting modes (driving, subway, walking, and biking) in Boston, Massachusetts, are compared. The VOC concentrations in participants' homes and offices were also measured. Factors that could influence in-vehicle VOC concentrations, such as different traffic patterns, car model and vehicle ventilation conditions, were also evaluated. Driving a private car was associated with higher VOC concentrations and commuting on urban roadways resulted in the highest VOC concentrations. The use of car heaters resulted in higher in-vehicle VOC concentrations. The longer the subway commuters stayed underground, the higher their VOC exposures. The home-to-work car or subway commute represented about 10 to 20 percent of an individual's total VOC exposure for these compounds.     

Ozone decay rates in residences

In urban and suburban settings, indoor ozone exposures can represent a significant fraction of an individual's total exposure. The decay rate, one of the factors determining indoor ozone concentrations, is inadequately understood in residences. Decay rates were calculated by introducing outdoor air containing 80-160 parts per billion ozone into 43 residences and monitoring the reduction in indoor concentration as a function of time. The mean decay rate measured in the living rooms of 43 Southern California homes was 2.80 +/- 1.30 hr-1, with an average ozone deposition velocity of 0.049 +/- 0.017 cm/sec. The experimental protocol was evaluated for precision by repeating measurements in one residence on five different days, collecting 44 same-day replicate measurements, and by simultaneous measurements at two locations in six homes. Measured decay rates were significantly correlated with house type and the number of bedrooms. The observed decay rates were higher in multiple-family homes and homes with fewer than three bedrooms. Homes with higher surface-area-to-volume ratios had higher decay rates. The ratio of indoor-to-outdoor ozone concentrations in homes not using air conditioning and open windows was 68 +/- 18%, while the ratio of indoor-to-outdoor ozone was less than 10% for the homes with air conditioning in use.     

Monitoring of carbon monoxide in residences with bulk wood pellet storage in the Northeast United States

The interest in biomass fuel is continuing to expand globally and in the northeastern United States as wood pellets are becoming a primary source of fuel for residential and small commercial systems. Wood pellets for boilers are often stored in basement storage rooms or large bag-type containers. Due to the enclosed nature of these storage areas, the atmosphere may exhibit increased levels of carbon monoxide. Serious accidents in Europe have been reported over the last decade in which high concentrations of carbon monoxide (CO) have been found in or near bulk pellet storage containers. The aim of this study was to characterize the CO concentrations in areas with indoor storage of bulk wood pellets. Data was obtained over approximately 7 months (December 2013 to June 2014) at 25 sites in New Hampshire and Massachusetts: 16 homes using wood pellet boilers with indoor pellet storage containers greater than or equal to 3 ton capacity; 4 homes with wood pellet heating systems with outdoor pellet storage; 4 homes using other heating fuels; and a university laboratory site. CO monitors were set up in homes to collect concentrations of CO in the immediate vicinity of wood pellet storage containers, and data were then compared to those of homes using fossil fuel systems. The homes monitored in this study provided a diverse set of housing stock spanning two and a half centuries of construction, with homes built from 1774 to 2013, representing a range of air exchange rates. The CO concentration data from each home was averaged hourly and then compared to a threshold of 9 ppm. While concentrations of CO were generally low for the homes studied, the need to properly design storage locations for pellets is and will remain a necessary component of wood pellet heating systems to minimize the risk of CO exposure.

Implications: This paper is an assessment of carbon monoxide (CO) exposure from bulk wood pellet storage in homes in New Hampshire and Massachusetts. Understanding the CO concentrations in homes allows for better designs for storage bins and ventilation for storage areas. Hence, uniform policies for stored wood pellets in homes, schools, and businesses can be framed to ensure occupant safety. Currently in New York State rebates for the installation of wood pellet boilers are only provided if the bulk pellet storage is outside of the home, yet states such as New Hampshire, Vermont, and Maine currently do not have these restrictions.     

Formaldehyde Dose-Response in Healthy Nonsmokers

Industrial, commercial, and domestic levels of formaldehyde exposure range from <0.1 to >5.0 ppm. Irritation of the eyes and upper respiratory tract predominate, and bronchoconstriction is described in case reports. However, pulmonary function and irritant symptoms together have not been assessed over a range of HCHO concentrations in a controlled environment. We investigated dose response in both symptoms and pulmonary function associated with 3-h exposures to 0.0-3.0 ppm HCHO in a controlled environmental chamber. Ten subjects were randomly exposed to 0.0, 0.5, 1.0, and 2.0 ppm HCHO at rest plus 2.0 ppm HCHO with exercise and nine additional subjects were randomly exposed to 0.0,1.0,2.0, and 3.0 ppm HCHO at rest plus 2.0 ppm HCHO with exercise. Significant dose-response relationships in odor and eye irritation were observed (p < 0.05). Nasal flow resistance was increased at 3.0 ppm (p < 0.01), but not at 2.0 ppm HCHO. There were no significant decrements in pulmonary function (FVC, FEV₁, FEF_25-75%, SGaw) or increases in bronchial reactivity to methacholine (log PD_35SGaw) with exposure to 0.5-3.0 ppm HCHO at rest or to 2.0 ppm HCHO with exercise.     

Commuter Exposures to VOCs in Boston,Massachusetts

This study examines the commuter’s exposure to six gasoline-related volatile organic compounds (VOCs): benzene, toluene, ethylbenzene, m-/p-xylene, o-xylene, and formaldehyde. The VOC concentrations to which commuters were exposed in four different commuting modes (driving, subway, walking, and biking) in Boston, Massachusetts, are compared. The VOC concentrations in participants’ homes and offices were also measured. Factors that could influence in-vehicle VOC concentrations, such as different traffic patterns, car model and vehicle ventilation conditions, were also evaluated. Driving a private car was associated with higher VOC concentrations and commuting on urban roadways resulted in the highest VOC concentrations. The use of car heaters resulted in higher in-vehicle VOC concentrations. The longer the subway commuters stayed underground, the higher their VOC exposures. The home-to-work car or subway commute represented about 10 to 20 percent of an individual’s total VOC exposure for these compounds.     

Formation of strong airway irritants in a model mixture of (+)-α-pinene/ozone

The airway irritation of (+)-α-pinene, ozone, mixtures thereof, and formaldehyde was evaluated by a mouse bioassay, in which sensory irritation, bronchoconstriction, and pulmonary irritation were measured. The effects are distinguished by analysis of the respiratory parameters. Significant sensory irritation (assessed from reduction of mean respiratory rate) was observed by dynamic exposure of the mice, over a period of 30 min, to a ca. 22 s old reaction mixture of ozone and (+)-α-pinene from a Teflon flow tube. The starting concentrations were 6 ppm and 80 ppm, respectively, which were diluted and let into the exposure chamber. About 10% ozone remained unreacted (0.4 ppm), <0.2 ppm formaldehyde, <0.4 ppm pinonaldehyde, <2 ppm formic acid, and <1 ppm acetic acid were formed. These concentrations, as well as that of the unreacted (+)-α-pinene (51 ppm), were below established no effect levels. The mean reduction of the respiratory rate (30%) was significantly different (p≪0.001) from clean air, as well as from exposure of (+)-α-pinene, ozone, and formaldehyde themselves at the concentrations measured. Addition of the effects of the measured residual reactants and products cannot explain the observed sensory irritation effect. This suggests that one or more strong airway irritants have been formed. Therefore, oxidation reactions of common naturally occurring unsaturated compounds (e.g., terpenes) may be relevant for indoor air quality.     

Ozone Decay Rates in Residences

ABSTRACT

In urban and suburban settings, indoor ozone exposures can represent a significant fraction of an individual's total exposure. The decay rate, one of the factors determining indoor ozone concentrations, is inadequately understood in residences. Decay rates were calculated by introducing outdoor air containing 80-160 parts per billion ozone into 43 residences and monitoring the reduction in indoor concentration as a function of time. The mean decay rate measured in the living rooms of 43 Southern California homes was 2.80 + 1.30 hr^-1, with an average ozone deposition velocity of 0.049 + 0.017 cm/sec. The experimental protocol was evaluated for precision by repeating measurements in one residence on five different days, collecting 44 same-day replicate measurements, and by simultaneous measurements at two locations in six homes. Measured decay rates were significantly correlated with house type and the number of bedrooms. The observed decay rates were higher in multiple-family homes and homes with fewer than three bedrooms. Homes with higher surface-area-to-volume ratios had higher decay rates. The ratio of indoor-to-outdoor ozone concentrations in homes not using air conditioning and open windows was 68 + 18%, while the ratio of indoor-to-outdoor ozone was less than 10% for the homes with air conditioning in use.     

Alteration in Carboxyhemoglobin Concentrations During Exposure to 9 ppm Carbon Monoxide for 8 Hours at Sea Level and 2134 m Altitude in a Hypobaric Chamber

Seventeen non-smoking young men served as subjects to determine the alteration in carboxyhemoglobin (COHb) concentrations during exposure to 0 or 9 ppm carbon monoxide for 8 hours (CO) at sea level or an altitude of 2134 meters (7000 feet) in a hypobaric chamber. Nine subjects rested during the exposure and 8 exercised for 10 minutes of each exposure hour at a mean ventilation of 25 L (BTPS). All subjects performed a maximal aerobic capacity test at the completion of their respective exposures. Carboxyhemoglobin concentrations fell in all subjects during their exposures to 0 ppm CO at sea level or 2134 m. During the 8-h exposures to 9 ppm CO, COHb rose linearly from approximately 0.2 percent to 0.7 percent. No significant differences in uptake were found whether the subjects were resting or intermittently exercising during their 8-h exposures. COHb levels attained were similar at both sea level and 2134 m. Maximal aerobic capacity was reduced approximately 7-10 percent consequent to altitude exposure during 0 ppm CO exposures. These values were not altered following exposure for 8 h to 9 ppm CO in either the resting or exercising subjects.     

Sperm count in earthworms (Lumbricus terrestris) as a biomarker for environmental toxicology: effects of cadmium and chlordane

Earthworms, Lumbricus terrestris, exposed in artificial soil to sublethal concentrations of technical chlordane (6.25, 12.5, and 25 ppm) and cadmium nitrate (100, 200, and 300 ppm) exhibited significant reduction in spermatozoa from testes and seminal vesicles. The onset time of reduction varied with exposure concentration, but absolute depression in sperm count was independent of exposure concentration or exposure duration after reduction was first manifested, demonstrating a threshold effect. Earthworm sperm counts show potential as a rapid-measurement endpoint biomarker for measuring sublethal effects of chemical pollutants on reproduction.     

Vehicle Occupant Exposure to Carbon Monoxide

Abstract

This paper focuses on the auto commuting micro-environment and presents typical carbon monoxide (CO) concentrations to which auto commuters in central Riyadh, Saudi Arabia were exposed. Two test vehicles traveling over four main arterial roadways were monitored for inside and outside CO levels during eighty peak and off-peak hours extending over an eight month period. The relative importance of several variables which explained the variability in CO concentrations inside autos was also assessed. It was found that during peak hours auto commuters were exposed to mean CO levels that ranged from 30 to 40 ppm over trips that typically took between 25 to 40 minutes. The mean ratio of inside to outside CO levels was 0.84. Results of variance component analyses indicated that the most important variables affecting CO concentrations inside autos were, in addition to the smoking of vehicle occupants, traffic volume, vehicle speed, period of day and wind velocity. An increase in traffic volume from 1,000 to 5,000 vehicles per hour (vph) increased mean CO level exposure by 71 percent. An increase in vehicle speed from 14 to 55 km/h reduced mean CO exposure by 36 percent. The number of traffic interruptions had a moderate effect on mean concentrations of CO inside vehicles.     

Indoor pollutant levels from the use of unvented natural gas fireplaces in Boulder, Colorado

High CO and NO2 concentrations have been documented in homes with unvented combustion appliances, such as natural gas fireplaces. In addition, polycyclic aromatic hydrocarbons (PAH) are emitted from incomplete natural gas combustion. The acute health risks of CO and NO2 exposure have been well established for the general population and for certain high-risk groups, including infants, the elderly, and people with heart disease or asthma. Health effects from PAH exposure are less well known, but may include increased risk of cancer. We monitored CO emissions during the operation of unvented natural gas fireplaces in two residences in Boulder, CO, at various times between 1997 and 2000. During 1999, we expanded our tests to include measurements of NO2 and PAH. Results show significant pollutant accumulation indoors when the fireplaces were used for extended periods of time. In one case, CO concentrations greater than 100 ppm accumulated in under 2 hr of operation; a person at rest exposed for 10 hr to this environment would get a mild case of CO poisoning with an estimated 10% carboxyhemoglobin level. Appreciable NO2 concentrations were also detected, with a 4-hr time average reaching 0.36 ppm. Similar time-average total PAH concentrations reached 35 ng/m3. The results of this study provide preliminary insights to potential indoor air quality problems in homes operating unvented natural gas fireplaces in Boulder.     

Evaluation of a Probabilistic Exposure Model Applied

The probabilistic National Ambient Air Quality Standards (NAAQS) Exposure Model applied to carbon monoxide (pNEM/CO) was developed by the U.S. Environmental Protection Agency (EPA) to estimate frequency distributions of population exposure to carbon monoxide (CO) and the resulting carboxyhemoglobin (COHb) levels. To evaluate pNEM/CO, the model was set up to simulate CO exposure data collected during a Denver Personal Exposure Monitoring Study (PEM) conducted during the winter of 1982-1983.

This paper compares computer-simulated exposure distributions obtained by pNEM/CO with the observed cumulative

relative frequency distributions of population exposure to CO from 779 people in the Denver PEM study. The subjects were disaggregated into two categories depending upon whether they lived in a home with a gas stove or an electric stove. The observed and predicted population exposure frequency distributions were compared in terms of 1-hr daily maximum exposure (1DME) and 8-hr daily maximum moving average exposure (8DME) for people living in homes with gas stove or an electric stove. For 1DME, the computer-simulated results from pNEM/CO agreed most closely within the range of 6-13 ppm, but overestimated occurrences at low exposure (<6 ppm) and underestimated occurrences at high exposure (>13 ppm). For 8DME, the predicted exposures agreed best with observed exposures in the range of CO concentration between 5.5 and 7 ppm, and over-predicted occurrences below 5.5 ppm and under-predicted occurrences above 7 ppm.     

Evaluation of a Probabilistic Exposure Model Applied to Carbon Monoxide (pNEM/CO) Using Denver Personal Exposure Monitoring Data

The probabilistic National Ambient Air Quality Standards (NAAQS) Exposure Model applied to carbon monoxide (pNEM/CO) was developed by the U.S. Environmental Protection Agency (EPA) to estimate frequency distributions of population exposure to carbon monoxide (CO) and the resulting carboxyhemoglobin (COHb) levels. To evaluate pNEM/CO, the model was set up to simulate CO exposure data collected during a Denver Personal Exposure Monitoring Study (PEM) conducted during the winter of 1982-1983. This paper compares computer-simulated exposure distributions obtained by pNEM/CO with the observed cumulative relative frequency distributions of population exposure to CO from 779 people in the Denver PEM study.

The subjects were disaggregated into two categories depending upon whether they lived in a home with a gas stove or an electric stove. The observed and predicted population exposure frequency distributions were compared in terms of 1-hr daily maximum exposure (1DME) and 8-hr daily maximum moving average exposure (8DME) for people living in homes with gas stove or an electric stove. For 1DME, the

computer-simulated results from pNEM/CO agreed most closely within the range of 6-13 ppm, but overestimated occurrences at low exposure (<6 ppm) and underestimated occurrences at high exposure (>13 ppm). For 8DME, the predicted exposures agreed best with observed exposures in the range of CO concentration between 5.5 and 7 ppm, and over-predicted occurrences below 5.5 ppm and under-predicted occurrences above 7 ppm.