The amount of water on a Teflon surface is roughly three times larger at 70% RH compared to 50% RH, 504 apparently influencing the uptake and subsequent release of HONO from that surface. While exposed Teflon surfaces are rare indoors, carpets and upholstery are commonly treated with perfluorocarbon surfactants. Absent the influences of oxidative aging and/or soiling, such highly hydrophobic surfaces are unlikely to play a role in acid-base chemistry or to serve as reservoirs for gaseous acids or bases. Polarizability is the ability of a substance to form a dipole when exposed to an electric field. Won et al. examined the relationship between the polarizability of eight gas-phase organics and different indoor surfaces, including carpet, gypsum board, upholstery, vinyl flooring, wood flooring, and acoustic tiles. For nonpolar organics, carpet was a strong sorptive sink. For highly polar organics, virgin gypsum board was a substantial sink. Ongwandee et al. measured the partitioning of five sorbates, including nicotine and phenol, to polypropylene and PVC surfaces. Polypropylene is nonpolar, whereas PVC is polar. They also used previously reported data to examine correlations between hexadecane/air partitioning coefficients and surface polarity. They found that for weak bases, sorption correlated well with a sorbate’s hexadecane/air partitioning coefficient regardless of surface polarity. In contrast, for strong bases, surface polarity was important. No correlations were found for sorption to fleecy or plush materials such as carpet.Elsewhere,seedling grow rack we have discussed studies demonstrating that indoor surfaces are large reservoirs for nitrous, formic, acetic, propionic, butyric, and pentanoic acids, for ammonia, and for nicotine.
Surfaces are also demonstrated to be reservoirs for “total SVOCs,”which includes numerous higher molecular weight organics with acid functionality. Theory indicates that the same should be true for other acidic and basic compounds found in indoor air. Species such as nitrous acid, C1-C5 carboxylic acids, and ammonia have a much larger fraction of their mass in indoor surface reservoirs than in the gas-phase. This feature has been clearly illustrated in so called venting experiments in which the gas-phase concentration of a species quickly returns to a prior steady-state concentration after a short period of enhanced ventilation. Surface reservoirs of acidic and basic species are sensitive to temperature; indoor gas-phase concentrations of the acids and bases display fine-scale temperature dependent increases and decreases in concentration corresponding to increases and decreases in temperature. It should be noted that strong inorganic acids interact with indoor surfaces chiefly as a consequence of the water associated with these surfaces. The extent to which an indoor surface serves as a reservoir for strong inorganic acids depends on the water associated with the surface and its pH, as well as the pKa and KH of the inorganic acid in question. Organic acids and bases, in addition to interacting with water on or in surfaces, also interact with organic surface films and exposed polymeric materials. The extent to which an indoor surface serves as a reservoir for gas-phase organic acids also depends on the abundance of organic sorptive reservoirs in contact with air, as well as with the relevant partition coefficient of the organic acid or base. Relatively simple mass-balance models and the selected physical chemical properties of a given organic acid or base serve to explain and can be used to predict such behavior.
Wang et al. present phase-partitioning plots that illustrate indoor gas-surface partitioning of various species, including some common organic acids. These plots adapt a scheme first presented to address a three-part phase distribution – gaseous, aqueous phase, and condensed organic phase – of chemicals involved in the outdoor formation of secondary aerosols . When considering the role that surfaces play as reservoirs for indoor acids and bases, painted surfaces and stained wood surfaces warrant special comment since such surfaces account for almost two-thirds of the total indoor surface area in the surveys conducted by Hodgson et al. and Manuja et al.Paint experimentally applied to tin-plated steel “to obtain a surface similar to a painted wall” yielded thicknesses in the range 25-63 µm. The combination of a layer of primer and two layers of paint applied to drywall has a total thickness of 75-125 µm.As the amount of pigment in a paint film increases, its porosity increases. Above a pigment volume concentration of 40 to 50%, the permeability is fairly large, meaning that most commercial paints are permeable enough for gas-phase acids and bases to diffuse through them at meaningful rates. This assumption regarding diffusivity is reinforced by recent measurements . As noted in Table 2, the equilibrium moisture content of latex paint is 0.35% at 30% RH and 0.86% at 50% RH. Hence, at 50% RH, a 100 µm layer of paint contains moisture equivalent to a water film whose thickness is of order 1 µm. Such water might serve as a significant sink for highly water-soluble gas-phase organic acids . Gas-phase organic acids could also partition into the organic polymer that constitutes the surface of dry paint. Algrim et al. have made the first extensive measurements of partitioning between various gas-phase organics, including C3-C7 carboxylic acids, and paint films. For C3-, C5-, C6 and C7-carboxylic acids, the paint film/air partition coefficients were 4.3 ´ 105 , 7.5 ´ 105 , 16 ´ 105 , and 39 ´ 105, respectively. These values are relatively close to the corresponding octanol-air partition coefficients , suggesting that Koa can serve as a quantitative indicator for partitioning of carboxylic acids to painted surfaces.
Algrim et al. also measured diffusion coefficients in the paint films and the fraction of a given organic that completely penetrated a paint film to reach the underlying wallboard. The diffusion coefficients of C3-C7 carboxylic acids in paint films coated onto glass walls of flow tubes were between 10-9 and 10-10 cm2 s-1 at 22 °C and correlated with the vapor pressure of the species. Related experiments indicated that the full volume of the paint film was available for absorption. A large fraction of the carboxylic acids penetrated the paint film after partitioning to it, suggesting the likelihood of further uptake by the underlying substrate. Clothing may serve as mobile reservoirs for acids and bases. For example, substantial nicotine may sorb to clothing surfaces in one indoor environment and then be transferred to a different indoor environment where the nicotine then redistributes to other indoor compartments. One may anticipate that the presence of acidic or basic species influences reactions that occur in or on indoor surface materials. The time constraint that limits gas-phase chemistry to the scale of hours does not apply to reactions on surfaces. Hence,greenhouse growing racks acid- or base-catalyzed hydrolysis is much more important on indoor surfaces than in the gas phase. A well-known example involves PVC flooring plasticized with di phthalate atop moist concrete.The alkaline environment promotes the hydrolysis of DEHP to form 2-ethylhexanol and mono phthalate . Under similar conditions, the plasticizer di phthalate undergoes hydrolysis to form n-butanol and mono phthalate . The hydrolysis of DEHP in dust has been shown to be larger at elevated relative humidities, and it is anticipated that the same is true for DEHP in weakly polar organic surface films. Odaka et al. have reported that, when soybean oil was added to lime plaster, hexaldehyde was strongly emitted. When linseed oil was added, propionaldehyde was emitted; and when perilla oil was added, acetaldehyde was emitted. One envisions that similar chemistry could occur in a lime-walled kitchen when cooking with vegetable oils. In certain cases, surfaces are intentionally modified to promote reactive chemistry. An example is the use of TiO2 as an oxidation catalyst in wall paints. Upon illumination, the TiO2 particles generate hydroxyl radicals. Such paints have been demonstrated to influence indoor concentrations of oxidized organics and nitrogen oxides.
We have discussed the manner in which surfaces can serve as reservoirs for gas-phase species and how surfaces can catalyze reactions, either by design or unintentionally. Surfaces also harbor an indoor microbiome. The bacterial and fungal communities on indoor surfaces have a complex relationship with the surfaces’ chemical nature. The pH of aqueous surface films influences which bacterial or fungal species thrive, and, in turn, bacterial and fungal species influence surface pH. In the latter instance, bacterial and fungal species can alter the pH of surface moisture to promote their own growth.Cannabis and tobacco use are common among adolescents in the U.S. In this paper, we will refer to marijuana use rather than cannabis use since we will be discussing exposure to the psychoactive drug delta-9-tetrahydrocannabinol , and some cannabis products contain the non-psychoactive cannabinoids without THC. Nationally representative Monitoring the Future survey data from 2017 indicates that lifetime prevalence of marijuana use in middle and high schoolers was 29%, with 15% using in the past 30-days . A Washington State survey from 2014 to 2016 similarly found an 18% report of past 30-day marijuana use in students from grades 8 to 12 . Recreational marijuana was legalized in Washington in 2012. Tobacco cigarette lifetime prevalence was 17%, with 5% smoking within the past 30-days. In surveys of adolescents, cigarette smokers are much more likely to smoke marijuana than those who do not use tobacco products . Some adolescents smoke tobacco and marijuana together in the form of blunts – hollowed out cigars filled with marijuana . Others smoke mixtures of tobacco and marijuana . A high prevalence of co-use of tobacco and marijuana in adolescents has raised a number of health concerns . Co-users of tobacco and marijuana are more likely to experience mental health problems compared to those who use either alone . Co-users are less likely to quit marijuana use and are more likely to experience cannabis use disorder . Conversely, some research indicates that co-users have more difficulty quitting smoking cigarettes .Animal studies report that nicotine augments pharmacologic responses to THC, including increasing the rewarding effects, attenuation of development of tolerance, enhancement of antagonist-precipitated withdrawal and long-lasting brain biochemical changes . Genetic studies indicate a common genetic predisposition to tobacco and marijuana use, and cannabinoid receptor genes appears to be related to nicotine dependence . Assessing tobacco and marijuana exposure, both prevalence and level of exposure in adolescents is important in epidemiologic studies of harm from nicotine and cannabis, particularly as marijuana use is being legalized in more and more states in the U.S. and around the world. Most data on the prevalence of marijuana and tobacco use come from self-reports, which may suffer from misreporting. Few studies have used biochemical screening to assess exposure. In a study of 12–19 year olds receiving medical care in an outpatient clinic, urine samples were screened via an immunoassay and found that 24% of the sample were positive for THC . Tobacco cigarette smoking status was not asked or analyzed biochemically. In children ages 1 month to 2 years hospitalized for bronchiolitis, 16% had evidence of marijuana exposure; and exposure was more likely when there was biochemical evidence of tobacco exposure . Another study screened hospitalized children with a parent in smoking cessation treatment for THC in urine, finding that 46% of children had detectable levels of 11-nor-9-carboxy-THC , a primary metabolite of THC that can detect both active and passive marijuana smoke exposure . Cotinine, the primary proximate metabolite of nicotine, was also measured in urine; cotinine and THC-COOH levels were not significantly correlated. We have published studies on biochemical screening for active and passive cigarette smoking in adolescents attending pediatric clinics in a public hospital in San Francisco . Here we present data on biochemically-determined marijuana use in the same population. Our aims were to compare high sensitivity quantitative testing vs a commonly used immunoassay screening test and self-report of THC use, examine demographics of marijuana exposure, and determine qualitative and quantitative aspects of the concordance of marijuana and tobacco use. Biochemical assessment of marijuana involved measurement of the THC metabolite THCCOOH in urine. THC-COOH has a relatively long half-life and typical urine screening tests remain positive for 30 hours after a single use and for as long as 30 days after abstinence in a heavy regular marijuana user . Biochemical assessment of tobacco use was performed by measuring levels in urine of cotinine, the main proximate metabolite of nicotine which has a half-life averaging 16 hr, and the tobacco-specific nitrosamine, 4–l–1-butanol , which has a half-life of 10–16 days and is a biomarker of long term tobacco use .