Bedroom Concentrations and Emissions of Volatile Organic Compounds during Sleep.

Because humans spend about one-third of their time asleep in their bedrooms and are themselves emission sources of volatile organic compounds (VOCs), it is important to specifically characterize the composition of the bedroom air that they experience during sleep. This work uses real-time indoor and outdoor measurements of volatile organic compounds (VOCs) to examine concentration enhancements in bedroom air during sleep and to calculate VOC emission rates associated with sleeping occupants. Gaseous VOCs were measured with proton-transfer reaction time-of-flight mass spectrometry during a multiweek residential monitoring campaign under normal occupancy conditions. Results indicate high emissions of nearly 100 VOCs and other species in the bedroom during sleeping periods as compared to the levels in other rooms of the same residence. Air change rates for the bedroom and, correspondingly, emission rates of sleeping-associated VOCs were determined for two bounding conditions: (1) air exchange between the bedroom and outdoors only and (2) air exchange between the bedroom and other indoor spaces only (as represented by measurements in the kitchen). VOCs from skin oil oxidation and personal care products were present, revealing that many emission pathways can be important occupant-associated emission factors affecting bedroom air composition in addition to direct emissions from building materials and furnishings.

Model Framework for Predicting Semivolatile Organic Material Emissions Indoors from Organic Aerosol Measurements: Applications to HOMEChem Stir-Frying.

Cooking activities emit myriad low-volatility, semivolatile, and highly volatile organic compounds that together form particles that can accumulate to large indoor concentrations. Absorptive partitioning thermodynamics governs the particle-phase organic aerosol concentration mainly via temperature and sorbing mass impacts. Cooking activities can increase the organic sorbing mass by 1-2 orders of magnitude, increasing particle-phase concentrations and affecting emission rate calculations. Although recent studies have begun to probe the volatility characteristics of indoor cooking particles, parametrizations of cooking particle mass emissions have largely neglected these thermodynamic considerations. Here, we present an improved thermodynamics-based model framework for estimating condensable organic material emission rates from a time series of observed concentrations, given that adequate measurements or assumptions can be made about the volatility of the emitted species. We demonstrate the performance of this methodology by applying data from stir-frying experiments performed during the House Observations of Microbial and Environmental Chemistry (HOMEChem) campaign to a two-zone box model representing the UTest House. Preliminary estimates of organic mass emitted on a per-stir-fry basis for three types of organic aerosol factors are presented. Our analysis highlights that using traditional nonvolatile particle models and emission characterizations for some organic aerosol emitting activities can incorrectly attribute concentration changes to emissions rather than thermodynamic effects.

Volatile Methyl Siloxanes and Other Organosilicon Compounds in Residential Air.

Volatile methyl siloxanes (VMS) are ubiquitous in indoor environments due to their use in personal care products. This paper builds on previous work identifying sources of VMS by synthesizing time-resolved proton-transfer reaction time-of-flight mass spectrometer VMS concentration measurements from four multiweek indoor air campaigns to elucidate emission sources and removal processes. Temporal patterns of VMS emissions display both continuous and episodic behavior, with the relative importance varying among species. We find that the cyclic siloxane D5 is consistently the most abundant VMS species, mainly attributable to personal care product use. Two other cyclic siloxanes, D3 and D4, are emitted from oven and personal care product use, with continuous sources also apparent. Two linear siloxanes, L4 and L5, are also emitted from personal care product use, with apparent additional continuous sources. We report measurements for three other organosilicon compounds found in personal care products. The primary air removal pathway of the species examined in this paper is ventilation to the outdoors, which has implications for atmospheric chemistry. The net removal rate is slower for linear siloxanes, which persist for days indoors after episodic release events. This work highlights the diversity in sources of organosilicon species and their persistence indoors.

Contrasting Chemical Complexity and the Reactive Organic Carbon Budget of Indoor and Outdoor Air.

Reactive organic carbon (ROC) comprises a substantial fraction of the total atmospheric carbon budget. Emissions of ROC fuel atmospheric oxidation chemistry to produce secondary pollutants including ozone, carbon dioxide, and particulate matter. Compared to the outdoor atmosphere, the indoor organic carbon budget is comparatively understudied. We characterized indoor ROC in a test house during unoccupied, cooking, and cleaning scenarios using various online mass spectrometry and gas chromatography measurements of gaseous and particulate organics. Cooking greatly impacted indoor ROC concentrations and bulk physicochemical properties (e.g., volatility and oxidation state), while cleaning yielded relatively insubstantial changes. Additionally, cooking enhanced the reactivities of hydroxyl radicals and ozone toward indoor ROC. We observed consistently higher median ROC concentrations indoors (≥223 µg C m-3) compared to outdoors (54 µg C m-3), demonstrating that buildings can be a net source of reactive carbon to the outdoor atmosphere, following its removal by ventilation. We estimate the unoccupied test house emitted 0.7 g C day-1 from ROC to outdoors. Indoor ROC emissions may thus play an important role in air quality and secondary pollutant formation outdoors, particularly in urban and suburban areas, and indoors during the use of oxidant-generating air purifiers.

Efficacy of outpatient infusion therapy in pediatric patients with postconcussive headaches.

PURPOSE: To determine the relative efficacy of intravenous therapy for postconcussive headaches in a pediatric population, as compared to oral therapy. METHODS: Pediatric patients treated for postconcussive headaches at an outpatient infusion clinic from 2016 to 2018 were selected for inclusion in the study. Of the 95 patients who were treated in clinic, 53 patients were selected for a retrospective chart review. Clinic visits before and after infusions were reviewed to determine changes in headache score (HA), symptom severity score (SSS), and self-reported symptom relief. An age-matched and SSS-matched group served as a control. The control group received only oral therapy for their headaches. The infusion consisted of parenteral ketorolac, compazine, diphenhydramine, and a normal saline bolus (20 mg/kg). RESULTS: Following infusion therapy, overall mean HA and SSS scores were both reduced (p < 0.0001). Oral therapy demonstrated a similar mean overall reduction in HA and SS scores (p < 0.0001). While both groups achieved a reduction in HA and SS scores, there was not a statistically significant difference in reduction of symptoms scores between the oral and infusion groups. CONCLUSION: Infusion therapy is as effective at reducing HA and SSS as established oral therapies. Infusion therapy may have a shorter time to headache abortion than oral therapy based on pharmacokinetics. Further, some physicians are unwilling to allow an athlete to return to play while taking suppressive medication. Future studies may show that an infusion could allow a more rapid return to play and resolution of symptoms.

Real-time organic aerosol chemical speciation in the indoor environment using extractive electrospray ionization mass spectrometry.

Understanding the sources and composition of organic aerosol (OA) in indoor environments requires rapid measurements, since many emissions and processes have short timescales. However, real-time molecular-level OA measurements have not been reported indoors. Here, we present quantitative measurements, at a time resolution of five seconds, of molecular ions corresponding to diverse aerosol-phase species, by applying extractive electrospray ionization mass spectrometry (EESI-MS) to indoor air analysis for the first time, as part of the highly instrumented HOMEChem field study. We demonstrate how the complex spectra of EESI-MS are screened in order to extract chemical information and investigate the possibility of interference from gas-phase semivolatile species. During experiments that simulated the Thanksgiving US holiday meal preparation, EESI-MS quantified multiple species, including fatty acids, carbohydrates, siloxanes, and phthalates. Intercomparisons with Aerosol Mass Spectrometer (AMS) and Scanning Mobility Particle Sizer suggest that EESI-MS quantified a large fraction of OA. Comparisons with FIGAERO-CIMS shows similar signal levels and good correlation, with a range of 100 for the relative sensitivities. Comparisons with SV-TAG for phthalates and with SV-TAG and AMS for total siloxanes also show strong correlation. EESI-MS observations can be used with gas-phase measurements to identify co-emitted gas- and aerosol-phase species, and this is demonstrated using complementary gas-phase PTR-MS observations.

Indoor Particulate Matter during HOMEChem: Concentrations, Size Distributions, and Exposures.

It is important to improve our understanding of exposure to particulate matter (PM) in residences because of associated health risks. The HOMEChem campaign was conducted to investigate indoor chemistry in a manufactured test house during prescribed everyday activities, such as cooking, cleaning, and opening doors and windows. This paper focuses on measured size distributions of PM (0.001-20 µm), along with estimated exposures and respiratory-tract deposition. Number concentrations were highest for sub-10 nm particles during cooking using a propane-fueled stovetop. During some cooking activities, calculated PM2.5 mass concentrations (assuming a density of 1 g cm-3) exceeded 250 µg m-3, and exposure during the postcooking decay phase exceeded that of the cooking period itself. The modeled PM respiratory deposition for an adult residing in the test house kitchen for 12 h varied from 7 µg on a day with no indoor activities to 68 µg during a simulated day (including breakfast, lunch, and dinner preparation interspersed by cleaning activities) and rose to 149 µg during a simulated Thanksgiving day.

Chemical and Physical Characterization of 3D Printer Aerosol Emissions with and without a Filter Attachment.

Fused filament fabrication three-dimensional (3D) printers have been shown to emit ultrafine particles (UFPs) and volatile organic compounds (VOCs). Previous studies have quantified bulk 3D printer particle and VOC emission rates, as well as described particle chemical composition via ex situ analysis. Here, we present size-resolved aerosol composition measurements from in situ aerosol mass spectrometry and ex situ transmission electron microscopy (TEM). Particles were sampled for in situ analysis during acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) 3D printing activities and ex situ analysis during ABS printing. We examined the effect of a high-efficiency particulate air filter attachment on ABS emissions and particle chemical composition and demonstrate that filtration was effective in preventing UFP emissions and that particles sampled during filtered prints did not have a high contribution (∼4% vs ∼10%) from aromatic ions in the mass spectrum. Ex situ analysis of particles collected during ABS printing was performed via TEM and electron energy loss spectroscopy, which indicated a high level of sp2 bonding type consistent with polymeric styrene. One 3D print with PLA resulted in an aerosol mass size distribution with a peak at ∼300 nm. Unfiltered ABS prints resulted in particle mass size distributions with peak diameters of ∼100 nm.

Surface Emissions Modulate Indoor SVOC Concentrations through Volatility-Dependent Partitioning.

Measurements by semivolatile thermal desorption aerosol gas chromatography (SV-TAG) were used to investigate how semivolatile organic compounds (SVOCs) partition among indoor reservoirs in (1) a manufactured test house under controlled conditions (HOMEChem campaign) and (2) a single-family residence when vacant (H2 campaign). Data for phthalate diesters and siloxanes suggest that volatility-dependent partitioning processes modulate airborne SVOC concentrations through interactions with surface-laden condensed-phase reservoirs. Airborne concentrations of SVOCs with vapor pressures in the range of C13 to C23 alkanes were observed to be correlated with indoor air temperature. Observed temperature dependencies were quantitatively similar to theoretical predictions that assumed a surface-air boundary layer with equilibrium partitioning maintained at the air-surface interface. Airborne concentrations of SVOCs with vapor pressures corresponding to C25 to C31 alkanes correlated with airborne particle mass concentration. For SVOCs with higher vapor pressures, which are expected to be predominantly gaseous, correlations with particle mass concentration were weak or nonexistent. During primary particle emission events, enhanced gas-phase emissions from condensed-phase reservoirs partitioned to airborne particles, contributing substantially to organic particulate matter. An emission event related to oven-usage was inferred to deposit siloxanes in condensed-phase reservoirs throughout the house, leading to the possibility of reemission during subsequent periods with high particle loading.

Multiphase Chemistry Controls Inorganic Chlorinated and Nitrogenated Compounds in Indoor Air during Bleach Cleaning.

We report elevated levels of gaseous inorganic chlorinated and nitrogenated compounds in indoor air while cleaning with a commercial bleach solution during the House Observations of Microbial and Environmental Chemistry field campaign in summer 2018. Hypochlorous acid (HOCl), chlorine (Cl2), and nitryl chloride (ClNO2) reached part-per-billion by volume levels indoors during bleach cleaning-several orders of magnitude higher than typically measured in the outdoor atmosphere. Kinetic modeling revealed that multiphase chemistry plays a central role in controlling indoor chlorine and reactive nitrogen chemistry during these periods. Cl2 production occurred via heterogeneous reactions of HOCl on indoor surfaces. ClNO2 and chloramine (NH2Cl, NHCl2, NCl3) production occurred in the applied bleach via aqueous reactions involving nitrite (NO2-) and ammonia (NH3), respectively. Aqueous-phase and surface chemistry resulted in elevated levels of gas-phase nitrogen dioxide (NO2). We predict hydroxyl (OH) and chlorine (Cl) radical production during these periods (106 and 107 molecules cm-3 s-1, respectively) driven by HOCl and Cl2 photolysis. Ventilation and photolysis accounted for <50% and <0.1% total loss of bleach-related compounds from indoor air, respectively; we conclude that uptake to indoor surfaces is an important additional loss process. Indoor HOCl and nitrogen trichloride (NCl3) mixing ratios during bleach cleaning reported herein are likely detrimental to human health.

Observations and Contributions of Real-Time Indoor Ammonia Concentrations during HOMEChem.

Although ammonia (NH3) is usually found at outdoor concentrations of 1-5 ppb, indoor ammonia concentrations can be much higher. Indoor ammonia is strongly emitted from cleaning products, tobacco smoke, building materials, and humans. Because of ammonia's high reactivity, solubility in water, and tendency to sorb to a variety of surfaces, it is difficult to measure, and thus a comprehensive evaluation of indoor ammonia concentrations remains an understudied topic. During HOMEChem, which was a comprehensive indoor chemistry study occurring in a test house during June 2018, the real-time concentration of ammonia indoors was measured using cavity ring-down spectroscopy. A mean unoccupied background concentration of 32 ppb was observed, with further enhancements of ammonia occurring during cooking, cleaning, and occupancy activities, reaching maximum concentrations during these activities of 130, 1592, and 99 ppb, respectively. Furthermore, ammonia concentrations were strongly influenced by indoor temperatures and heating, ventilation, and air conditioning (HVAC) operation. In the absence of activity-based sources, the HVAC operation was the main modulator of ammonia concentration indoors.

Once daily oral extended-release hydrocodone as analgesia following tibial plateau leveling osteotomy in dogs.

OBJECTIVE: To determine the efficacy of oral extended-release hydrocodone compared with oral firocoxib for analgesia following tibial plateau leveling osteotomy surgery in dogs in a hospital setting. STUDY DESIGN: Prospective, randomized, blinded, clinical trial. ANIMALS: Thirty-six client-owned dogs weighing 25-43 kg with unilateral hindlimb lameness and cranial cruciate ligament rupture. METHODS: Dogs were assigned to 1 of 2 groups (n = 18/group). Group 1 received hydrocodone 3 mg/kg orally every 24 hours, and group 2 received firocoxib 5 mg/kg orally every 24 hours. Both hydrocodone and firocoxib (according to group assignment) were provided as preemptive analgesia 10 hours before induction to anesthesia and then every 24 hours for the remainder of the study period The level of analgesia was compared between treatments on the basis of a modified Glasgow Composite Pain Score (mGCPS) in each dog, the number of dogs requiring rescue analgesia (hydromorphone 0.05 mg/kg subcutaneously), pressure platform stance data, and number of adverse events. RESULTS: Nine of 18 dogs that received hydrocodone and 2/18 dogs that received firocoxib had an mGCPS ≥6 (P = .02). Two dogs had an mGCPS ≥6 three times, and 1 had an mGCPS ≥6 two times; all 3 of these dogs were in the hydrocodone group. Average postoperative peak pressure placed on the affected limb was lower in dogs that received hydrocodone (P = .01). Regurgitation and decreased appetite were more common in the dogs that received hydrocodone. CONCLUSION: Dogs that were treated with hydrocodone exhibited higher pain scores and lower limb function than dogs treated with firocoxib under the conditions of our study. CLINICAL SIGNIFICANCE: Our results do not provide evidence to justify the administration of extended-release hydrocodone at 3 mg/kg orally every 24 hours rather than firocoxib at 5 mg/kg orally every 24 hours in dogs undergoing tibial plateau leveling osteotomy.

Independent effects of early-life experience and trait aggression on cardiovascular function.

Early-life experience (ELE) can significantly affect life-long health and disease, including cardiovascular function. Specific dimensions of emotionality also modify risk of disease, and aggressive traits along with social inhibition have been established as independent vulnerability factors for the progression of cardiovascular disease. Yet, the biological mechanisms mediating these associations remain poorly understood. The present study utilized the inherently stress-susceptible and socially inhibited Wistar-Kyoto rats to determine the potential influences of ELE and trait aggression (TA) on cardiovascular parameters throughout the lifespan. Pups were exposed to maternal separation (MS), consisting of daily 3-h separations of the entire litter from postnatal day (P)1 to P14. The rats were weaned at P21, and as adults were instrumented for chronic radiotelemetry recordings of blood pressure and heart rate (HR). Adult aggressive behavior was assessed using the resident-intruder test, which demonstrated that TA was independent of MS exposure. MS-exposed animals (irrespective of TA) had significantly lower resting HR accompanied by increases in HR variability. No effects of MS on resting blood pressure were detected. In contrast, TA correlated with increased resting mean, systolic, and diastolic arterial pressures but had no effect on HR. TA rats (relative to nonaggressive animals) also manifested increased wall-to-lumen ratio in the thoracic aorta, increased sensitivity to phenylephrine-induced vascular contractility, and increased norepinephrine content in the heart. Together these data suggest that ELE and TA are independent factors that impact baseline cardiovascular function.

Extruded alginate tubes with myogenic potential.

BACKGROUND: There are currently no proven methods to reverse muscle loss in humans, which is caused by trauma (e.g., volumetric muscle loss, VML), genetic neuromuscular diseases (e.g., muscular dystrophies, MDs), and accelerated senescence (e.g., sarcopenia). Since muscle tissue is capable of regeneration through muscle satellite cells (MuSCs), the implantation of autologous (or other) donor MuSCs and MuSC-derived myoblasts into host muscles can promote donor-cell-derived myogenesis. Direct injection or implantation of MuSCs or MuSC-derived myoblasts into host muscles only promotes minimal donor-cell-derived myogenesis, whereas implantation of MuSCs/myoblasts along with associated muscle tissue (muscle fibers, extracellular matrix, neurovascular pathways, etc.) gives better results. METHODS: We aim to leverage the benefits of constraining donor myogenic cells within a template that resembles muscle tissue. In this paper, we present a workflow for basic and translational studies aimed at promoting donor-cell-derived myogenesis to increase functional muscle mass in mice. Our workflow involves preparing a slurry of 10% sodium alginate mixed with myogenic cells in cell culture media, extruding the cell-containing slurry into 10% calcium lactate to form tubes, and implanting the cellularized alginate tubes into host muscle. RESULTS: Our data suggest that, the extruded alginate tubes can tolerate a peak stress of 1892 ± 527 mN, that the elastic range is at ~75-125% strain beyond initial length, and that the Young's modulus (stiffness) is 14.17 ± 1.68 %/mm2. Importantly, these mechanical properties render the alginate tubes suitable for a published technique known as minimally-invasive muscle embedding (MIME) that was developed by us to implant myogenic material into host muscle. MIME involves threading donor myogenic tissue into a needle track created within a host muscle. Cellularized alginate tubes implanted into the tibialis anterior muscle of previously euthanized mice had numerous hematoxylin-stained structures similar to nuclear staining, supporting the idea that our alginate tubes can support cell seeding. Alginate tubes that were seeded with MuSCs, incubated in MuSC/myoblast growth (i.e., proliferation) media for two days, incubated in myotube differentiation media for six days, and then minced and reseeded in new dishes, were able to promote in vitro myoblast outgrowth over several days. DISCUSSION: This pilot study is limited in its translational scope because it was performed in vitro and with previously euthanized mice. Additional studies are needed to confirm that cellularized alginate tubes can promote the de novo development of donor-cell-derived muscle fibers, which can contribute to contractile force production. CONCLUSION: Alginate tubes with MuSC/myoblasts can be generated by a simple extrusion method. The alginate tubes have sufficient mechanical strength to tolerate insertion into a host muscle, in a minimally-invasive manner, through a needle track. The cellularized alginate tubes demonstrate myogenic potential since they are capable of being maintained in culture conditions for several days, after which they can still facilitate myoblast outgrowth in a dish.

Indoor black carbon and brown carbon concentrations from cooking and outdoor penetration: insights from the HOMEChem study.

Particle emissions from cooking are a major contributor to residential indoor air pollution and could also contribute to ambient concentrations. An important constituent of these emissions is light-absorbing carbon, including black carbon (BC) and brown carbon (BrC). This work characterizes the contributions of indoor and outdoor sources of BC and BrC to the indoor environment by concurrently measuring real-time concentrations of these air pollutants indoors and outdoors during the month-long HOMEChem study. The median indoor-to-outdoor ratios of BC and BrC during the periods of no activity inside the test house were 0.6 and 0.7, respectively. The absorption Ångström exponent was used to characterize light-absorbing particle emissions during different activities and ranged from 1.1 to 2.7 throughout the campaign, with the highest value (indicative of BrC-dominated emissions) observed during the preparation of a simulated Thanksgiving Day holiday style meal. An indoor BC exposure assessment shows that exposure for an occupant present in the kitchen area was ∼4 times higher during Thanksgiving Day experiments (primarily due to candle burning) when compared to the background conditions.

Emerging investigator series: chemical and physical properties of organic mixtures on indoor surfaces during HOMEChem.

Organic films on indoor surfaces serve as a medium for reactions and for partitioning of semi-volatile organic compounds and thus play an important role in indoor chemistry. However, the chemical and physical properties of these films are poorly characterized. Here, we investigate the chemical composition of an organic film collected during the HOMEChem campaign, over three cumulative weeks in the kitchen, using both Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) and offline Aerosol Mass Spectrometry (AMS). We also characterize the viscosity of this film using a model based on molecular formulas as well as poke-flow measurements. We find that the film contains organic material similar to cooking organic aerosol (COA) measured during the campaign using on-line AMS. However, the average molecular formula observed using FT-ICR MS is ∼C50H90O11, which is larger and more oxidized than fresh COA. Solvent extracted film material is a low viscous semisolid, with a measured viscosity <104 Pa s. This is much lower than the viscosity model predicts, which is parametrized with atmospherically relevant organic molecules, but sensitivity tests demonstrate that including unsaturation can explain the differences. The presence of unsaturation is supported by reactions of film material with ozone. In contrast to the solvent extract, manually removed material appears to be highly viscous, highlighting the need for continued work understanding both viscosity measurements as well as parameterizations for modeled viscosity of indoor organic films.

The Stability and Efficacy of Tricaine Methanesulfonate (MS222) Solution After Long-Term Storage.

Tricaine methanesulfonate (MS222) is widely used for the anesthesia and euthanasia of laboratory zebrafish. Fresh solutions have been recommended for each use; however, researchers often mix and store concentrated stock solutions for convenience and to reduce occupational exposure and environmental waste. While this is common practice, published guidelines are often inconsistent. Thus, the objective of this study was to evaluate the stability and anesthetic efficacy of MS222 after long-term storage and to develop specific storage parameters. Stock solutions (100 mg/mL MS222) were mixed and stored in amber jars at 4 °C and -20 °C for 2- and 6-mo. Stability of the solutions was analyzed using liquid chromatography-ion trapmass spectrometry and compared with fresh MS222. Fifty adult (30 male, 20 female) wildtype AB zebrafish (Danio rerio) wererandomly anesthetized with 150 mg/L of one of the following MS222 solutions to evaluate anesthetic efficacy: 1) freshly prepared(0m); 2) 2 mo at 4 °C (2m4); 3) 2 mo at -20 °C (2m-20); 4) 6 mo at 4 °C (6m4); 5) 6 mo at -20 °C (6m-20). Time to cessation of swimming, loss of equilibrium, lack of response to von Frey (VF) stimulation, return of equilibrium, and resumption of swimming were compared between groups. Two fish from each group were euthanized at 24-h and 2-wk after anesthesia, and histopathology was performed. All solutions were determined to be stable under all storage conditions. No clinically significant differences were observed between the fresh and stored stock groups during anesthetic testing. No evidence ofanesthetic-related histologic changes were noted in the gills, skin, kidneys, muscle, and central nervous system. Hepatic megalocytosis and a reduction in hepatic vacuolation were seen to varying degrees across all groups, but did not follow a treatment-related trend. Therefore, 100 mg/mL solutions of MS222 can be stored in amber jars at 4 °C or -20 °C for 6 mo and still used to effectively anesthetize zebrafish.

Evaluation of the Environmental Bias on Accelerometer-Measured Total Daily Activity Counts and Owner Survey Responses in Dogs with Osteoarthritis.

Objective To determine if environmental variables affect the average daily activity counts (AC) of dogs with osteoarthritis (OA) and/or owners' perception of their dog's clinical signs or quality of life. Methods The AC and Canine Brief Pain Inventory (CBPI) owner questionnaires of 62 dogs with OA were compared with daily environmental variables including the following: average temperature (°C), high temperature (°C), low temperature (°C), relative humidity (%), total precipitation (mm), average barometric pressure (hPa) and total daylight hours. Results Daily AC significantly correlated with average temperature and total daylight hours, but average temperature and total daylight hours accounted for less than 1% of variation in AC. No other significant relationships were found between daily AC and daily high temperature, low temperature, relative humidity, total precipitation or average barometric pressure. No statistical relationship was found between daily AC and the CBPI, nor between environmental variables and the CBPI. Canine Brief Pain Inventory scores for pain severity and pain interference decreased significantly over the test period. Clinical Significance The relationship between daily AC and average temperature and total daylight hours was significant, but unlikely to be clinically significant. Thus, environmental variables do not appear to have a clinically relevant bias on AC or owner CBPI questionnaires. The decrease over time in CBPI pain severity and pain interference values suggests owners completing the CBPI in this study were influenced by a caregiver placebo effect.