The concentration of toluene in the building exhaust was 120 µg m-3, more than double the highest level measured indoors, suggesting a possible toluene source in the restrooms. The cleaning compound 2-butoxyethanol was slightly higher indoors, but at very low concentrations.The compounds listed in this category have many sources, including outdoor air. For the most part there was little difference across the building spaces for these compounds, and little difference from the ambient air measurement. The single exception to this observation is methylene chloride that appears to increase by about a factor of ten indoors. It is possible that this compound is in use as a cleaning solvent, or it may be present in computer equipment or other supplies. Methylene chloride is also used as a spot remover in dry cleaning processes and may be carried into the building on occupant clothing. The levels of this compound were low relative to health standards . Note that for compounds where measurements were below the LOQ the relative difference may be an artifact of imprecision of measurement rather than a reflection of real differences. These values should be interpreted carefully.
In Table 4 the compounds which display relative reductions between two zones are shaded a tan color,growing tomatoes hydroponically while those with relative increase of factors of tens are shaded light green, and those with relative increases by factors of 100 are shaded red. The HVAC inlet to the building which includes an air washer and filtration showed a reduction of all measured VOCs and aldehydes with the exception of octanal, 1,4‐ dichlorobenze, decamethylpentasiloxane, phenol, TXIB and diethylpthalate. The reductions were ranged from 4% to 100% for 2‐butoxyethanol, d‐ limonene, trichloroethylene, and a‐pinene. The plasticizer concentrations increased140% and 320% as the air moved from outside into the greenhouse. VOC concentrations all increased as the air was transmitted through the greenhouse. The concentration of the odorous compounds hexanal and nonanal increased by 68% and 110%, respectively in the greenhouse. Most other compounds showed modest increases on the order of 10s of percentage points, although styrene concentrations increased by almost a factor of 7 in the greenhouse. With only a few exceptions , VOC and aldehyde concentrations increased as the ventilation air moved from the greenhouse into the occupied building spaces. Increases between the average indoor concentrations and the greenhouse air exit ranged from 6% for toluene to a factor of 120 for the cleaning solvent 2‐butoxyethanol. The cleaning solvent d‐limonene increased by a factor of 56, methylene chloride increased by a factor of 11, and a‐pinene by a factor of 64.Diethylpthalate increased by a factor of 21.
Odorous compounds hexanal, nonanal, and octanal all increased by factors of two to four, as did the irritating and carcinogenic compound formaldehyde. The deodorant 1,4‐dichlorobenzene concentration increased by over a factor of six. The concentration of the VOCs and aldehydes in the HVAC exhaust stream was in only a single case lower than the incoming air , where it was zero in the exhaust. D‐limonene was 19 fold higher in the exhaust than the intake, 1,4‐ dichlorobenzen was 76 fold higher, and diethylpthalate increased 17 fold. Concentrations in the exhaust vs. greenhouse tended to be higher than the comparison to the ambient air – this is due the observed decrease at the intake relative to the greenhouse – possibly the benefit of the air washer. Overall, exhaust concentrations exceeded that supplied to the zones containing plants by small to large multiples. The concept that the building air is scrubbed clean of gaseous air contaminants by the plants is not supported by the data. This being said, it is not known what the building IAQ would be without the plants. Table 5 provides a comparison between the measured indoor VOC and aldehyde concentrations in the PBC and those measured in a survey of office buildings in the United States . From 1994 to 1998 the U.S. Environmental Protection Agency conducted the Building Assessment and Survey Evaluation Study of 100 randomly selected office buildings in the continental U.S. . The data in Table 5 are summary statistics of measurements taken from the BASE study . Note that not all of the VOCs measured in the PBC were studied in the BASE study, and vise‐versa. The BASE study did not measure all of the listed compounds in all 100 buildings as can be seen from the Table. Compounds for which the PBC had more that a factor of two greater indoor concentrations than the BASE Study mean are 1,4‐dichlorobenzene, methylene chloride , and TXIB.
The measured PBC formaldehyde and acetaldehyde levels were both above the mean BASE Study levels by more than one standard deviation. Compounds for which the PBC had one half or less of the concentration of the BASE Study indoor concentrations included 2‐butoxyethanol, acetone, d‐limonene, phenol, and styrene. Both 2‐butoxyethanol and d‐limonene are cleaning agents that may be used less frequently in the PBC than in the U.S. office buildings. The compound measured that is of greatest concern is formaldehyde, as discussed above, which has an 8‐hr average REL of 9 µg m‐3. The average across the measured spaces in Floors 5 and 3 was 28±1.4 µg m‐3. However, the observed formaldehyde concentrations fall within levels that have been recorded in U.S. office buildings . The observed levels of odorous compounds hexanal, nonanal, and octanal may detract from perceived air quality in the PBC, as the observed concentrations exceed document odor thresholds. However the levels may not be high enough to be irritating to occupants. The presence of 1,4‐dichlorobenzene in the ambient and greenhouse air suggests that some short circuiting of ventilation exhaust back into the building. It may also be possible that some leakage across the heat recovery wheel is slightly contaminating the fresh intake air. The removal of ambient particulate matter by the PBC rooftop air handler, the particle loss mechanisms in the air transit through greenhouse and ducting into the building, and the re‐circulating filtration of air by the floor level AHUs appears to be rather successful. Indoor PM2.5 was reduced to 26±8 µg m-3 7% of outdoor levels. There are no indoor standards for PM2.5, but the World Health Organization has set the outdoor 24 hour standards at 25 µg/m3, and the annual PM2.5 standard at 10 µg/m3 . Considering the extremely high outdoor PM2.5 levels in New Delhi, the protective environment provided by the PBC is phenomenal. This one‐day study did not measure all possible air contaminants in the PBC or surrounding outdoor air. Ozone is an important air contaminant that was not measured, that may have a bearing on IAQ in the building. On January 1 the ozone level in the ambient air was likely around it’s lowest for the year as its formation is dependent on radiation from the sun, and it varies with the seasons. However, during other times of the year, ozone entrained into the building could have a significant impact on IAQ as it reacts with d‐limonene, a‐pinene, and other alkene compounds. Future work should include a study of ozone entry into the building. Rose production is currently the largest component of California’s $300 million cut-flower industry. In 2001, California growers produced 66% of the U.S. rose crop, with a wholesale value of $45 million . The key pests of cut roses are two spotted spider mites , western flower thrips and rose powdery mildew . The two spotted spider mite is a foliage feeder that extracts the cell contents from leaves. This feeding causes foliar stippling and can disrupt the plant’s photosynthetic and water balance mechanisms . The western flower thrips is both a foliage and flower feeder, although it feeds primarily on flowers in the cut-rose system . Powdery mildew is probably the most widespread and best-known disease of roses. The fungus produces a white, powdery-appearing growth of mycelium and conidia on leaves,hydroponic growing supplies which can cause distortion, discoloration and premature senescence. Although it causes some disruption of photosynthesis and transpiration control, the key impact of powdery mildew is reduced aesthetic value caused by the white, powdery spots and leaf distortion. Fresh cut roses are often harvested twice daily, so revised reentry intervals imposed by the U.S. Environmental Protection Agency after pesticide application limit the number of pesticides that are useful in this production system .
In addition, the typical number of pesticide sprays applied to roses grown for cut flowers has impeded the implementation of integrated pest management procedures, particularly the use of biological controls. The IPM approach to pest management incorporates all cost-effective control tactics appropriate for the crop, including biological, cultural and chemical controls. Pesticides that target hard-to-kill floriculture pests frequently kill natural enemies as well, which favors continued reliance on conventional pesticides while discouraging the adoption of biological control. Heavy pesticide use against key pests in the greenhouse has resulted in the widespread development of pesticide resistance in western flower thrips , mites , white flies , aphids and leaf miners . The heavy use of pesticides in cut roses is also a worker safety concern in global and local production. California rose growers reached a crisis point about 8 years ago, when pesticide resistance, costs and limited pesticide availability threatened the growers’ ability to effectively manage two spotted spider mites. At the same time, a new cut-rose production system that favors the success of IPM was gaining widespread acceptance. Roses were traditionally grown in soil with a hedgerow training system, where flowers are cut in a manner that gradually creates a 7-foot or taller hedge. The hedges are pruned back annually to about a 3-foot height and the process is begun again. With the new bent-shoot method, plants are grown in raised containers in a modified hydroponics system. Most of the shoots are bent downward at the crown to intercept more light, creating a perennial lower canopy that exists for the 5 to 8 years of crop production. The upper canopy contains only stems that produce flowers, which take 45 to 52 days to develop. The bent-shoot method creates a spatial separation between the harvested flowers and perennial foliage that does not exist in standard roses. Pesticides to control western flower thrips and powdery mildew that are more compatible with mite predators have also recently become available. These developments, coupled with the difficulty that rose growers were facing in controlling spider mites, made us confident that we could develop a successful IPM program that rose growers would adopt. This project was initiated in 2000 with major funding from the Pest Management Alliance Program of the California Department of Pesticide Regulation and was later supplemented with additional funding. The goal of the Alliance project was to foster a team approach to the development and implementation of IPM programs in a given commodity and to document a reduction in traditional pesticide use. Our Alliance team included researchers, county-based advisors, growers, chemical and biological-control industry representatives, commodity associations and government officials. Our objective was to develop a cost-effective IPM program for the key pests of cut roses that included sampling, thresholds, biological control and directed sprays of reduced-risk pesticides.Eight growers spanning the major rose-producing areas of California participated in the program. Each grower contributed an IPM and a conventional-practice greenhouse; all greenhouses were between 5,000 and 10,000 square feet in size. All pest management decisions in the IPM greenhouses were based on the IPM program that we developed, while the grower made all pest management decisions in the conventional greenhouses. Data was collected and compared on a weekly basis by trained scouts using a comprehensive sampling plan that provided information about the density of insects, mites and diseases. The project included growers with several different rose varieties and both the bent-cane and hedgerow training techniques, but we kept these two variables standardized within a location. Implementation began in March 2000 and continued until January 2001. Fixed precision sampling plans that had been previously developed for two spotted spider mites and western flower thrips were used in our scouting program. This type of sampling plan was developed through intensive surveys of a crop to determine a pest’s spatial distribution. The degree of acceptable error was decided upon in advance, and the number of samples needed to obtain that precision was calculated using knowledge of the pest’s spatial distribution in the crop.