1 00:00:01,120 --> 00:00:02,400 VO: Welcome to the tutorial... 2 00:00:02,520 --> 00:00:07,680 for using ConsExpo Web's 'emission from solid materials' model... 3 00:00:07,800 --> 00:00:12,520 to estimate the inhalation of substances evaporating from solid materials... 4 00:00:12,640 --> 00:00:15,080 in an indoor environment. 5 00:00:15,920 --> 00:00:21,120 The tutorial includes an introduction, a description of the model concept... 6 00:00:21,240 --> 00:00:23,440 descriptions of the input fields... 7 00:00:23,560 --> 00:00:28,560 for which the user needs to insert values that fit the exposure scenario... 8 00:00:28,680 --> 00:00:33,080 and a demonstration on how to interpret the model outcomes. 9 00:00:33,800 --> 00:00:37,880 The 'emission from solid materials' is one of the inhalation exposure models... 10 00:00:38,000 --> 00:00:41,080 that ConsExpo Web has to offer. 11 00:00:41,840 --> 00:00:44,720 It is most suitable for consumer exposure scenarios... 12 00:00:44,840 --> 00:00:47,960 for volatile or semi-volatile substances... 13 00:00:48,080 --> 00:00:52,760 that are slowly released from solid materials in an indoor environment... 14 00:00:52,880 --> 00:00:58,480 such as furniture, floors, walls or objects. 15 00:00:58,600 --> 00:01:01,640 'Emission from solid materials' can be selected... 16 00:01:01,760 --> 00:01:08,080 in the model dropdown menu at ConsExpo Webs 'inhalation' tab. 17 00:01:08,640 --> 00:01:12,680 The consumer is assumed to reside in the room with the solid material... 18 00:01:12,800 --> 00:01:16,960 from which substances are emitted for a prolonged period of time... 19 00:01:17,080 --> 00:01:23,120 leading to a long term exposure duration of days, months or even years. 20 00:01:23,760 --> 00:01:27,800 The 'emission from solid materials' model consists of three stages... 21 00:01:27,920 --> 00:01:33,000 that simulate the diffusion of the substance in the solid material matrix... 22 00:01:33,120 --> 00:01:36,800 the partitioning behaviour at the interface of the material surface... 23 00:01:36,920 --> 00:01:39,160 and a stagnant layer of air... 24 00:01:39,280 --> 00:01:44,080 and the mass transfer of substance from the stagnant air to the room air. 25 00:01:44,720 --> 00:01:48,960 The following animation visualizes the fate of the evaluated substance... 26 00:01:49,080 --> 00:01:52,160 expressed here as purple dots. 27 00:01:52,280 --> 00:01:54,000 Inside the solid material... 28 00:01:54,120 --> 00:01:59,240 the substance moves in randomly directed patterns driven by diffusion. 29 00:01:59,360 --> 00:02:03,280 Once the substance hits the interface with the stagnant layer of air... 30 00:02:03,400 --> 00:02:06,400 it can leave the solid material. 31 00:02:06,520 --> 00:02:09,680 Here the substance is driven by partitioning behaviour... 32 00:02:09,800 --> 00:02:12,440 searching for thermodynamic equilibrium... 33 00:02:12,560 --> 00:02:16,800 between the concentration in stagnant air and the material. 34 00:02:16,920 --> 00:02:21,520 As such, the substance may travel back into the material. 35 00:02:21,640 --> 00:02:26,400 Finally, the substance mass is transferred from the stagnant air... 36 00:02:26,520 --> 00:02:31,960 into the room air in which the inhalation exposure scenario takes place. 37 00:02:32,640 --> 00:02:35,120 Here, the input fields are described... 38 00:02:35,240 --> 00:02:38,920 so that the model user knows how to insert appropriate values... 39 00:02:39,040 --> 00:02:42,600 fit for the consumer exposure scenario. 40 00:02:42,720 --> 00:02:46,760 'The product surface area' refers to the area of the product material... 41 00:02:46,880 --> 00:02:49,600 that is in contact with air. 42 00:02:49,720 --> 00:02:53,880 The unit varies from square centimetres for small objects... 43 00:02:54,000 --> 00:02:58,480 to square meters for large surfaces, such as floors or walls. 44 00:02:59,320 --> 00:03:04,240 The 'product thickness' describes how thick the layer of the product material is... 45 00:03:04,360 --> 00:03:07,320 in which the substance is formulated. 46 00:03:07,440 --> 00:03:09,000 It may range, for example... 47 00:03:09,120 --> 00:03:12,800 from micrometres in the case of a layer of dried paint... 48 00:03:12,920 --> 00:03:14,800 millimetres for a piece of paper... 49 00:03:14,920 --> 00:03:18,720 or centimetres for wooden boards or window panes. 50 00:03:19,560 --> 00:03:23,720 The 'product density' refers to the density of the product material... 51 00:03:23,840 --> 00:03:27,760 in which the substance of interest is formulated. 52 00:03:27,880 --> 00:03:31,480 It is expressed as a unit of mass per unit of volume... 53 00:03:31,600 --> 00:03:37,000 such as grams per cubic centimetre or kilograms per litre. 54 00:03:37,120 --> 00:03:39,920 The diffusion coefficient is an input parameter... 55 00:03:40,040 --> 00:03:43,960 that describes how fast the evaluated substance diffuses... 56 00:03:44,080 --> 00:03:46,560 within the product material. 57 00:03:46,680 --> 00:03:49,720 As such, it depends on the properties of the substances... 58 00:03:49,840 --> 00:03:53,520 as well as the product material. 59 00:03:53,640 --> 00:03:55,680 The faster a substance diffuses... 60 00:03:55,800 --> 00:03:59,560 the less time it will take before it reaches the interfacial area... 61 00:03:59,680 --> 00:04:04,760 from which it can evaporate into the stagnant air above the material. 62 00:04:04,880 --> 00:04:09,000 Consequentially, substances with high diffusion coefficients... 63 00:04:09,120 --> 00:04:12,000 are more prone to rapid evaporation. 64 00:04:12,120 --> 00:04:15,600 Collecting the accurate data for the diffusion coefficient... 65 00:04:15,720 --> 00:04:17,720 can be a challenging task... 66 00:04:17,840 --> 00:04:22,600 because diffusion coefficients may vary within orders of magnitude... 67 00:04:22,720 --> 00:04:26,880 between substances and between product materials. 68 00:04:27,440 --> 00:04:29,360 The unit for diffusion coefficient... 69 00:04:29,480 --> 00:04:34,040 is expressed as the squared distance per unit of time... 70 00:04:34,160 --> 00:04:38,480 and is typically referred to as square meter per second. 71 00:04:38,600 --> 00:04:40,920 The input field 'weight fraction'... 72 00:04:41,040 --> 00:04:44,720 refers to the amount of substance formulated in the product... 73 00:04:44,840 --> 00:04:47,080 per unit of product amount. 74 00:04:47,200 --> 00:04:50,720 Here, the product amount is the sum of the substance mass... 75 00:04:50,840 --> 00:04:54,720 and the mass of the material it is formulated in. 76 00:04:54,840 --> 00:04:56,960 Typically weight fraction is unitless... 77 00:04:57,080 --> 00:05:00,360 because it refers to the amount of substance in grams... 78 00:05:00,480 --> 00:05:03,520 divided by the amount of product in grams... 79 00:05:03,640 --> 00:05:07,840 but it can also be inserted as a weight percentage. 80 00:05:08,600 --> 00:05:11,080 The product-air partition coefficient... 81 00:05:11,200 --> 00:05:15,880 refers to the ratio of the substance concentration in the product material... 82 00:05:16,000 --> 00:05:19,280 to the substance concentration of the product in air... 83 00:05:19,400 --> 00:05:22,560 at thermodynamic equilibrium. 84 00:05:22,680 --> 00:05:26,600 Typically, partitioning coefficients are symbolized by the letter K... 85 00:05:26,720 --> 00:05:29,800 and by the two media between the substances partitions... 86 00:05:29,920 --> 00:05:32,840 expressed in subscript. 87 00:05:32,960 --> 00:05:35,200 The partitioning coefficients don't depend... 88 00:05:35,320 --> 00:05:38,640 on the initial concentration of the substance in the product... 89 00:05:38,760 --> 00:05:43,400 because it refers to a state of thermodynamic equilibrium. 90 00:05:43,520 --> 00:05:47,320 Substances with low product-air partitioning coefficients... 91 00:05:47,440 --> 00:05:50,160 have little tendency to remain in the product... 92 00:05:50,280 --> 00:05:54,640 and are as such driven to equilibrium at the air side. 93 00:05:54,760 --> 00:05:58,920 As a consequence, these substances are more prone to rapid evaporation... 94 00:05:59,040 --> 00:06:02,280 from the solid product material. 95 00:06:02,400 --> 00:06:04,960 Just as with diffusion coefficients... 96 00:06:05,080 --> 00:06:09,440 collecting accurate data for the product-air partitioning coefficient... 97 00:06:09,560 --> 00:06:11,840 can be a challenging task... 98 00:06:11,960 --> 00:06:14,680 because it may vary within orders of magnitude... 99 00:06:14,800 --> 00:06:19,640 between substances and between product materials. 100 00:06:19,760 --> 00:06:24,120 The unit of the partitioning coefficient can be inserted as linear... 101 00:06:24,240 --> 00:06:26,040 but also as loglinear... 102 00:06:26,160 --> 00:06:32,160 because the concentrations across the two media can vary within orders of magnitude. 103 00:06:32,800 --> 00:06:35,240 The emission from solid materials model... 104 00:06:35,360 --> 00:06:41,600 is designed to simulate exposure scenarios over a long period of the time. 105 00:06:41,720 --> 00:06:46,040 As such, the exposure dose of the substance inhaled by the consumer... 106 00:06:46,160 --> 00:06:50,160 does not only depend on the concentration of the substance in the room air... 107 00:06:50,280 --> 00:06:55,400 but also on the timeframe in which the consumer is present in the room. 108 00:06:55,520 --> 00:06:57,160 Some consumer products... 109 00:06:57,280 --> 00:07:00,600 such as, for example, flooring agents and drain openers... 110 00:07:00,720 --> 00:07:04,880 advise that a period of time should elapse before entering the room... 111 00:07:05,000 --> 00:07:08,080 after the product has been applied. 112 00:07:08,200 --> 00:07:11,600 This timeframe can be inserted in ConsExpo Web... 113 00:07:11,720 --> 00:07:17,600 using the 'start exposure' and 'exposure duration' input fields. 114 00:07:17,720 --> 00:07:21,360 The start exposure input field refers to the amount of time... 115 00:07:21,480 --> 00:07:25,760 between application of the product and entering the room. 116 00:07:26,520 --> 00:07:33,000 'Exposure duration' refers to the amount of time the consumer then stays in the room. 117 00:07:33,120 --> 00:07:37,440 The intensity of the exposure is calculated in ConsExpo... 118 00:07:37,560 --> 00:07:40,600 as the air concentration in the room over time... 119 00:07:40,720 --> 00:07:44,320 for which graphs and data tables are available. 120 00:07:44,440 --> 00:07:48,840 Here, it can be seen that the air concentration changes over time... 121 00:07:48,960 --> 00:07:51,440 so that the inhaled dose depends on the moments... 122 00:07:51,560 --> 00:07:55,680 the consumer enters and leaves the room. 123 00:07:55,800 --> 00:07:59,400 This is to be inserted as 'start exposure'... 124 00:07:59,520 --> 00:08:03,280 and the period of the time in which the consumer then stays in the room... 125 00:08:03,400 --> 00:08:08,120 is to be inserted as 'exposure duration'. 126 00:08:08,240 --> 00:08:11,400 The mass transfer coefficient expresses the velocity... 127 00:08:11,520 --> 00:08:15,600 at which the substance in the stagnant layer of air above the product... 128 00:08:15,720 --> 00:08:17,880 is transferred to the room air. 129 00:08:18,000 --> 00:08:20,920 Such transfer depends on a number of factors... 130 00:08:21,040 --> 00:08:25,600 such as the substance's molecular weight, the air flow over the product... 131 00:08:25,720 --> 00:08:28,160 and the surface roughness of the product. 132 00:08:28,280 --> 00:08:31,040 The most recent ConsExpo Web fact sheets... 133 00:08:31,160 --> 00:08:36,760 suggest a default value for the mass transfer coefficient of 10 meters per hour. 134 00:08:37,560 --> 00:08:42,720 The 'emission from solid materials' model also includes 'room volume'... 135 00:08:42,840 --> 00:08:47,440 'ventilation rate', 'inhalation rate' as input fields... 136 00:08:47,560 --> 00:08:52,640 and the 'absorption' model to calculate internal exposure doses. 137 00:08:52,760 --> 00:08:55,200 These are not explained in this tutorial... 138 00:08:55,320 --> 00:08:59,920 but are covered in the 'introduction to inhalation models tutorial'... 139 00:09:00,040 --> 00:09:06,400 which explains the input fields and models that are common to all inhalation models. 140 00:09:07,320 --> 00:09:11,520 We would like to acknowledge all partners in the ConsExpo project: 141 00:09:11,640 --> 00:09:13,280 Health Canada... 142 00:09:13,400 --> 00:09:19,120 the French Agency for Food, Environmental and Occupational Health and Safety... 143 00:09:19,240 --> 00:09:22,840 the German Federal Institute for Risk Assessment... 144 00:09:22,960 --> 00:09:26,320 the Swiss Federal Office of Public Health... 145 00:09:26,440 --> 00:09:30,400 the Netherlands Food and Consumer Product Safety Authority... 146 00:09:30,520 --> 00:09:34,520 and the Dutch Ministry of Health, Welfare and Sport. 147 00:09:34,640 --> 00:09:36,960 (SILENCE)