Human Health Risk Assessment for Priority Substances

Appendix A - Reference Values for Assessing Total Daily Intake of Priority Substances by the General Population in Canada

The general principles and recommended values for body weights, inhalation of indoor and outdoor air, consumption of drinking water, foodstuffs and soil, and use of consumer products in the calculation of total daily intake of Priority Substances by the general population in Canada⁸ are presented in this Appendix. These values are recommended to provide consistency in approach; however, the need for the application of sound scientific judgement on a case-by-case basis is fundamental to the estimation of exposure for assessment of "toxic" under paragraph 11(c) of CEPA.

1.0 Age

Exposure to environmental substances may change substantially over the course of an individual's lifetime, as a result of variations in medium-specific intakes, activities and physical attributes with age. Consequently, exposure of the general population of Canada is estimated for several defined periods of life: for infants (0-6 months), pre-school children (7 months-4 years), elementary school children (5-11 years), teenagers (12-19 years), and adults (20 years of age and older). These categories are intended to reflect more-or-less discrete stages of life in terms of varying potential for exposure to environmental substances. Hence, the period up to 6 months of age is when many infants may be exposed to substances present in breast milk. Also, preschoolers' exposure to contaminants in soil may be significantly higher than that for other age groups. Children of all ages have relatively high intakes of food per unit of body weight. Adulthood is a period of long-term lower-level exposure via most environmental media, with relatively high potential exposure to some substances through activities such as the use of consumer products.

2.0 Body Weights

Estimates of body weights presented in Table 1 are based on the most recent Canadian surveys; available data indicate that body weights have increased since earlier surveys. The body weights for teenagers and adults are taken from the 1981 Canada Fitness Survey of 16,000 individuals, while those of infants, pre-schoolers and grade school children are derived from the 1970-1972 Nutrition Canada survey of over 13,000 individuals (EHD, 1992).

3.0 Inhalation of Indoor and Outdoor Air

Since there are no quantitative data on amounts of air inhaled by Canadians in a range of age groups, the recommended age-specific intakes presented in Table 1 for school-age children and adults are the weighted means of the values calculated by the Environmental Health Directorate Working Group on Reference Values (EHD, 1992). These values were derived from estimates contained in the International Commission on Radiological Protection (ICRP) report of the Task Group on Reference Man (ICRP, 1975), corrected for the difference in height between the average Canadian and the ICRP Reference Man [using the formulae in the Intermountain Thoracic Society Manual (Morris et al., 1984)]. When data on concentrations of a substance in both indoor and outdoor air are available, it is assumed that intake of indoor and outdoor air are in proportion to the average amount of time spent indoors (approximately 20 hours) and outdoors each day [4 hours, divided evenly between time spent out of doors and in a motor vehicle, if data on concentrations in the latter case are available] (U.S. EPA, 1985).

4.0 Consumption of Drinking Water

The recommended values for the ingestion of drinking water presented in Table 1 are based primarily on the 1977-1978 survey of Canadian tap water consumption conducted by the Environmental Health Directorate of the Department of National Health and Welfare (NHW, 1981). This survey was conducted utilizing questionnaires and individual water consumption diaries of 970 people from 295 households. Distribution of the selected subjects was based on a representative sample of the Canadian population. The results of a similar survey from the United Kingdom (Hopkin and Ellis, 1980) have been used to distinguish the daily tap water consumption for persons aged from 6 to 17 years of age in the EHD survey into the 5-to-11- and 12-to-19-year age classes.

There are no data available on the consumption of drinking water by Canadian infants. It has been assumed, therefore, that infants are exclusively breast-fed and do not consume drinking water (exclusively breast-fed children do not require supplementary liquids). In the absence of data on the levels of a chemical substance in breast milk, or if the consumption of food or drinking water appear to be more important routes of exposure, it is assumed that infants are exclusively formula-fed for the first 6 months of life, consuming an average 0.75 litres/day. This estimate is based on the use of drinking water in the preparation of powdered infant formulae for exclusively formula-fed infants, discussed in the next section. For infants consuming other foods (see section 5.0 of this Appendix), the recommended intake of drinking water is 0.75 litres/day; if data on the concentration of chemical substances in foods include tap water added to beverages (i.e., the concentrations represented those in "table-ready" beverages), the volume consumed as drinking water (0.2 litres) reported for this age class in the U.S. Nationwide Food Consumption Survey (NCI, 1989) is used in the assessment of total daily intake.

5.0 Consumption of Food

The estimates of food consumption are based on the Nutrition Canada Survey (NCS)[NHW, 1977], conducted between 1970 and 1972, which involved detailed dietary surveys of over 13,000 Canadians, based on the 24-hour recall method. Data on food consumption for the recommended age classes represent the general food groups used in the NCS Food Consumption Patterns Report (Table 2), and the individual composites compiled by staff of the Food Directorate of the Department of National Health and Welfare (Table 3). The NCS is now approximately 20 years old, and there have been significant changes in the types of foods consumed by Canadians. Most notable among these are reductions in the consumption of eggs and whole milk, and increases in the amounts of poultry, fish and low-fat milk consumed (Caputo and Poutanen, 1990). Any errors introduced by these changes in these dietary intakes are likely to be relatively small in relation to other uncertainties associated with estimating the average total daily intake of Priority Substances by the general population.

Where available data on the level of substances do not correspond exactly to those for which consumption data are presented in Tables 2 and 3, it may be necessary to assume that data for a limited number of individual food items apply to the broad food groups presented in Table 2, or to consider (as a minimum estimate) intakes only from the foodstuffs for which monitoring data are available. The approach which is taken is based on professional judgement concerning the likely distribution of chemical substances among various foodstuffs and is dependent upon factors such as use patterns of the substance, or its partitioning among food component groups (e.g., fats).

Information on various components may be useful in assessing the intake of chemical substances from foods; the intake of lipophilic chemicals may be derived from information on the fat content and consumption of food products. The composition of a large number of Canadian foods has been compiled in the report "Nutrient Value of Some Common Foods" (NHW, 1988), and the intakes of fat, calories, protein, etc. by various age classes are presented in the NCS "Food Consumption Patterns Report" (NHW, 1977).

In Canada, infant feeding practices have changed dramatically over the last 30 years (Tanaka et al., 1987; NHW, 1990). Recent studies indicate that a majority of Canadian mothers breast-feed; breast-feeding initiation rates are close to 80%, with 30% still breast-feeding their infants after 6 months. The intake of breast milk peaks between 4 to 6 months of age. Solid foods are introduced to approximately 50% of infants by 4 months of age, and 89.5% by 6 months of age. To reflect these practices, estimation of total daily intake is generally based on the assumption that a typical infant is exclusively breast-fed up to 6 months of age, after which foods are consumed in the quantities determined in the NCS. No Canadian data on the volume of breast milk consumed have been identified, but the average intake of breast milk over this period has been estimated to be 0.75 litres/day (or kg/day), based on studies of well-nourished mothers in Sweden and the United States (NHW, 1983); this intake is similar to that reported in a number of other studies of exclusively breast-fed infants (Butte et al., 1991, and references therein).

In the absence of data on the concentration of a substance in breast milk, or where other food types are a more important source of exposure to a substance, it is assumed that infants are exclusively formula-fed for the first 6 months of life and consume on average the same volume as breast-fed infants (i.e., 0.75 litres/day). (Comparative studies indicate that bottle-fed infants consume similar or slightly higher volumes than breast-fed infants). Alternatively, in those cases in which table foods appear to be an important source of exposure to a chemical substance, the food intakes for infants compiled through the NCS may be used (Tables 2, 3, and Table 2.1 in NHW, 1977). At the time at which this survey was conducted, solid foods were generally introduced to infants' diets at a much earlier age than at present; hence, the food intakes from the NCS likely overestimate the current consumption of solid foods by infants.

6.0 Ingestion of Soil

The intake of soil by the various age groups of the population of Canada presented in Table 1 are based on recent studies from the United States and the Netherlands, in which tracer elements have been used to estimate the amount of soil ingested (Binder et al., 1986; Clausing et al., 1987; Calabrese et al., 1989; van Wijnen et al., 1990).

7.0 Consumer Products

In most cases, direct exposure to Priority Substances from consumer products is not estimated. However, such products generally contribute to concentrations in indoor air for which information is often included in estimates of total daily intake.

Exceptionally, however, estimates of intake from consumer products may be calculated. In view of the diverse range of consumer products and applications, exposure to chemical substances present in consumer products is estimated on the basis of plausible upper bound assumptions regarding the intensity, frequency and duration of exposure. Data and approaches for estimating exposures from consumer products (e.g., exposure to volatile organic compounds while filling a gas tank) have been reported by the U.S. EPA (1987a, 1987b, 1987c) and Wallace et al. (Wallace, 1986; Wallace et al., 1986, 1987, 1988, 1989).

Table 1

Recommended Values For Body Weight And Intakes Of Air, Water And Soil By Average Canadians

Age (yr)	Body Weight1 (kg)	Air Intake2 (m 3 /d)	Water Intake3 (L/d)	Soil Intake4 (mg/d)
0-6 mo	7	2	BF-0/0 NBF-0.2/0.75	35
7 mo-4	13	5	0.2/0.8	50
5-11	27	12	0.3/0.9	35
12-19	57	21	0.5/1.3	20
20+	70	23	0.4/1.5	20

1. For infants, pre-school children and elementary school children, weighted average from Nutrition Canada Survey; for teenagers and adults, weighted average from Canada Fitness Survey (data taken from EHD, 1992; average for adults is 69 kg, but traditionally 70 kg has been used).
2. For infants, estimated from linear regression between values of 0.8 m³ (newborn) and 3.8 m³ (1-year-old) from ICRP (1975), estimate at 0.25 years (mid-range); for pre-schoolers, from linear regression between 3.8 m³ [1-year-old] (ICRP, 1975) and 9.25 m³ [7-year-old, both sexes] (EHD, 1992), estimate at 2.25 years (mid-range); other values are weighted average from EHD (1992), based on sample sizes from Canada Fitness Survey for 7-11-year-olds, 12-19-year-olds, and adults.
3. Water intakes presented separately as tapwater/tapwater+tapwater-based beverages (water, tea, coffee, reconstituted soft drinks); exclusively breast-fed infants (BF) do not require supplementary liquids (NHW, 1983); estimates for non-breast-fed infants (NBF) are based on NCI (1989) for volume consumed as drinking water, and on consumption of 750 mL/day of formula made from powdered formula and tap water for total drinking water (see text for discussion); for pre-schoolers, weighted mean of < 3 and 3-5-year classes from NHW (1981); for elementary school children and teenagers, from NHW (1981) for 6-17-year class (0.3/1.1 L/d), adjusted by ratio of consumption for 5-11 years (0.54 L/d) and 12-17 years (0.77 L/d) to mid-range (0.66 L/d) from Hopkin and Ellis (1980); for adults, mean of persons 18 and over from NHW (1981).
4. For infants, value from van Wijnen et al. (1990) for children less than 1 year, for pre-schoolers, average of 4 estimates of soil intake by 1-4-year-olds (Binder et al., 1986; Clausing et al., 1987; Calabrese et al., 1989; van Wijnen et al., 1990); for teenagers, assume same intake as for adults; estimate for adults from EHD (1992); estimate for 5-11-year-olds is midpoint between 1-4-year-olds and adults.

Table 2

Mean Consumption Of Various Food Groups By Canadians, From Nutrition Canada Survey

Food Group	Composite1	Consumption (g/person/d)
		0 - 6 mo2	7 mo - 4 yr	5 - 11 yr	12 - 19 yr	20+ yr
Dairy Products	1-10	545	670	609	573	283
Meat, Poultry, Fish, Eggs	12-27, 110	37	90	120	169	183
Cereal Products	32-50, 107	53	168	300	325	247
Fruit And Fruit Products	74-91, 109	112	189	202	160	186
Vegetables	51-73, 112	42	125	198	250	250
Fats	11, 92, 93	0.8	11	21	29	25
Nuts And Dried Legumes	94, 108	0.2	6	13	19	12
Food, Primarily Sugar	95-101, 111	25	46	57	67	57
Mixed Dishes And Soups	28-31	5	71	82	89	100
Soft Drinks, Alcohol	104-106	2	102	196	264	255
Sample Size		132	1,199	2,086	2,342	7,037

1. Derived from table of consumption of individual food composites (Table 3).
2. These data will be used if it is assumed that the infant is not exclusively breast-fed or not exclusively formula-fed (see text for discussion).

Table 3

Mean Consumption Of Individual Food Composites By Canadians, From Nutrition Canada Survey

Food Composite		Consumption (g/person/day)
		0-6 mo1	7 mo-4 yr	5-11 yr	12-19 yr	20+ yr
1.	Milk, Whole	274.162	377.88	323.16	255.65	138.24
2.	Milk, 2%	188.60	194.50	185.61	194.75	60.64
3.	Milk, Skim	21.20	59.67	55.57	72.56	30.83
4.	Evaporated Milk, Canned	59.78	12.04	6.54	7.06	11.46
5.	Cream, 10-12% Butter Fat	0.00	1.63	2.83	2.65	10.19
6.	Ice Cream	1.37	15.35	25.59	25.78	12.80
7.	Yogurt	0.00	0.78	0.48	0.87	1.54
8.	Cheese	0.11	2.56	3.18	5.66	8.33
9.	Cheese, Cottage	0.00	1.73	1.33	1.74	5.35
10.	Cheese, Processed Cheddar	0.06	3.59	4.92	6.43	3.81
11.	Butter	0.73	7.06	12.94	16.67	13.61
12.	Beef, Steak	0.07	3.09	7.37	10.89	17.38
13.	Beef, Roast And Stewing	0.27	6.49	12.21	23.27	27.00
14.	Beef, Hamburg	31.36	20.05	19.23	30.84	21.61
15.	Pork, Fresh	0.00	7.24	11.98	22.74	22.73
16.	Pork, Cured	0.00	1.95	3.96	4.40	7.78
17.	Veal	0.00	0.50	0.33	1.79	2.16
18.	Lamb	0.00	0.03	1.80	1.20	0.78
19.	Poultry, Chicken And Turkey	0.00	13.24	16.72	20.32	21.17
20.	Eggs	4.67	24.16	21.05	21.50	32.29
21.	Organ Meats, Liver, Kidney	0.00	0.91	1.85	2.27	2.81
22.	Cold Cuts And Luncheon Meats	0.00	5.72	7.85	11.27	9.27
23.	Luncheon Meats, Canned	0.00	0.88	0.97	2.20	2.10
24.	Fish, Marine, Fresh Or Frozen	0.50	1.52	4.81	5.00	6.59
25.	Fish, Fresh Water, Fresh Or Frozen	0.00	1.12	1.08	1.09	1.26
26.	Fish, Canned	0.00	0.43	1.84	4.13	4.07
27.	Shellfish, Fresh Or Frozen	0.00	0.28	0.64	1.00	1.93
28.	Soups, Meat, Canned	3.37	39.23	42.77	35.94	54.76
29.	Soups, Pea, Canned	1.09	14.52	19.97	37.58	30.41
30.	Soups, Tomato, Canned	0.37	7.70	11.66	7.39	7.02
31.	Soups, Dehydrated	0.00	10.02	7.98	7.92	7.65
32.	Bread, White	2.12	34.00	76.80	94.88	67.45
33.	Bread, Whole Wheat And Rye	0.00	5.49	6.47	7.43	19.76
34.	Rolls And Biscuits	0.00	3.64	11.63	15.92	10.00
35.	Flour, Wheat	0.28	3.86	10.38	5.17	6.93
36.	Cake	0.19	8.59	25.62	42.52	20.37
37.	Cookies	1.50	18.87	26.00	23.08	15.58
38.	Danish And Donuts	0.00	3.60	5.39	9.53	5.49
39.	Crackers	0.04	4.83	5.14	5.67	3.45
40.	Pancakes	0.00	2.16	2.93	3.37	2.04
41.	Cereals, Cooked Wheat	13.50	13.94	5.72	4.73	6.53
42.	Cereals, Oatmeal	33.12	20.86	19.95	12.26	16.44
43.	Cereals, Corn	1.07	3.42	5.37	3.40	1.82
44.	Cereals, Wheat And Bran	0.09	3.37	3.37	3.35	2.31
45.	Rice	0.00	6.73	13.98	14.56	15.14
46.	Pie, Apple	0.00	2.02	3.87	3.71	9.25
47.	Pie, Other	0.08	3.68	10.35	10.77	11.70
48.	Pizza	0.00	0.12	3.09	5.09	1.74
49.	Pasta	0.00	17.67	36.90	46.99	15.81
50.	Pasta, Ordinary	0.00	10.85	26.24	10.32	13.47
51.	Corn	0.56	9.90	17.60	12.02	8.16
52.	Potatoes, Raw	0.00	0.25	0.00	0.00	0.04
53.	Potatoes, Baked	0.00	2.08	2.95	3.05	4.92
54.	Potatoes, Boiled, Skins On	0.00	2.13	1.81	3.54	5.43
55.	Potatoes, Boiled, Skins Off	7.51	45.22	77.66	100.98	82.11
56.	Potatoes, French Fried, Frozen	0.01	18.46	22.78	33.02	20.68
57.	Potatoes, Chips	0.00	1.64	5.18	7.81	1.31
58.	Cabbage	0.00	2.69	5.05	6.21	10.26
59.	Celery	0.03	1.59	2.43	3.45	8.34
60.	Peppers	0.00	0.05	0.27	0.43	1.28
61.	Lettuce	0.00	2.37	4.49	8.21	12.70
62.	Cauliflower	0.00	0.26	0.11	1.11	1.46
63.	Broccoli	0.87	0.34	1.34	0.20	2.19
64.	Beans	0.32	2.66	4.27	4.49	6.82
65.	Peas	31.10	6.10	6.09	7.66	9.34
66.	Carrots	1.39	8.14	10.34	11.08	14.19
67.	Onion	0.00	0.89	2.45	3.05	6.15
68.	Rutabagas Or Turnip	0.58	2.40	3.51	3.29	5.69
69.	Tomatoes	0.00	3.19	7.47	11.16	17.90
70.	Tomato Juice, Canned	0.00	5.28	4.52	5.64	10.02
71.	Tomatoes/sauce, Canned & Ketchup	0.00	4.91	7.15	8.88	6.40
72.	Mushrooms, Canned	0.00	0.47	0.86	2.11	1.63
73.	Cucumbers	0.00	3.47	8.27	11.27	11.37
74.	Citrus Fruit, Raw	0.00	11.47	24.70	22.29	33.25
75.	Citrus Fruit, Canned	0.00	0.00	0.17	0.04	0.16
76.	Citrus Juice	3.46	34.61	22.54	32.98	35.01
77.	Citrus Juice, Canned	11.82	9.69	12.96	11.05	13.38
78.	Apples, Raw	1.15	26.79	41.38	33.85	20.52
79.	Apple Juice, Canned, Unsweetened	14.98	44.21	26.66	9.65	13.30
80.	Applesauce, Canned, Sweetened	1.45	3.91	8.81	3.16	5.97
81.	Bananas	3.25	12.98	21.42	11.19	12.82
82.	Grapes	0.00	0.82	1.52	2.67	2.94
83.	Grape Juice, Bottled	0.00	5.27	2.52	5.02	2.15
84.	Peaches	0.50	12.25	10.27	6.56	10.17
85.	Pears	73.53	18.10	6.70	4.06	7.73
86.	Plums, Dried Prunes & Canned Plums	0.95	2.15	2.72	2.64	4.74
87.	Cherries	0.00	0.90	1.15	0.88	1.64
88.	Melons	0.00	1.18	7.39	3.82	9.53
89.	Strawberries	0.00	3.01	7.56	5.39	7.75
90.	Blueberries	0.67	0.67	1.00	1.51	1.99
91.	Pineapple	0.00	0.70	1.68	1.66	2.22
92.	Cooking Fats & Salad Oils	0.00	1.23	2.21	3.97	4.95
93.	Margarine	0.02	2.65	6.13	8.34	6.23
94.	Peanut Butter & Peanuts	0.16	2.98	6.08	6.60	3.52
95.	Sugar, White	1.54	7.08	11.66	14.46	19.20
96.	Syrup	3.13	2.89	6.45	5.59	4.94
97.	Jams	0.28	3.55	6.76	9.63	6.14
98.	Honey	1.30	0.86	2.02	1.88	2.17
99.	Puddings	18.13	13.16	8.85	10.59	8.78
100.	Candy, Chocolate Bars	0.16	3.14	5.45	8.10	3.58
101.	Candy, Others	0.01	5.36	8.47	10.39	4.58
102.	Coffee	0.00	6.48	11.99	83.95	347.77
103.	Tea	0.00	8.47	22.20	81.64	354.13
104.	Soft Drinks	2.39	100.33	193.57	240.70	109.91
105.	Alcoholic Drinks, Wine	0.00	0.02	0.73	1.84	23.54
106.	Alcoholic Drinks, Beer	0.00	1.22	1.93	21.44	121.05
107.	Muffins	0.00	0.39	0.53	2.12	1.56
108.	Baked Beans	0.00	3.11	7.27	12.14	8.12
109.	Raisins	0.00	0.50	0.53	1.08	0.62
110.	Wieners	0.00	2.26	6.35	5.45	2.41
111.	Gelatin Dessert	0.09	9.59	7.49	5.98	7.80
112.	Beets	0.00	0.43	1.26	1.00	1.80
Total		821.05	1,492.48	1,833.10	2,109.28	2,299.30
Sample Size		132	1,199	2,086	2,342	7,037

1. These data will be used if it is assumed that the infant is not exclusively breast-fed or not exclusively formula-fed (see text for discussion)
2. Includes 90.50 g of infant formula per day.

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^8.It should be noted that although relevant data concerning occupational exposure, para-occupational exposure (for hobbyists, for example), substance abuse and smoking are sometimes reviewed and presented in Supporting Documents and Assessment Reports for Priority Substances, they are not considered in the estimation of total daily intake since such exposures are highly variable, often not typical of most of the general population and more appropriately addressed under statutes other than CEPA.