Safety Evaluation of Disposable Baby Diapers Using Principles of Quantitative Risk Assessment

Figures & data

1. FIG. 1. Gross view of a baby diaper.

2. FIG. 2. Cross section of a typical baby diaper. NW, nonwoven; SAP, superabsorbent polymer; AQL, acquisition layer; BS, back sheet; CBWL, cellulose-based wicking layer.

3. FIG. 3. Ilustration of diaper “reflux” measurement.

TABLE 2 Typical Diaper Weight Ranges and Change Frequencies (P&G Internal Consumer Usage Data)

Diaper size	1	2	3	4	5
Baby weightrange (kg)	2 to 5	3 to 6	4 to 9	7 to 20	11 to 25
Approximate diaper weight (g)	24	25	33	40	45
Average change frequency (number ofdiapers/day)	6	5 to 6	4 to 5	4	3

TABLE 1 Habits and Practices—Data for Baby Diaper Usage in Different Countries in Asia: Procter & Gamble Consumer Research Data

Country	Surface area (cm^2)	Diapers/day	Average usage period (h)	Average loadingamount (ml)	Reflux for last loading in laboratory test (g)	Average weight of baby (kg)
China	1647	4 to 5	4.8	164	0.12	11.7
	480	3.6	3.17	87 ± 26	0.137	9.53
Korea	1325	5.5	4.4	91	0.15	NA
	1396	5.7	4.2	93	0.17	NA
Japan	1186	6.1	3.9	89	0.09	8.7
Philippines	1566	2.5	6	254	0.12–0.14	9.7
Indonesia	1566	3.1	6	166	0.12–0.14	10.5

Note. NA, not available.

4. FIG. 4. Structure and molecular formula of citral.

TABLE 3 Identification of Weight-of-Evidence No-Expected-Sensitization-Induction-Level (WoE NESIL) for Citral

Name of raw material	CAS number	IFRA standard limit (skin contact products)	LLNA weighted mean EC3 values (μg/cm^2)	NOEL-HRIPT (induction) (μg/cm^2)	NOEL-MAX (induction) (μg/cm^2)	LOEL (induction) (μg/cm^2)	Potencyclassification	WoE NESIL
Citral	5392-40-5	NA	5.7% (1414)	1400	NA	3876	Weak	1400

Note. LLNA, local lymph node assay; NOEL, no-observed-effect level; HRIPT, human repeat insult patch test; LOEL, lowest-observed-effect level. Sources: International Fragrance Association, 2006; The Scientific Committee on Cosmetic Products and Non-Food Products Intended for Consumers, 1999; Lalko and Api, 2008.

TABLE 4 Application of QRA for Citral in Perfumes Used in Diaper Products

WoE NESIL	1400 μg/cm^2
SAF^a	100 (10 × 1 × 10)
AEL	1400/100 = 14 μg/cm^2
CEL	0.000014 μg/cm^2
AEL/CEL	14/0.000014 = 1,000,000
Risk assessment for citral	Acceptable, since AEL > CEL

^aSAF: interindividual variability = 10; this is based upon well-established principles of general toxicology and is meant to reflect not only the average consumer, but also more susceptible sup-populations. Vehicle matrix = 1; matrix is very different from the experimental test conditions. However, it is not expected to be more irritating, and the diaper matrix is an inert material and not skin impactful. Use considerations = 10; in this case, the area is the baby's buttocks, groin, lower stomach, and upper thighs. Skin integrity may be compromised (as in the case of diaper rash). Mucus membrane exposure may occur, along with somewhat occlusive diaper wearing conditions.

5. FIG. 5. Structure and molecular formula of acrylic acid.

TABLE 5 Hazard Profile of Acrylic Acid

Acute toxicity	Irritation—oral and dermal
Irritation/Corrosion	Corrosion—dermal, eyes, and respiratory tract
Sensitization	Not sensitizing
Repeated dose toxicity	Irritation, unspecific
Mutagenicity	Nonmutagenic—Acrylic acid is nonmutagenic in Salmonella and Chinese hamster ovary (CHO) cells, but positive in the mouse lymphoma assay and in the in vitro chromosomal aberration test. However, in vivo acrylic acid did not produce mutagenic effects in either rat bone-marrow cells or mouse germ cells after oral administration. Based on these results, and considering data from structurally related acrylic compounds, it is concluded that acrylic acid is not mutagenic in vivo.
Carcinogenicity	Noncarcinogenic—Studies on animals indicate that acrylic acid is not carcinogenic.
Reproductive toxicity	Not a reproductive toxin—In oral reproductive toxicity studies (rats), no effects on reproductive function (fertility) were observed, but some signs of postnatal developmental toxicity (retarded body weight gain of the pups) were seen following exposure of the parental generation. No gross abnormalities were observed in the offspring. No prenatal developmental toxicity was observed (rats and rabbits, inhalation).

TABLE 6 Application of EBRA to Available Acrylic Acid in Diaper Absorbent Cores

RfD of acrylic acid (U.S. EPA)	0.5 mg/kg/d
Total amount of SAP/pad	15g
Amount of extractable monomer^a	500 ppm (manufacturers' upper limit)
Number of diapers per day	5
Total available acrylic acid per day	500 ppm × 15 g = 7.5 mg/d × 5 = 37.5 mg/d
Weight of baby	8 kg
Total available acrylic acid/kg body weight	37.5 ÷ 8 = 4.7 mg/kg/d
Reflux factor	0.25% (or 0.0025)
Dermal absorption	100% (conservative assumption)
Potential consumer exposure	4.7 mg/kg/d × 0.0025 × 1 = 0.012 mg/kg/d
Margin of safety (MOS) = RfD/consumer exposure	0.5 ÷ 0.012 mg/kg/d = 42

^a500 ppm is the maximum limit of available acrylic acid monomers that suppliers of SAP are currently required to meet, for use in baby diapers.

www.ifraorg.org/Home/Publications/Download-the-IFRA-Amendments/page.aspx/134 International Fragrance Association. 2006. IFRA standard, 40th Amendment: Citral

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Scientific Committee on Cosmetic Products and Non-Food Products Intended for ConsumersOpinion concerning fragrance allergy in consumers.1999 SCCNFP / 0017/98 Final

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LalkoJ.ApiA. M.Citral: Identifying a threshold for induction of dermal sensitizationRegul. Toxicol. Pharmacol.2008516273

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