Sources of contaminants in domestic wastewater: nutrients and additional elements from household products

Overview

A 103-page CSIRO Water for a Healthy Country Flagship report prepared for the Victorian Smart Water Fund (Round 3, Project 5) characterising the concentration of nine priority elements — antimony (Sb), chloride (Cl), cobalt (Co), chromium (Cr, total), fluoride (F), molybdenum (Mo), selenium (Se), Total Kjeldahl Nitrogen (TKN) and total phosphorus (TP) — in 156 household and personal-care products purchased from Melbourne supermarkets in early 2008. The intent of the report is wastewater-management rather than consumer-product safety: the elemental concentrations are converted into weekly per-capita household loads using assumed product dosages and use frequencies (Roberts 2005), then compared against the anthropogenic excretion load to attribute domestic-wastewater pollution between human waste and household-product use. From a heavy-metals occurrence standpoint the analytical-chemistry contribution is the per-category concentration tables for the four panel metals tracked by Heavy Metal Index — antimony (an HMTc Category-1 analyte), chromium (HMTc hexavalent chromium (Cr-VI) is not speciated here; total Cr is reported), and the trace-element panel companions cobalt, molybdenum and selenium — measured on an as-purchased finished-product basis. Antimony was the least-frequently detected element (9.6 % of products, detection limit 5 µg/L); chromium was detected in 64 % of products at concentrations ranging from 0.002 to 6.2 mg/kg. Brand identities (private, market-leader, environmental-label) appear as descriptive columns in the source tables and are stripped here per the Part 12 brand firewall; only product-form-and-brand-class descriptors are retained.

Key numbers

Antimony (Sb) concentration in household products (Table 6, p. 22; units mg/kg of finished product, as-purchased basis; LOD 5 µg/L per Table 4 → ≈0.05 mg/kg for typical 10 % w/v dilution):

Sb was below the 5 µg/L detection limit in every brand of toilet cleaner, disinfectant, sunscreen, soap, hand wash, shampoo, hair colouring, deodorant, dishwashing liquid, dishwashing tablet, rinse aid, fabric softener, soaker, wool wash, and most cleaning and personal-care formulations. Overall detection frequency: 15 / 156 = 9.6 %. The highest single Sb concentration recorded was 0.82 mg/kg in a dishwasher powder; the second highest was 0.47 mg/kg in a laundry powder. Sb was detected in 46 % of washing powder brands and 20 % of laundry liquid brands.

Chromium (Cr, total) concentration in household products (Table 9, p. 28; units mg/kg of finished product, as-purchased basis; LOD 0.5 µg/L per Table 4 → ≈0.005 mg/kg for typical 10 % w/v dilution):

Cr was below detection in all brands of shaving foam, soap bars, toilet cleaners, and one brand of depilatory product. Overall Cr detection frequency: 64 % of the 156-product set. Highest single concentrations: 174 mg/kg in one in-cistern toilet freshener (this is the report’s largest single Cr datum and the highest weekly load product), 6.2 mg/kg in a market-leader hand wash, 3.9 mg/kg in a deodorant, 3.50 mg/kg in a fabric softener and a laundry liquid. The report does not speciate Cr-VI versus Cr-III — total Cr only — so the dataset does not feed the HMTc Cr-VI analyte directly.

Cobalt (Co) concentration in household products (Table 8, p. 26; units mg/kg of finished product; LOD 0.5 µg/L → ≈0.005 mg/kg in typical dilution):

Co was below detection in all brands of laundry powder, soaker, dishwasher detergents, hair colouring, oral care, and deodorants. Cobalt was detected most frequently in bathroom personal-care products: 67 % of conditioners, 73 % of shampoos, 80 % of hand washes, 100 % of body washes. Highest single concentration: 7.6 mg/kg in one dishwashing liquid (note the report median for that category is 0.01 mg/kg — the 7.6 datum is the maximum of one outlier brand). Maximum weekly loads ranged 0.8 mg/pe/wk (in-cistern freshener), 0.56 mg/pe/wk (dishwashing liquid), 0.49 mg/pe/wk (laundry liquid).

Molybdenum (Mo) concentration in household products (Table 11, p. 32; units mg/kg of finished product; LOD 0.5 µg/L per Table 4):

Mo was detected in 29 % of the 156-product set. Below detection in all hair colouring brands. Detection prevalence ≥45 % only in toilet fresheners (86 %), recycled toilet paper (62.5 %), laundry powder concentrates (62 %), dishwasher products (50 %), and shampoos and deodorants (45 %). Maximum estimated weekly Mo load is 0.34 mg/pe/wk (laundry powder concentrate).

Selenium (Se) concentration in household products (Table 12, p. 34; units mg/kg of finished product; LOD 4 µg/L per Table 4 → ≈0.04 mg/kg in typical dilution):

Se detected in 18 % of products (30 / 156). Highest single concentration: 4.6 mg/kg in one anti-dandruff shampoo (selenium sulfide is a known anti-dandruff active). Maximum weekly Se loads: laundry liquid 0.15 mg/pe/wk, anti-dandruff shampoo 0.12 mg/pe/wk, laundry powder 0.09 mg/pe/wk.

Frequency-of-detection summary across the four HMI-tracked panel metals in the 156-product set (Section 4.1 narrative, p. 21): TP 97 % > TKN 84 % > Cl 79.5 % > Cr 64 % > Mo 29 % > F 22.7 % > Co < 30 % > Se 18 % > Sb 9.6 %. Of the HMI panel, antimony is the least-frequently detected; total chromium is the most-frequently detected.

Per-product weekly load attribution (Sections 4.1.1-4.1.7 and Appendix 2; units mg of element per person per week, mg/pe/wk, calculated from concentration × dose × frequency for a one-person household):

Comparative load vs human excretion (“anthropogenic load”) for a one-person household (Executive Summary, p. xiii-xiv):

• Antimony: product load varied 0 - 95× the anthropogenic load; median product load ≈ 9 % of excretion load; laundry and kitchen the dominant product sources.
• Chromium: products generated 50 % - 276× the anthropogenic load — i.e., for most product brand mixes household products exceeded human-waste contribution to wastewater Cr, often by ≥ one order of magnitude.
• Cobalt: product load < 0.25× to 13× the anthropogenic load (~25 % to 1300 %).
• Molybdenum: product load up to 97 % of anthropogenic load.
• Selenium: product load up to 60 % of anthropogenic load.

The framing for these comparisons is wastewater-management (the load arriving at Melbourne sewage plants), not consumer exposure. The percentages are not bioavailable-dose comparisons.

Methods (brief)

Sample acquisition. 156 unique household and personal-care product brands were purchased from major Melbourne supermarkets during February-March 2008. For each product category at least one private/supermarket-label brand, one market-leader brand, and (where available) one brand carrying an “environmentally friendly” / “natural” label were included; one sample per brand. The brand mix is enumerated in Sections 3.1.1 (cleaning), 3.1.2 (dishwashing), 3.1.3 (laundry), 3.1.4 (personal care). Brand identities appear in the underlying product-by-product appendix tables but are not reproduced here per Part 12.

Sample preparation and digestion. Liquid products were diluted 1:10 v/v in deionised water (or analysed in their original state for nutrient analysis). High-organic-content solids (e.g., toilet paper) were dry-ashed: a 5 g sample was ashed in a covered crucible in a muffle furnace at 450 °C for one hour or until mass stabilised. Ashed and diluted samples were then acid-digested with high-purity nitric acid (Fluka TraceSelect) and hydrochloric acid (BDH AnalaR) at 95 °C following APHA/AWWA method 3030E, with acid added in 5 mL increments; digests were transferred to a 100 mL volumetric flask and made to volume with deionised water. Reagent blanks were prepared for each 20-sample batch.

Metal analysis instrumentation. Antimony, cobalt, chromium, molybdenum, and selenium were quantified by inductively coupled plasma mass spectrometry on a Thermo X-series ICP-MS. The other element panel members (chloride at WSL115 ion chromatography in an external NATA-accredited lab; fluoride by APHA 4500-F ion-selective electrode; total Kjeldahl nitrogen by APHA 4500-N Org B at a NATA lab; total phosphorus by APHA 4500 at the CSIRO Highett laboratory) are reported separately and are not the HMI-relevant analytes. The report cites a parallel ICP-AES instrument (Varian Liberty Series II) but does not state explicitly which panel metals were apportioned between ICP-MS and ICP-AES; the text in Section 3.2.1 names ICP-MS specifically for Sb, Co, Cr, Mo and Se, and that is the assignment carried here. The report does not name a certified-reference material, recovery percentage, or interlaboratory comparison for the Sb/Co/Cr/Mo/Se panel; calibration is documented only via method-detection-limit values (Sb 5 µg/L, Co 0.5 µg/L, Cr 0.5 µg/L, Mo 0.5 µg/L, Se 4 µg/L, all in the prepared digest).

Concentration calculation. Element concentration in the finished product (mg/kg) was computed as Conc_product = Conc_measured × V_sample / M_product × 10³, where Conc_measured is the digest concentration (mg/L), V_sample is the volume analysed (L) and M_product is the mass of product tested (g). Geometric mean and median across all brand samples in each product category were the central-tendency statistics reported in Tables 6-15.

Load calculation. Per-capita weekly mass load was estimated as M_week = f × dose × Conc_product, where f is the product-use frequency per week and dose is the manufacturer-recommended per-use dose (kg). Frequency and dose assumptions for a one-person household are tabulated in Table 5 (e.g., shampoo 5 g × 5.3 /wk; laundry powder 126 g × 3 /wk; dishwasher powder 60 g × 1.8 /wk; toothpaste 3 g × 14 /wk; deodorant 0.2 g × 7 /wk). Loads are presented in Tables 28-36 of Appendix 2.

Implications for HMI / HMTc

• Antimony in detergents is real but low-frequency. The 9.6 % detection frequency across 156 mixed household and personal-care products, with a concentration ceiling of 0.82 mg/kg in dishwasher powder and 0.47 mg/kg in laundry powder, is consistent with the source’s own characterisation of Sb as “a minor contaminant in household products” (Section 4.1.1, p.22). Per-capita weekly Sb load is under 0.18 mg/pe/wk even for the highest-Sb laundry-powder brand. The data feed the Sb panel cell on Laundry detergents (liquid, powder, pods/sheets, delicates), Automatic dishwasher detergents, Dish soaps (manual dishwashing) (below detection in all 6 manual liquid brands tested), Toilet bowl cleaners, Floor cleaners (hard surface) (Sb detected in one of four floor cleaners at 0.07 mg/kg), Fabric softeners (liquids and sheets) (below detection in all 7 brands), Toothpaste (Cat 2) (one of nine brands at 0.15 mg/kg).
• Chromium pattern is dominated by one in-cistern outlier. The 174 mg/kg Cr datum in one in-cistern toilet freshener — three orders of magnitude above the next-highest household-product Cr value — drives the 35.8 mg/pe/wk weekly Cr load attributed to in-cistern fresheners. The provenance of the 174 mg/kg figure is plausibly a chromate dye in the cistern-water-staining formulation (the report does not state this explicitly). For HMI synthesis the in-cistern category should be evaluated separately from the rest of the chromium panel because of this outlier, and the absence of Cr-VI speciation means the Cr-VI HMTc cell cannot be informed by this dataset.
• Cobalt occurrence in personal-care wash products. Co was detected in 67 % of conditioners, 73 % of shampoos, 80 % of hand washes, and 100 % of body washes — the most frequently-Co-detecting categories in the panel. Concentrations were low (≤7.6 mg/kg) but the prevalence-across-brands pattern is consistent with Co being a trace impurity of dye, surfactant, or fragrance components rather than a category outlier. The dataset informs the Co panel cell on Shampoo (general adult), Conditioner (general adult, rinse-out), Hand soap (liquid and bar), Body wash/shower gel.
• Selenium-sulfide anti-dandruff shampoos. One brand of anti-dandruff shampoo recorded 4.6 mg/kg Se, by far the highest single Se value in the dataset. Selenium sulfide is a well-known anti-dandruff active ingredient (1-2.5 %); 4.6 mg/kg is two orders of magnitude below a labelled selenium-sulfide active concentration, so this brand presumably uses an alternative anti-dandruff active and the 4.6 mg/kg represents a trace impurity rather than a labelled Se ingredient. The dataset feeds Shampoo (general adult) (anti-dandruff sub-segment) Se panel cell.
• Molybdenum trace-level signal in laundry powder and cistern products. Mo was concentrated in laundry powder concentrates (62 % detection, median 0.56 mg/kg, max 1.35 mg/kg) and toilet fresheners (86 % detection in cistern category). Loads remain below 0.34 mg/pe/wk for any single product. Feeds Laundry detergents (liquid, powder, pods/sheets, delicates) and Other household specialty cleaners (by functional use-case) Mo panel cells.
• Brand-class signal (private vs market-leader vs environmental-label). The report’s most useful brand-class observation is that environmental-label brands generally carried lower phosphorus than the category mean but no consistent across-the-board pattern emerged for the trace metals. For Sb, Cr, Co, Mo, Se there is no environmental-label-versus-conventional advantage reliable across categories. This finding constrains the consumer-substitution lever for trace-metal load reduction and is the kind of evidence HMTc Category-13 (Cosmetics) market-ratcheting decisions need to reference.

Related evidence

• Antimony
• Chromium
• Cobalt
• Molybdenum
• Laundry detergent boosters/additives
• Rinse aids
• All-purpose cleaners
• Bathing soaps
• Deodorants (sticks, roll-ons, gels, creams, wipes, sprays)
• Sun/suntan products (including spray, self-tan, airbrush)
• Body/hand leave-on skin care
• Face/neck leave-on skin care (moisturizers, serums, night creams, leave-on masks)
• Facial cleansers (foaming, cream, gel, oil, micellar)
• Shaving cream/gel/foam
• Mouthwash/oral rinse
• Permanent hair dyes/tints (remain in hair after application)
• Hair dye/color rinses (rinse-off after processing)
• Hair removal products (depilatory creams)
• Nickel, Cobalt and Chromium in Consumer Products: Allergic Contact Dermatitis
• Assessment of the Content of lead (Pb), cadmium (Cd), nickel (Ni) and Cr in Soaps and Detergents from Akure, Nigeria

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