🌿 Lead and its inorganic compounds in workplace air — FAAS (inhalable fraction)

Environment PN-Z-04487

Overview

Lead and its inorganic compounds (with the exception of lead(II) arsenate(V) and lead(II) chromate(VI)), calculated as Pb in the inhalable fraction, have a maximum admissible concentration (NDS) of 0.05 mg/m³ (the regulation of the Minister of Family, Labour and Social Policy of 12 June 2018, Dz.U. 2018 poz. 1286 [Journal of Laws 2018, item 1286]). Lead is strongly poisonous: it damages the nervous, the haematopoietic and the circulatory systems and the kidneys, accumulates in the bones and acts harmfully on reproduction and on the child in the mother's womb; IARC has classified lead and its inorganic compounds in group 2A. Exposure occurs in the manufacture of accumulators, cables, alloys (with tin, copper, antimony, cadmium) and radiological screens and in metallurgy. The method was worked out at CIOP-PIB (Surgiewicz, PiMOŚP 2016, No 3(89)) as the basis of a draft Polish Standard — at present PN-Z-04487:2017-10 — replacing PN-Z-04139.04:1989 (a limit of determination of 0.01 mg/m³, sampling on a set of filters without personal sampling) and PN-ISO 8518:1994 (range 10–200 µg in the sample). It meets the requirements of PN-EN 482 over the range from 1/10 to 2 of the NDS value: the measuring range 0.25–10.0 µg/ml corresponds to 0.0035–0.139 mg/m³ with a sample of 720 l (0.07–2.8 NDS) and to 0.0052–0.208 mg/m³ with 480 l (0.10–4.2 NDS); LOD 0.02 µg/ml, LOQ 0.07 µg/ml, recovery 0.99, total precision 5.31 %, expanded uncertainty 23.06 %. Occupational hygiene laboratories take the samples in accordance with clause 7 of the standard with an inhalable fraction head, a flow rate of 2.0 dm³/min and a volume of 100–1080 dm³; a sample tightly closed and kept at ambient temperature is stable.

Method principle

A known volume of the air tested is drawn through a cellulose ester membrane filter (pore diameter 0.80 or 0.85 µm) placed in an inhalable fraction separator, which allows the samples to be taken by personal sampling (PN-Z-04008-7). The filter is mineralised hot: 3 ml of concentrated nitric acid and 1 ml of 30 % hydrogen peroxide on a hot plate at about 140 °C until the nitrogen oxides have evaporated to dryness, the operation being repeated twice; after cooling 1 ml of concentrated HNO₃ is added for about 30 min, the contents are transferred quantitatively with water into a 10 ml flask, 1 ml of lanthanum chloride solution (spectral buffer; final concentration of La 1 %) is added and the flask is made up with water. Lead is determined by atomic absorption spectrometry with atomisation in a stoichiometric air–acetylene flame at 283.3 nm with deuterium background correction, against a calibration curve of 0.25–10.0 µg/ml (the standards contain 1 % La and dilute HNO₃; zeroing with 0.1 mol/l HNO₃). In parallel a clean filter is mineralised (the blank) and its concentration is subtracted from the result. A twenty-fold excess of Sn, Sb, Zn, As, Cu, Ni and Cd does not affect the result. The concentration in the air X = (C − C0)·V1·k/(V·wm), where V1 = 10 ml, V — the volume of air [l], k — the dilution factor, wm — the recovery factor (1.00 ± 0.05).

Applications

• Control of the sanitary and hygienic conditions at the workplaces of the manufacture of accumulators, cables, alloys and lead products and in non-ferrous metal smelting works
• Assessment of occupational exposure in accordance with the principles of personal sampling (the inhalable fraction) over the range 1/10–2 NDS
• Measurements during work with lead paints, in foundries, during soldering and in the manufacture of lead glass
• Extension to the determination of other metals in the same sample (multi-element FAAS and ICP-AES procedures)

Key parameters

Standard

Standard number

PN-Z-04487:2017-10

Title (PL)

Ochrona czystości powietrza — Oznaczanie ołowiu i jego związków nieorganicznych na stanowiskach pracy metodą płomieniowej absorpcyjnej spektrometrii atomowej

Title (EN)

Air purity protection — Determination of lead and its inorganic compounds at workplaces by flame atomic absorption spectrometry

Step-by-step procedure

1. Sampling

   Calibrate the system according to the instructions of the calibrator for the flow rate required by the manufacturer of the sampler; in accordance with the principles of PN-Z-04008-7 draw at least 480 l of air through the filter in the inhalable fraction head (most often 2 l/min).

2. Mineralisation

   Place the filter in a 50 ml beaker, add 3 ml of concentrated HNO₃ and 1 ml of H₂O₂, heat carefully on the plate at about 140 °C until the nitrogen oxides have evaporated to dryness; repeat twice with the same amounts; after cooling add 1 ml of HNO₃ and leave it for about 30 min.

3. Solution for the test

   Transfer the contents with 5–6 portions of water into a 10 ml flask, add 1 ml of lanthanum chloride solution and make up with water. In parallel mineralise a clean filter in an identical manner (the blank).

4. Calibration curve

   Into seven 10 ml flasks measure out 0.05–2.00 ml of the intermediate solution of 50 µg/ml and 1 ml of lanthanum chloride and make up with HNO₃ (1 + 9) — the standards 0.25–10.0 µg/ml; the eighth flask — the zero sample. Make three measurements of the absorbance of each at 283.3 nm, zeroing with 0.1 mol/l HNO₃; prepare the curve immediately before the determination.

5. Measurement

   Measure the absorbance of the test solution and of the blank under the same conditions; read the concentrations from the curve. Where the range is exceeded dilute the sample with a solution of the same concentration of HNO₃ and of lanthanum, taking the factor k into account.

6. Recovery and calculations

   Check the effectiveness of the mineralisation on six filters onto which 60 µl of the 1 mg/ml solution has been applied (wm = 1.00 ± 0.05). Calculate X = (C − C0)·V1·k/(V·wm) in mg/m³ and compare it with the NDS of 0.05 mg/m³.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Concentrated nitric acid and hydrogen peroxide — work in protective clothing under an efficient fume cupboard; the nitrogen oxides from the mineralisation are toxic
• Lead and its compounds are toxic, carcinogenic (2A) and harmful to reproduction — treat the filters and the solutions as hazardous waste and hand them over to authorised institutions
• Acetylene — the gas installation and the AAS burner in accordance with the instructions for the instrument

Frequently asked questions