Measurement of Soil Lead Levels Adjacent to Lead-Sheathed Communications Cables

Introduction

Lead exposure reduction has been one of the most successful environmental health campaigns ever undertaken.¹ However, for the target goal of “zero” micrograms of lead in blood to be met, it will be necessary to go beyond controlling lead-based paint, lead water lines, and consumer products and to seek out and reduce other overlooked exposures.² This paper explores one such source—lead exposure from aerial terrestrial and submarine lead sheathed communications cables (LSCCs).

LSCCs were widely used from the late 1800s to the 1960s³ and ultimately replaced by plastics and other synthetic coverings. The cables were suspended on utility poles (i.e., aerial cables) and when going under water bodies, bundled together as submarine cables. In both aerial and submarine LSCCs, the metallic sheen of new cables quickly oxidizes to a dull lead oxide coating that prevents further corrosion. This coating may be friable and released as cables sway and may be subject to various weather conditions (i.e., wind, rain, snow, and ice). The objective of this investigation was to conduct a preliminary assessment of the extent of soil contamination from submarine and aerial LSCCs and to assess potential risks to children’s health.

Methods

Sampling sites of aerial and submarine cables were chosen at locations identified by a Wall Street Journal investigative report.^4,5 The three submarine sites were in Southeast Louisiana. The aerial sites were in suburban communities in New Jersey (cable length $825\text{\hspace{0.17em}ft}$ long), New York ($650\text{\hspace{0.17em}ft}$), and Pennsylvania ($550\text{\hspace{0.17em}ft}$).

On-site lead in soil analysis directly below and adjacent [$\sim 6\text{\hspace{0.17em}ft\hspace{0.17em}}(\sim 1.83\mathrm{m})$] to LSCCs were taken as well as background readings. Sampling was performed using a direct reading hand-held Niton XL3t X-ray Fluorescence Analyzer (XRF). All XRF readings were taken in soil mode at surface level, with grass and debris pushed aside. Appropriate calibration checks instituted prior to each sampling period. For submarine sites, testing was conducted on dry land at the point where the cable exited the ground. Samples were taken in concentric circles radiating out from the cable until background levels were approached. Results from paired in situ and dried/sieved samples were used to calculate an in situ correction factor.⁶ On average, raw XRF measurements were adjusted 25%–46% upward. Approximately 10% of collected samples were sent to an accredited lead laboratory for quality control. The cutoff for natural vs. anthropogenic lead concentration was chosen based on US Environmental Protection Agency (EPA)/US Geological Survey (USGS) Lead in Soil Background levels.⁷ Readings below the 95% upper confidence limit of background soil lead for the location were excluded from the analysis.

To ascertain the source of lead in soil individual Pb isotopes were measured—namely ${}^{204}\mathrm{lead}\left({}^{204}\mathrm{Pb}\right)$, ${}^{206}\mathrm{Pb}$, ${}^{207}\mathrm{Pb}$ and ${}^{208}\mathrm{Pb}$ at select sites. The ratio of these isotopes to one another is commonly used to fingerprint a particular source.⁸ Samples of lead sheathing were collected using a precleaned handheld wire cutter. Comparison cable lead and soil Pb isotopes were analyzed at the University of Washington’s Isotope Geochemistry Laboratory in Seattle, Washington, for four sites, Pennsylvania, Louisiana, New York, and New Jersey. Detailed analytical procedures are available at Bidwell et al.⁹

Results and Discussion

A total of 315, 209, and 52 XRF readings were taken at the New Jersey, New York, and Pennsylvania sites, respectively (Table 1). In each case, lead concentrations in soil from areas immediately below aerial LSCCs were substantially higher than background levels. A frequency distribution of aerial soil leads is presented in Figure 1.

Table 1.

Lead in soil levels within select New Jersey (NJ), New York (NY), Pennsylvania (PA) and Louisiana (LA) communities with aerial and submarine lead-sheathed communications cables (in $\mathrm{mg}/\mathrm{kg}$ or ppm).

Location	Type	Total Number of readings	No. readings above background	$\text{Mean}\pm \text{SD}$	Readings above $200\text{\hspace{0.17em}ppm}$a	% Readings above $200\text{\hspace{0.17em}ppm}$a	Maximum	EPA background (95% UCL)b	${}^{206}\mathrm{Pb}/{}^{204}\mathrm{Pb}$ backgroundc	${}^{206}\mathrm{Pb}/{}^{204}\mathrm{Pb}$ LSCCc	${}^{206}\mathrm{Pb}/{}^{204}\mathrm{Pb}$ sediment/soilc	Different from background
Site 1 NJ	Below aerial LSCC	315	289	$403\pm 337$	209	72.3 %	3,055	71.3	18.988	19.666, 20.686	18.913, 19.215	Inconclusive
Site 2 NY	Below aerial LSCC	209	200	$268\pm 254$	88	44.0%	1,634	41.0	18.748	19.169	17.516	Inconclusive
Site 6 PA	Below aerial LSCC	52	52	$602\pm 660$	41	78.8 %	4,087	61.4	18.881, 19.059	18.165, 18.160, 18.515	18.182, 18.288, 18.763	Yes
Site 3 LA-D	Submarine LSCC	47	47	$697\pm 866$	31	66.0%	4,151	21.2	NA	NA	NA	NA
Site 4 LA-H	Submarine LSCC	61	61	$159\pm 280$	11	18.3%	2,070	21.2	NA	NA	NA	NA
Site 5 LA-N	Submarine LSCC	53	53	$366\pm 467$	15	28.3%	5,415	21.2	19.151	20.437	20.592	Yes

Note: EPA, US Environmental Protection Agency; LSCC, Lead-sheathed communications cable; NA, not applicable, not measured; NIST, National Institute of Standards and Technology; Pb, lead; ppm, parts per million; SD, standard deviation; 95% UCL, 95% upper confidence limit.

^a On January 17th, 2024, the US EPA Lead in Soil guideline (screening level) was lowered from 400 to $200\text{\hspace{0.17em}ppm}$.

^b US EPA background (95% UCL) data from “Background Soil Lead Survey State Data.”⁷

^c Pb corrected for instrumental mass fractionation to NIST $997205\mathrm{Tl}/203\mathrm{Tl}=2.38714$ by exponential mass fractionation law and to NIST $981=16.9356$, 15.4891, and 36.7006 for 206Pb/204, 207Pb/204Pb, and 208Pb/204Pb, respectively, by sample-standard bracketing. External reproducibility for Pb isotope $\text{analyses}=\pm 250\text{\hspace{0.17em}ppm}$.

Figure 1.

Frequency distribution of lead ($\mathrm{mg}/\mathrm{kg}$) in soil adjacent to lead-sheathed communications cables in three communities [Suburban New York (NY), Suburban New Jersey (NJ), Rural Pennsylvania (PA)]. See Table 1 for data. Note: Bkgrd, background; ppm, parts per million.

The three exposed submarine cables assessed at the Louisiana sites all showed elevated lead in and around the cable. Elevated levels of lead in soil tended to be localized within a radius of a few feet from the LSCC (Table 1).

An analysis of the lateral distribution of soil lead levels directly under the New York LSCC site was taken at the New York site. Eight of the 13 transect sites showed a clear decrease in soil Pb level within a few feet off the aerial cable centerline. The average drop-off in Pb levels was $\sim 35\%$. This seems to confirm the primary contamination point was directly below the suspended cable.

The results of isotopic analysis show that the ${}^{206}\mathrm{Pb}/{}^{204}\mathrm{Pb}$ ratios for the soil sample approach that of LSCC for two of the four sites tested—namely site 5 and 6 (Table 1). The data from the two other sites (seven in New Jersey and eight in New York) were inconclusive. Similar isotopic ratios indicate a common source of elemental lead.

The main finding of this study was that lead from existing LSCCs can be transported from the cables and contaminate surrounding soil and dust. This contamination, in residential areas, has high potential to result in childhood lead exposure. According to the US EPA’s Integrated Exposure Update and Biokinetic Lead Exposure Model, children exposed to a residential level of $\sim 325\text{\hspace{0.17em}ppm}$ in soil would yield a blood lead level of $35\mathrm{\mu }\mathrm{g}/\mathrm{L}$, equal to the current Centers for Disease Control and Prevention (CDC) reference level ($3.5\mathrm{\mu }\mathrm{g}/\text{dL}$). The US EPA has recently lowered its guideline regarding levels of lead in soil for residential properties from 400 to $200\mathrm{mg}/\mathrm{kg}$ (or ppm).¹⁰

Lead contamination from LSCCs is a previously overlooked source of lead exposure in the United States.⁴ Although the exposure pathway may not equal that of lead-based paint or lead-contaminated foods, its impact has yet to be thoroughly explored, and in cases of high exposure sites in residential areas, remediation may be warranted.

Conclusions and opinions are those of the individual authors and do not necessarily reflect the policies or views of EHP Publishing or the National Institute of Environmental Health Sciences.