Cadmium, Arsenic, and glass manufacturing in Portland: What do the test results mean?

Tonight at Cleveland High School (in Portland, OR) the Multnomah County government convened a public meeting to discuss the recent pinpointing of elevated cadmium (Cd) and arsenic (As) levels in Portland to the Bullseye Glass manufacturing facility at 3722 SE 21st. Avenue. I was frankly hoping that the representatives of the Department of Environmental Quality (DEQ) and Oregon Health Authority (OHA) would put the levels DEQ measured of those metals in October into a health context. Unfortunately, they did not, and the meeting degenerated into an expression of public anger that didn't answer many questions.

Fortunately, we have well-established models of cancer risk from the Environmental Protection Agency (EPA) and reference exposures from the California EPA for the threshold of likely health risks in general. Those models and exposures are based on data from industrial use of Cd and As, as well as documented environmental exposures from published studies. In other words, we have an evidence-based context for the numbers DEQ measured in the air outside Bullseye's production facility. In hopes of helping people understand the big question voiced at the meeting tonight ("What do the emissions mean for my family?"),  I've compiled the results from air quality monitoring with those reference levels.

To make things easier to compare, I've put all the exposure data and relevant reference levels in a table with everything in the same units (micrograms per cubic meter).

Let's break these numbers down a bit. First off, the DEQ numbers come from the agency's monitoring station in the parking lot of Fred Meyer corporate headquaters, 120 meters from the Bullseye Glass factory. You can get those numbers here. Note: DEQ reported nanograms per cubic meter, so you have to divide those numbers by 1,000 to get micrograms per cubic meter.

The Oregon DEQ benchmarks are reported here. These numbers are set based on the EPA lung-cancer model, where the benchmark is the level at which exposure would increase cancer risk by 1 in one million for a person who breathed that air for their entire lifetime (chronic exposure).

The EPA cancer risk and CalEPA reference exposures come from this page (arsenic) and this page (cadmium). I used the 1 in 10,000 lung cancer risk estimate from EPA because it was closest to the exposures reported near Bullseye. It's a linear model, so it shouldn't be surprising that you can just multiply the DEQ benchmark by 100 to get that number as well. Note: The CalEPA reference exposures are given in milligrams per cubic meter, so you have to multiply those numbers by 1,000 to get to micrograms per cubic meter.

From a first look, you may notice that the average exposure DEQ measured falls near the 1 in 10,000 risk for lung cancer from the EPA model (it's actually about 1 in 6,300 for As, and 1 in 20,400 for Cd). The averages are also 2-3 times the CalEPA threshold below which no health effects at all are expected.

Hopefully you've noticed something else from the table above: the DEQ benchmarks are quite stringent. They are far below the CalEPA thresholds for any likely health effects at all from inhaling either cadmium or arsenic, and they correspond to a 1 in one million increase in lung cancer risk (based on the EPA models). For some perspective, men have a 1 in 13 chance of developing lung cancer in their lifetime (and a 1 in 2 chance of any cancer), while women have a 1 in 16 lifetime chance for lung cancer and a 1 in 3 lifetime chance for all cancers (check out the data from the American Cancer Society). Taken another way, if one million people lived at the DEQ benchmark, we would expect one lung cancer due to cadmium exposure, and about 70,000 lung cancers from other causes. Even going up to the 1 in 10,000 risk in the table above, you would expect around 50 cadmium-related lung cancers in a population of one million who all lived at the monitoring station, as compared to the 70,000 cases from other causes. Did I say stringent?

It's important to repeat that the data above come from right next to Bullseye. If you go even a short distance away, mixing in the atmosphere will lower the concentration of arsenic and cadmium. DEQ has even published a preliminary map of expected cadmium exposures here, based on relative concentrations of the elements in moss samples collected by the US Forest Service. Here's a screenshot:

These numbers are in nanograms per cubic meter again, so you have to divide by 1,000 to compare with the table. It may help to think of the boundary between the highest two concentrations (around 30 ng/cubic meter) as the average from monitoring (29.4 ng/cubic meter). By the time you get to the Fred Meyer day care, the estimated levels have dropped to about 0.01 micrograms/cubic meter - or right at the CalEPA threshold below which any health effects are unlikely. Farther out, at Cleveland HS or Winterhaven Elementary, levels are more like 0.005 micrograms/cubic meter, half the CalEPA health threshold and in the 1 in 100,000 probability of cancer in an individual due to the cadmium exposure. You may also notice a smaller point-source in north Portland, which looks like it's at Ostrom Glass and Metal Works.

So what's the conclusion?

Even for students at the Fred Meyer day care facility, inhaling the air is unlikely to cause any ill effects at all based on the CalEPA threshold and EPA cancer models. The cancer risk estimate is already down to 1 in 60,000. In other words, if there were 60,000 students in that day care, we would expect one of them to get a lung cancer from Cd exposure. There are in fact approximately 100 children who attend the facility, and they will not breathe this air 24/7 for 70 years (the assumptions of the EPA model). As for other health effects, the exposure looks like it would be right at the CalEPA threshold outside (and probably lower inside).

Further away (for example, in the residential neighborhoods east of 26th Ave. and south of Gladstone St., exposures should be lower. While there are reports of a detectable level of Cd and As in the soil at the day care facility, soil and air tests at Cleveland HS and Winterhaven Elementary ordered by Portland Public Schools did not detect any Cd or As. (I hope to link to those results if and when they are released).

In short, the levels DEQ detected are at or below where one would expect much of an elevation in lung cancer risk or other health consequences. Personally, I don't see grounds to get particularly worried about human health given the numbers that have been reported.

Let me be clear: It would be great to get cadmium and arsenic exposures down to the DEQ benchmarks, especially since they are elements and do not "break down" in the environment the way molecular toxins can. Given the possibility of soil accumulation, DEQ's efforts make sense. I hope that the employees at Bullseye are being evaluated for As and Cd exposure, since their exposures are potentially much higher inside the factory. And re-evaluating the pollution control measures at Bullseye is a no-brainer, since we now know that it is a significant point source for As and Cd. There is lots of work to be done.

However, the community anger expressed at tonight's meeting is, in my opinion, totally unjustified. It was clear from DEQ and Forest Service presentations that sleuthing out the source of Cd and As was an involved process, from DEQ identifying the two elements as more concentrated in monitoring than predicted from modeling known sources, to the Forest Service using a moss and lichen model to establish relative exposures throughout the City, to the DEQ doing targeted monitoring near Bullseye to confirm the source and document the exposure levels. Put simply, government agencies discovered the problem and tracked it to its source before anybody noticed any consequences. To me, that looks like effective detective work on the part of DEQ and USFS. The first commenter, reading a prepared statement from Neighbors for Clean Air, characterized the process as "an abysmal failure of government." While I understand that many of my neighbors are worried and angry, I think we can do better than that.


UPDATES:
As the conversation has broadened to include emissions of hexavalent chromium, I've written another post dealing with that metal.

Also, soil testing results from the nearby daycare have been released, and I've worked through those in another post.

The OR state cancer registry (OSCaR) has released the results of an analysis of lung and bladder cancer in the area around Bullseye glass; here are those results with my analysis.