Tuesday, December 19, 2006

LA Health Effects Study 1962-1981

I’ve been crawling around some dark and dusty corners of the UNSW library, tracking down some old reports on health effects studies of recycled water. Brushing aside the cobwebs, I found a paper published in 1984 by Dr. Ralph Frerichs from the UCLA School of Public Health (see bottom of this post for the full reference).

Dr Frerichs’ study was undertaken in eastern Los Angeles County of California, which had been intentionally recharging underground drinking-water supplies with treated effluent since 1962. Although water extracted from the recharged system consistently met current drinking water standards, there was concern that potentially hazardous substances may have been either overlooked or not considered due to low concentrations.

The proportion of recycled water in drinking water supplies was (and is) variable in different parts of LA. In order to monitor the health of the population potentially exposed to unknown water contaminants, four separate study areas were identified. In two of the areas (the northwest and central control areas) drinking water did not contain any recycled water. In the third area (low recycled water area) households received less than 5 per cent recycled water. In the fourth area (high recycled water area) households received 5 per cent or more recycled water. During the course of the study (in the mid-1970s), the proportion of recycled water increased to nearly 16 per cent in the high recycled water area and 6 per cent in the low recycled water area. At the time, around 1.2 million people resided with the combined four study areas.

A study that examines the health statistics of a population in order to try to identify causes of illness is called an epidemiologic study. Such a study was undertaken in the four LA areas, starting with data from 1969 and going through until 1980. This part of the study relied on census health data and a local cancer surveillance program which was established in 1972.

In addition, a household survey was conducted in 1981 among approximately 2500 women living in the central control area and the high recycled water area. This survey was added to pick up information about adverse reproductive outcomes such as miscarriages; general indicators of illness such as bed-ridden days; possible confounding effects such as alcohol consumption and cigarette smoking; patterns of water consumption; and general morbidity (illness).

The health and disease outcomes included in the monitoring program are shown below.

Existing Vital and Health Data

Mortality (deaths)
1. Death due to all causes
2. Diseases of the heart
3. All cancers (malignant neoplasms)
4. Cancer of the stomach
5. Cancer of the colon
6. Cancer of the rectum
7. Cancer of the bladder
8. Death due to all other causes

Morbidity (illnesses)
9. All potential waterborne diseases
10. Hepatitis A
11. Shigellosis

Birth Outcomes
12. Low weight birth (less than 2,500 gms)
13. Very low weight birth (less than 1,500 gms)
14. Neonatal deaths
15. Infant deaths
16. Congenital malformations at birth

Cancer Surveillance System Data

Incident Cases
17. Cancer of the stomach
18. Cancer of the colon
19. Cancer of the rectum
20. Cancer of the bladder

Household Survey of Women

Adverse Reproductive or Gynecological Outcomes
21. Infertility
22. Menstrual problems
23. Congenital defects
24. Spontaneous abortions (stillbirth)

Functional Impairment
25. Restricted activity days
26. Bed-disability days
27. Hospital-bed days

The relative incidences of these health effects were statistically analysed in the four study areas. The effects of several confounding variables were controlled for where appropriate, including age, sex, race, age of mother and birth weight.

If the consumption of recycled water contributed to excess disease or death, we would expect the relative incidences to be greatest in the high recycled water area, intermediate in the low recycled water area, and similar to the remainder of LA County in the two control areas. Furthermore, we would expect this dose-response relationship to be more amplified in the later years of the study since the concentration of recycled water gradually increased.

Some minor statistical differences were observed between the study areas, including deaths due to all cancers, cases of shigellosis, very low births, and neonatal mortality. However, for none of these factors, were the differences in a direction that would support the hypothesis that increased concentrations of recycled water contributed to excess disease.

In the household survey, no significant differences were observed between the two groups of women in restricted-activity days, bed-disability days, hospital bed-days, or recent contacts with a health professional. Nor were differences observed in the rate of spontaneous abortions, congenital malformations, menstrual problems, or problems of fertility.

The authors of the study summarised their conclusions as follows:

While we can never ensure the complete safety, it is reasonable to assume that the disease risk attributed to the consumption of reclaimed water has been minimal for persons residing in the high and low recycled water areas in eastern Los Angeles County. This does not mean that there is no risk. Nor does it mean that there will be no risk in the future. Rather, available epidemiologic evidence provides no indication that the reuse of water has had a noticeable harmful effect. If findings in the on-going water characterization study are also negative, the combined investigations should provide strong evidence to both the public and to the responsible governmental officials as to the relative safety of water reuse.

All studies of this type have their limitations (people moving into and out of areas, unidentified confounding factors, limited sensitivity to detect extremely low risks, etc). I know that 1984 -when the paper was published- was a long time ago, but I still think this is a nice piece of epidemiology.

What do you reckon?


Source: R.R. Frerichs “Epidemiologic Monitoring of Possible Health Reactions of Wastewater Reuse”. Journal: The Science of the Total Environment. Vol: 32, Year: 1984, Pages: 353-363.

8 comments:

W.F. Blog said...

I reckon it's inconsistent with Dr Jean Ginsberg's letter to 'The Lancet' 1994

I would like to see a more thorough contemporary study.

Stuart Khan said...

Thanks W.F. Blog,

Sperm density is not an endpoint that was considered in the LA study, so its hard to see how the results are inconsistent.

Dr Ginsburg clearly stated in her letter to the editor (and repeated in later correspondence) “we emphasise that we do not assume that the only environmental factor peculiar to those living the [Thames Water Area] was their water supply”. Significantly, Dr Ginsburg did not attempt to correlate the relative proportions of recycled water ingested by the various ‘cohorts’ to the (minor) sperm variability that she observed (in a very small sample size). For all the information that is provided, it is equally possible that the cohort from outside the Thames Water Valley had consumed a greater proportion of recycled water than the cohort within.

I am sure that Dr Ginsburg would agree that it would be unreasonable to argue that her study demonstrates any relationship between recycled water consumption (especially advanced treated recycled water) and sperm density.

But the bottom line is that I agree with you. I would love to see a more thorough contemporary study. In fact, I would like to see lots of them. Nonetheless, we need to accept that there are limits to what such studies can show.

W.F. Blog said...

... or limits to what we want studies to show.

Who is going to fund research when the base hypothesis is not what governments and corporations want to hear verified?

The base hypothesis being "communities ingesting water from unplanned potable reuse may show negative long term health effects".

Stuart Khan said...

Scepticism is a healthy and admirable trait, WF Blog.

However...the base hypothesis from the study described in this current post was almost exactly the one you have suggested that no-one would fund (except that it is for ‘planned’ IPR rather than ‘unplanned’ IPR). I have also collected a couple of others now, which I may summarise here sometime further down the track.

Believe it or not, governments are genuinely interested in knowing what factors lead to negative health outcomes among populations. There is a purely economic rationalist incentive to know this kind of information. Furthermore, they do tend to fund epidemiologic studies to acquire it; -at least in the wealthier countries.

An Australian epidemiologic study of unplanned IPR would certainly be a useful thing; -perhaps we could lobby for it together? As long as a study relied on pre-existing health data, it need not be as prohibitively expensive as I have previously suggested.

Even still, we would need to accept that the sensitivity of such a study is never going to be great enough to detect the very low-risk health incidences that we would consider to be unacceptable.

Anonymous said...

Governments do not car aboit our health. As long as they get elected they don't care if i grow boobs or get testicle cancer!! Why should we believe studys that are biased????

Stuart Khan said...

Hello Anonymous,

I don’t think you (or I, or anybody else) should believe studies that are biased. I suppose the essential skill is being able to determine which studies are biased and which are not.

I acknowledge that this is not necessarily a simple task...in fact it is quite complicated. I’m afraid I can’t offer you a simple sure-fire method of testing the bias of most studies.

However, if you would like to point out any perceived biases in the studies that I relate, I will be very happy to examine your concerns. I will do what I can to address your concerns and, if possible, seek clarification from the original authors. Nonetheless, I wont always have access to the raw data or to the original investigators. Still, I am prepared to try if you will clearly relate your concerns.

Greg said...

I think we would need to look at how much recycled effluent went into the underground water supply, how long the mixing process took place before the water was withdrawn and what percentage of the total water this attributed to before any study could come up with any sort of substantial evidence that there was no effect on health! IMO acurate testing of this is not possible, there are just too many factors to consider!

Stuart Khan said...

Greg,

I think you have made a very good point and, of course, I agree with you. Proving the absence of health effects is an extremely tough challenge and can never really be achieved. I agree that this study does not prove absolutely that there are no health effects from drinking recycled water, and probably no study ever will.

There are indeed too many variable factors that will have a more significant impact on any population compared to the very tiny risks that we are trying to observe from recycled water.

Of course, the same applies to any water source...its not something peculiar to intentionally recycled water.

Post a Comment